Human Biology

Chapter 40

Introduction to Animal Structure and Function

A. Levels of Structural Organization

1. Cell is the lowest level of organization

2. Tissue is next in line composed of cells

3. Organs are next composed of tissue usually layers of tissue

4. Organ systems is last composed of organs and carries out major body functions

B. Tissue

1. Epithelial Tissue

a. Sheets of tightly packed cells

b. Lines outside of body, organs and other cavities

c. Prevents mechanical injury, invasive microorganisms, fluid loss

d. Simple epithelial has a single layer of cells, Stratified epithelial has a multiple layer

e. Cuboidal is shaped like dice, Squamous is flat like floor tiles, columnar is bricked shaped

2. Connective Tissue

a. Binds and supports other tissue

b. Loose connective tissue bids epithelial to other tissue holding organs in place

c. Fibroblasts and macrophages are found throughout the loose connective tissue that help protect the body

d. Adipose tissue is specialized form of loose connective tissue that stores fat

e. Fibrous connective tissue include tendons and ligaments

f. Cartilage is composed of collagenous fibers

g. The skeleton of most vertebrate is made of bone which is composed of mineralized connective tissue

h. Blood extracellular matrix is plasma, (water, salts, proteins) erythrocytes, (red blood cells) and leukocytes (white blood cells)

3. Nervous Tissue

a. Nervous tissue senses stimuli and transmits signals from one part of the body to another

b. The functional unit of the nervous tissue is the neuron or nerve cell

4. Muscle Tissue

a. Muscle tissue is composed of long cells called muscle fibers that contract when stimulated by nerve impulses

b. Skeletal muscle is associated with voluntary movements

c. Cardiac muscle forms the contractile wall of the heart

d. Smooth muscle is associated with involuntary movements, located in the digestive tract, bladder, arteries, and other internal organs

C. Organs

1. Organs are suspended by sheets of connective tissue called mesenteries

2. Mammals have a thoracic cavity that houses the heart and lungs that is separated from the lower abdominal cavity by a sheet of muscle called the diaphragm

D. Organ System

1. Composed of groups of organs that work together to carry out the major body functions of nearly all animals

E. Bioenergetics

1. Food is digested by enzymatic hydrolysis and energy containing molecule are absorbed by body cells

2. The energy ATP enables the organ systems to carry out life functions and maintain animal life

3. Animals are constantly exchanging energy with the environment

4. Physiologist call learn a lot from studying animals metabolic rates of animals and the amount of energy they need to survive

5. Energy is measured in calories (cal) or kilo-calories (kcal)

6. Metabolic rate is the amount of energy used in a unit of time

7. Breathing and heart beats take minimal amounts of energy while strenuous exercise use large sums of energy

8. Some factor that affect metabolic rate include, age, sex, size, body temperature, oxygen availability and hormonal balance

9. Basal metabolic rate (BMR) is number of calories burned while lying motionless

10. Standard metabolic rate (SMR) is the metabolic rate of resting, fasting, and non stressed ectotherm

11. Metabolic rate per gram is inversely related to body size among animals

12. This means one calorie consumed by is mouse is equivalent to 10 calories consumed by an elephant

F. Body Plans And The External Environment

1. Body Plan, Design

a. Body plan or design refers to the animals size and body shape

b. The body plan affect the way animals interact with the environment

2. Physical Support

a. The larger and heavier the animals the greater demand for support

b. Body posture or the position of the legs relative to the body plays an even more important role in support

3. Body Size and Shape

a. The size and shape of the animal affects how it exchanges energy and materials with the environment

b. Organisms with only a few layers of cells have to be bathed in water

c. These organism’s cardiovascular system is open both inner and outer

d. The whale is an exception to this despite its size the whale’s outer cells must be bathed in water

e. Animals that don’t need there outer cells bathed in water are capable of living on land

G. Regulating The Internal Environment

1. Interstitial fluid is the internal environment of vertebrates

2. This fluid exchanges nutrients and waste

3. Animals are always trying to maintain homeostasis or a steady state

4. Three functional component of homeostasis

a. The receptor detects the change

b. The control center interprets the information sent by the receptor

c. The effectors carries out the appropriate response as directed by the control center

5. An example of the body carrying out this process is sweating

6. The body senses the internal temperature is raising so it starts to sweat to cool down

Chapter 41

Animal Nutrition

A. Nutritional Requirements

1. The nutrients that are needed must satisfy the tree needs

a. Chemical energy

b. Organic raw material used in biosynthesis

c. Essential nutrients the animal is unable create on its own

B. Homeostatic Mechanisms Manage an Animals Fuel

1. When an animal takes in more calories than it uses the body stores the excess

2. In humans the liver and muscle cells stores the excess calories as glycogen

3. Metabolism helps maintain a homeostasis

4. Undernourished animals occurs when the animal does not have enough calories

5. The body will break down its own proteins to compensate, muscles shrink and the brain can become protein deficient

6. Over nourishment is a lot more common especially in the U.S.A

7. This cause the body to store the excess calories leading to obesity

8. Leptin a hormone that is secreted by the adipose cells

9. Lack of leptin lets the brain know the body needs nutrients

C. An Animals Diet Must Supply Essential Nutrients and Carbon Skeleton for Biosynthesis

1. An animal’s diet must provide fuel for the cells but also raw materials used in biosynthesis

2. Lack of these essential nutrients is malnourished

3. Four classes of essential nutrients

a. Essential amino acids have to be acquired in a prefabricated form, eight amino acids are essential in humans

b. Essential Fatty acids are fatty acids the body cannot make on its own, unsaturated fatty acids

c. Vitamins are organic molecules that help with major functions in the body

d. Minerals are inorganic molecules such as calcium and iron

D. Food Types and Feeding Mechanisms

1. The three dietary categories are Herbivores, Carnivores and Omnivores

2. Suspension feeder sift through food particles in the water

3. Substrate feeders are on or live in their food source (Leaf Minors)

4. Deposit feeders eat their way through their food (Earthworm)

5. Fluid feeders suck the nutrients from the host (Mosquitoes)

6. Bulk feeders eat large quantities of food at a time (Python)

E. Overview of The Food Process

1. The four main stages of food processing

a. Ingestion is the first process and it’s the act of eating

b. Digestion is next the process of breaking the food down, using enzymatic hydrolysis, into molecules small enough for the body to absorb

c. Absorption is third and is when the body absorb the molecules such as amino acids and simple sugars

d. Elimination is the undigested food passes through the digestive system and exits the body

2. Intracellular digestion is the digestion or break down of food inside the vacuoles of the cell without digesting the cells own cytoplasm

3. Extracellular Digestion

a. This occurs inside compartments that are continuous through passages, these compartments are called gastrovascular cavities

b. The complete digestive tract or alimentary canals are the tubes in which food travels to carry out the food process

F. The Mammalian Digestive System

1. This digestive system consist of alimentary canals in which peristalsis or rhythmic waves of contraction of muscles pushes the food along

2. Sphincters are ring like calves that regulate the passage of food through the alimentary canals

3. Accessory glands include the salivary gland, the pancreas, and the liver

G. The Oral Cavity

1. Physical and chemical digestion occurs, teeth and saliva

2. The presence of food in the mouth causes a nervous reflex the secretes saliva

3. Salivary amylase helps digest carbohydrates which are the body’s main source of chemical energy

H. The Pharynx

1. More commonly known as the throat, the pharynx is the intersection that leads to the esophagus and the trachea

2. The epiglottis is a flap the prevents food from going down the trachea

I. The Esophagus

1. Peristalsis squeezes the food through the esophagus from the pharynx to the stomach

J. The Stomach

1. Gastric juice is secreted in the stomach to break down food

2. Parietal cells secrete hydrochloric acid into the gastric juice with a pH of 2 that is strong enough to dissolve iron nails

3. Chief cells secrete pepsin is also in the gastric juice, pepsin is an enzyme that begin the hydrolysis of proteins

4. Every 20 minutes the stomach churns the food turning the nutrients into acid chime

5. The pyloric sphincter is located at the opening of the stomach to the small intestine and slowly releases some of the chime into the small intestine, a meal takes about two to six hours

K. The Small Intestine

1. The small intestine is the site where most of the enzymatic hydrolysis of the macromolecules in food occurs, also absorbs nutrients into blood stream

2. Duodenum is the first 25 cm of the small intestine where acid chime mixes with digestive juices from the pancreas, liver and gallbladder

3. Carbohydrate digestion begins in the oral cavity and continues to the small intestine

4. Pancreatic amylase hydrolyze starch, glycogen, and smaller polysaccharides into disaccharides and maltose

5. Protein digestion is completed in the small intestine that was started by pepsin in the stomach

6. Nucleic acid digestion involves nuclease to hydrolyze DNA and RNA

7. The nucleotides are broken down further into nucleosides

8. Fat usually reaches the small intestine undigested

9. Bile salts from the gallbladder is secreted in the small intestine to keep them from coalescing in a process called emulsification

10. Lipase then hydrolyzes the fat molecules

L. Absorption of Nutrients

1. For nutrients to by absorbed they must cross the lining of the digestive tract

2. Villi are fingerlike projections and microvilli are microscopic appendages that help with the absorption of nutrients

3. Nutrients are absorbed through the intestinal epithelium and across the unicellular epithelium of the capillaries and lacteals

4. Chylomicrons are fats and cholesterol coated with special proteins

5. The hepatic portal vessel leads nutrients directly to the liver at a rate of 1L per minute

M. Hormones Regulate Digestion

1. Hormones are released in the duodenum to make sure digestive secretion are only present when necessary

2. The hormone gastrin is releases in the circuloatory system, when the gastrin circulates back the stomach wall it stimulates additional gastric juices

3. Enterogastrones are hormones secreted in the wall of the duodenum

4. Chyme that enters the duodenum causes the cells to release secretin

5. Cholecystokinin is a hormone secreted when there is the presence of a fatty acid or amino acid and signals the release of pancreatic enzymes

N. The Large Intestine

1. Also called the colon

2. A major function is to reabsorb water about 90% of water is absorbed

3. Bacteria live in the colon including Escherichia coli commonly known as E. coli

4. Cellulose has no nutritional value for human but it helps move feces along the colon

5. The rectum stores feces until the can be eliminated, there are two sphincters on opposite sides of the rectum

O. Evolutionary Adoptions of Digestive Systems

1. Carnivores, Herbivores, and Omnivores all have adapted to fit their diets

2. Herbivores generally have longer digestive tracts relative to the body size because plants have cell walls which are more difficult to digest

P. Symbiotic Microorganisms help Nourish many Vertebrates

1. Many herbivores have bacteria and protest living inside the digestive tract helping digest cellulose

2. Sheep and cattle are ruminants and have the most elaborate adaptations for their plant based diet

Chapter 42

Circulation and Gas Exchange

A. Circulation in Animals

1. Diffusion of chemical is not adequate and is too slow, the circulatory system transports the chemicals throughout the body

2. Oxygen inhaled diffuses into the blood stream where the blood circulates delivering oxygen throughout the body

3. Carbon dioxide diffuses in the opposite direction as the blood

B. Gastrovascular Cavity or a Circulatory System for Internal Transport

1. Gastrovascular Cavity

a. In a hydra and other cnidarians have a body wall two cells thick enclosing the central gastrovascular cavity

b. The gastrovascular cavity serves both in digestion and in distributing substances throughout the body

c. Planarians and other flatworms also have a gastrovascular cavity that exchanges substances with environment

2. Open and Closed Circulatory Systems

a. A gastrovascular cavity would not work out in organisms with many layers of cells

b. An open circulatory system occurs in insects and arthropods where the blood baths the organs directly

c. A closed circulatory system the blood is confined to vessels

C. Vertebrae Phylogeny is Reflected in Adaptations of the Cardiovascular System

1. Cardiovascular system consists of the heart blood vessels and blood

2. The heart has an atrium, a chamber that receives the blood returning to the heart and two ventricles, chambers that pump the blood

3. Arteries carry blood away from the heart to the organs

4. Within the arteries are arterioles, small vessels that carry blood to the capillaries

5. Capillaries are microscopic vessels

6. Capillary beds are networks of capillaries

7. Capillaries come together into the vein

8. Veins return blood to the heart

9. The oxygen rich blood is carried all over the body, the oxygen poor blood returns to the right atrium by means of the veins in a systemic circuit

10. Double circulation pumps the blood twice, a second time after it loses pressure in the capillaries

D. Double Circulation in Mammals Depends on the Anatomy and Pumping Cycle of the Heart

1. The human heart is about the size of a clenched fist and is made up of mostly cardiac muscle tissue

2. The atrioventricular (AV) valve prevents blood from flowing back into the atria

3. Semilunar valves prevents blood from flowing back into the ventricles

4. Pulse is the rhythmic stretching of the arteries causes by pressure of blood

5. By taking your pulse you can find your heart rate, the number of heart beats in a minute

6. The cardiac cycle is a contraction which pumps blood and then relaxes to fill back up with blood

7. The sinoatrial (SA) node is also called the pace maker because it controls the heart rhythm

8. Electrocardiogram detects the electrical impulses with electrodes placed on the skin

9. The SA controls the pace of the heart but two nerves control the SA one slows it down the other speeds it up

E. Structural Difference Between arteries, Veins and Capillaries

1. Capillaries have only the endothelium and basement membrane

2. Veins and Arteries have elastic layer of connective tissue a middle layer of smooth muscle and the endothelium

3. Endothelium is single flattened cells with minimal resistance for blood to easily flow through

4. Arteries have thicker outer and middle layer than veins for strength

F. Blood Flow Velocity

1. Blood travels at the rate of 30 cm/second in the aorta but only .026 cm/second in the capillaries

2. The law of continuity states that as the diameter of a pipe flowing with water the velocity of the water changes

3. A smaller diameter increases the velocity and vice versa

4. This is true also in blood flow, although the capillaries are much smaller in diameter then the aorta all the capillaries combined are much larger

G. Blood Pressure

1. Blood pressure is the hydrostatic force the propels blood through the vessels

2. Blood pressure is much greater in the arteries than the veins

3. Peripheral resistance cause there to be pressure even during diastole

4. Stress as well as physical activities cause nervous and hormonal response that constrict blood vessels raising blood pressure

H. Blood Flow Through Capillary Beds

1. Capillaries are filed with blood 5% to 10% of the time

2. The capillaries in the brain, liver, heart and kidney are usually filled

3. Smooth muscles controlled by nerve signals and hormones regulate the blood distribution to the capillaries

4. Blood supply to the capillaries vary depending on timing

5. If it is after a meal the capillaries near the digestive tract will receive more blood

I. Capillary Exchange

1. The transfer of important fluid such as blood, interstitial fluid, and other molecule can be done one of two ways

2. Blood and interstitial fluid are carried across the endothelial cells in vesicles

3. Molecules like oxygen diffuse through the membrane of the endothelial cells

J. Lymphatic System

1. Approximately 4 liters of fluids are lost each day from the capillaries

2. The lymphatic system returns this lost fluid and proteins to the blood

3. Lymph is the fluid recovered by the lymph capillaries mixed in with the capillaries of the cardiovascular system

4. Lymph nodes are connective tissue filled with white blood cells

5. When the body is fighting infecting theses cells multiply to fight and become swollen

K. Plasma

1. Blood is suspended in the liquid matrix plasma

2. Proteins in the plasma help prevent pH changes and maintain osmotic balance

3. Blood plasma also contains proteins the help clot leaks

4. Plasma also transports nutrients, metabolic waste, respiratory gases and hormones

L. Cellular Elements

1. There are three types of cells in the plasma red blood cells, white blood cells and platelets

2. Red blood cells also called erythrocytes are a lot more abundant then the other two types

3. The main purpose of the red blood cells is to carry oxygen

4. Red blood cells lack a mitochondria so the generate their ATP through anaerobic respiration

M. Stem Cells

1. Erythrocytes, leukocytes, and platelets wear out every 3 to 4 months and need to be replaced

2. Pluripoten stem cells create these new cells

3. The pluripoten stem cells are created the red marrow of bone

4. If Tissue is not receiving enough oxygen, the kidney creates erythropoten

5. Erythropoten then signals the marrow to make more pluripoten which will be used to make erythrocytes

6. Scientist have been able to grow pluripoten cells in a laboratory and are trying to treat human illnesses with is such as leukemia

N. Blood Clotting

1. Fibrinogen is the in active form of what causes blood clots

2. Fibrin is the active form

3. Platelets release clotting factors that signal a chain reaction to form the clot

4. Hemophilia is a disease characterized by excessive bleeding from minor cuts and bruises

5. Thrombus is when fibrin coagulates within the blood vessels

6. This is most likely to occur in people with cardiovascular diseases

O. Cardiovascular Diseases

1. Cardiovascular disease is the leading cause of death in the U.S. usually resulting in stroke or heart attack

2. Heart attack is caused by the death of cardiac muscle tissue resulting from blockage of blood and oxygen to the heart

3. Stroke is death of nervous tissue in the brain

4. Atherosclerosis is the sudden stroke or heart attack usually brought on by impaired arteries

5. Arteriosclerosis also called the Harding of the arteries is when plaque buildup becomes hardened in the arteries by calcium deposits

6. Hypertension or high blood pressure promotes Atherosclerosis as well as heart attack and stroke

7. Low density lipoproteins enables cholesterol to move within the blood stream

8. High density lipoproteins help reduce cholesterol in the blood stream

P. Oxygen of Cellular Respiration

1. Animals require a continual supply of oxygen (O₂) for cellular respiration

2. Respiratory medium is the source of the oxygen so air for terrestrial animals and water for aquatic animals

3. Respiratory surface is where oxygen diffuses into the cells and carbon dioxide diffuses out

4. Some animals like worms use their outer skin as its respiratory surface

5. Gills, Trachea, and Lungs are the three most common respiratory organs

Q. Gills

1. Gills have various shapes designed and specialized for gas exchange

2. Oxygen concentration in the water is much less then in air so gills have to be efficient in bringing in oxygen

3. Ventilation helps this process by increasing the flow of the respiratory medium over the respiratory surface

4. Blood flows in the opposite direction as the water current make a more efficient exchange this is called countercurrent exchange

5. Gills will not work on land they need to be bathed in water or else they

6. will collapse

R. Trachea and Lungs

1. The trachea is also called the wind pipe

2. Oxygen and carbon dioxide diffuse quicker than in water terrestrial animals do not need gills

3. The tracheal system is made up of many air tubes that spread throughout the body

4. The largest tube is the trachea and the smallest extend to all the cells

5. When an animal is moving and has a higher metabolic rate more oxygen is needed and the air tubes expand like bellows

6. The lungs are located in the thorax or chest

7. The lungs are not in direct connection to the rest of the body

8. The lungs are mostly in charge of breathing

S. Mammalian Respiratory System

1. Air enters through the nose or mouth where it is warmed and humidified

2. Then the air travels to the larynx that controls the epiglottis and directs food down the esophagus and air down the trachea

3. When air is exhaled and exits the body it pass through the voice box which is voluntary muscles the vibrate to make sounds

4. Then air moves into the trachea or wind pipe

5. The trachea splits into two bronchi each leading to a lung

6. Inside the lung the bronchus splits into many bronchioles

7. At the end of the bronchioles are alveoli which serve as respiratory surface

T. Ventilating the Lungs

1. Vertebrae ventilate the lungs by inhaling and exhaling which is called breathing

2. Frogs breathe through a process called positive pressure breathing, where its oral cavity enlarges filling up with air and forces air down the trachea

3. Mammals breath in a process called negative pressure breathing, lungs act like a suction pump pulling air in

4. The diaphragm is a sheet of muscle extending across the bottom of the ribcage

5. The diaphragm separates the thoracic cavity from the abdominal cavity and performs an important function in respiration

6. Tidal volume is the volume of air the animal inhales and exhales

7. Vital volume is the volume during forced breathing inhaled and exhaled

8. Residual volume is the air left after forcefully blowing air out

9. Birds have a more complex ventilation system then other animals

10. Instead of lungs they have parabronchi in which air flows constantly in one direction

U. Breathing Control Center in The Brain

1. Holding breath can be voluntary for a short time but for the most part it is automatic mechanisms the regulate the breathing

2. The breathing control centers are located in the medulla oblongata, and the pons

3. The medulla maintains homeostasis by monitoring the CO₂ level in the blood

4. Oxygen levels do not affect breathing too much unless extreme levels are reached

V. Oxygen and Carbon Dioxide Transport

1. Respiratory pigments carry oxygen in the blood stream

2. The respiratory pigment in most vertebrae is hemoglobin

3. Hemoglobin has an iron atom as its center and caries four molecules O₂

4. Hemoglobin also helps transfer CO₂

5. Carbon dioxide first reacts with water to form

6. It then dissociates into hydrogen ions attached to various sites on hemoglobin

7. CO₂ is also converted into bicarbonate which diffuse into plasma

W. Mammals Stockpiling Oxygen and Consume It Slowly

1. The Wendell Seal can swim to depths up to 500 m and can remain submerged in water for over an hour

2. Compared to humans the seal can take in twice as much oxygen proportionally

3. The seal also has a greater amount of myoglobin which is a oxygen storing protein

Chapter 43

The Body’s Defenses

A. Defense Against Infection

1. The skin and mucus membrane are the first line barriers to infection

2. Bacteria and viruses can not normally penetrate skin although minor abrasions allow them pass through

3. Mucous membrane line the digestive, respiratory, and genitourinary tract blocks the entrance of harmful microbes

4. Lysozyme is an antimicrobial protein that destroys many bacteria in the respiratory tract

5. Microbes in food and water, or in swallowed mucus have to deal with the highly acidic stomach

6. Despite the stomachs acidity there are few exceptions that can survive it such as hepatitis A virus

B. Phagocytic and Natural Killer Cells

1. Phagocytosis is the engulfing of invasive organisms by certain kinds of white cells

2. Neutrophils make up around 60% of white blood cells

3. Damaged cells send a signal to the neutrophils and they come and destroy the invasive microbes

4. Monocytes make up 5%, but provide a more effective phagocytic defense

5. Tissue macrophages are the largest phagocytic cells, the live long and are very effective

6. Some bacteria have an outer layer that the macrophages are unable to penetrate allowing them to even reproduce inside the macrophage

7. 1.5% of white blood cells are eosinophils whose main goal is to defend against the larger parasitic invaders

8. Natral killer (NK) cells are not phagocytic

9. They do not attack microorganisms directly but the destroy the virus infect body cells to prevent a tumor

C. The Inflammatory Response

1. Physical injury or the presents of a microorganism causes an inflammatory response

2. The inflammation increases the blood flow the injured area

3. This causes redness as well as heat

4. Basophils and mast cells found in connective tissue produce histamine

5. Histamine is released into the body in response to an injury

6. White blood cells as well as damaged tissue release prostaglandins which increase blood flow

7. Blood clotting is the first step in the repair process preventing microbe from spreading

8. Phagocyte migration usually begins within an hour and is mediated by chemical factors called chemokines

9. Toxins in the body can raise the body temperature causing a fever

10. Some white blood cells then release pyrogens to set the body’s temperature at a higher temperature

D. Antimicrobial Proteins

1. Around 20 serum proteins complete a cascade of steps to the lysis of microbes theses 20 proteins are known collectively as the complement proteins

2. Virus infected cells secrete interferons, theses interferons go to neighboring cells to stop the spread of the virus

3. The body’s nonspecific lines of defense, the skin and mucus membrane, phagocytes, natural killer cells, inflammation, and antimicrobial proteins

E. Lymphocytes

1. Lymphocytes are a type of white blood cells that provide specificity and diversity in protecting the body

2. The two main types of lymphocytes B lymphocytes (B cells) and T lymphocytes (T cells)

3. Antigens are a substance that prompts the generation of antibodies and can cause an immune response.

4. Antigens are from viruses, bacteria, fungi, protozoa, and parasites

5. Antigens signal an immune response by activating B cells to create antibodies

6. Antigen receptors on B cells are transmembrane version of antibody molecules

7. T cell receptors are antigen receptors on a T cell but unlike the antibodies the T cell receptor is never produced in a secreted form

F. Immune Response and Immunological Memory

1. The lymphocyte multiply and differentiate forming clones cells

2. The clone cells consist of one short lived cell the effector cell and one long lived cell the memory cell

3. The effector cell combats the antigen and the memory cell bears receptors specific for the antigen

4. Secondary response to the same antigen is much quicker than the first

G. The Body’s self Toleration

1. Lymphocytes like blood cells are created by pluripotent stem cells in the bone marrow

2. B cells mature in the marrow while T cells mature in the thymus

3. The bodies self toleration as the lymphocytes bearing receptors specific for native molecules are destroyed or are nonresponsive

4. Major histocompatibility complex (MHC) is a glycoprotein or protein attached with sugar

5. Class 1 MHC are located on all nucleated cells and present antigen fragments to cytotoxic T cells

6. Class 2 MHC are found on macrophages and B cells and present antigen fragments to helper T cells

7. Cytotoxic T cells have antigen receptors that bind to fragments of antigens

H. Immune Response

1. The immune system can respond in two ways humeral response or cell mediated response

2. Humeral response involves B cells and is based on the circulation of antibodies

3. The humeral response helps the body with viruses, bacteria, and other extracellular threats

4. Cell mediated response involves T cells and immunity against intracellular pathogens

5. The cell mediated response and T cells are active against bacteria, viruses, fungi, protozoa and parasites

I. Helper T Function in Both Humeral and Cell Meditated Immunity

1. Antigen presenting cells (APC) alert the immune system by way of the helper T cell

2. Cytokines are secreted by activated T cells

3. CD4 is a co-receptor that assists the T cell receptor to activate its T cell following an interaction with an antigen presenting cell

4. Suppressor T cells (T_S) is in charge of turning off the immune system as soon as the antigen has completely left the body

J. Cell Mediated Response, Cytotoxic T Cells Counter Intracellular Pathogens

1. Antigen activated cytotoxic T cells lymphocytes kill cancer cells as well as cells infected by viruses or other pathogens

2. Interaction between cytotoxic T cell and the antigen presenting cell is improved by the protein CD8

3. The cytotoxic T cell eliminates its target cell by releasing the protein perforin

4. Tumor cells carry distinct molecules that are not found on normal cells

5. Class 1 MHC send fragments of tumor antigen to cytotoxic T cells

K. B Cells Make Antibodies Against Extracellular Pathogens

1. Long lived memory B cells are provoked by the T dependent antigens

2. Other antigens such as polysaccharides and proteins act as T independent antigens

3. Antibody Structure and Function

a. Antigens that bring forth a humeral response typically are protein and polysaccharide surface component of various microbes

b. Antibodies interact with the small but accessible portion of the antigen known as the epitope

c. Immunoglobulins (Igs) are a group of globular serum proteins that are antibodies

d. The five most common types are Iga, IgD, IgE, IgG, and IgM

e. Each molecule contains four polypeptide chains two being heavy chains and the other two light chains

4. Antibody Mediated Disposal of Antigens

a. Antibodies and antigens bind forming antigen-antibody

b. The simplest of these is neutralization in which the antibody blocks the activity of the antigen

c. The antigen that is newly coated with the antibody are eliminated in a process called phagocytosis in a process call opsonization

d. Compliment fixation is the binding of active serum complement to an antigen-antibody pair

e. Lysis can be achieved through either the classical pathway or the alternative pathway

f. The classical pathway is triggered by antibodies bound to antigens

g. The alternative pathway is triggered by substance found in bacteria, yeast, viruses, protozoan and parasites

h. Membrane attack complex forms a pore in the bacterial membrane allowing ions and water to enter the cell ultimately causing it to lyse

L. Artificial and Natural Immunity

1. Active immunity is gained by recovering from a disease such as the chickenpox

2. Active immunity in this case is natural but it can be obtained artificially by immunization also called vaccination

3. In a vaccination inactive bacteria is injected to the body, the disease can not spread but the body still cans the active immunity from fighting the disease

4. Passive immunity is antibodies passed from one person to another

5. This is usually done between mother and baby through the placenta or through breast feeding

M. Blood Groups and Blood Transfusions

1. People type A blood have the A antigen which is completely harmless to the even though it is call an antigen

2. It is call an antigen because if type A blood was present in a person that was type B then it would be an antigen to that person

3. People with AB blood type can receive both A and B blood types there are known as the universal receivers

4. O blood type do not either antigens so they are considered the universal donors but they can only receive O blood in a transfusion

5. Blood groups antigens are polysaccharides and induce t independent response which do not have memory cells

6. Therefore every response is like a primary response so it generates IgM antibodies and not IgG

7. This is important because IgM does not travel through the placenta

8. Rh factor is able to produce IgG antibodies which will travel across the placenta

N. Tissue Grafts and Organ Transplants

1. Major histocompatibility complex (MHC) is responsible for rejecting tissue grafts and organ transplants

2. So to minimize this rejection it’s important to try to get a close match of the MHC

3. Siblings are usually the best choice for this match

4. Cyclosporine A and FK506 suppress the helper T cells without taking out the whole body’s defense improving the success of transplant

5. This limits the graft versus host reaction

O. Abnormal Immune Function Can Lead To Disease

1. Allergies

a. Allergies are extreme reactions or responses to environmental antigens called allergens

b. Anaphylactic shock is a life threatening allergic reaction

c. Anaphylactic shock occurs when an allergic response triggers a quick release from mast cells leading to sudden drop in blood pressure resulting in difficulty breathing

d. Anaphylactic shock can lead to death in a matter of minutes if left untreated.

2. Autoimmune Diseases

a. The immune system loses its tolerance for itself and fights against certain molecules of the body

b. An example of this is Lupus which attacks the body’s cells and tissue, resulting in inflammation and tissue damage

c. The cause of these diseases vary and there is still much unknown about them

3. Immunodeficiency Diseases

a. Is a state in which the immune system's ability to fight infectious disease is compromised or entirely absent

b. Some diseases require bone marrow transplants for long term survival

c. Some of these disease are inborn while other can be developed later on in life

P. AIDS

1. People with Acquired Immunodeficiency Syndrome (AIDS) are more susceptible to opportunistic diseases

2. These opportunistic diseases are cancers and infections that take advantage of immune systems that have collapsed

3. The retrovirus call Human Immunodeficiency Virus (HIV) is responsible for causing AIDS

4. HIV is the most lethal pathogen, AIDS mortality rate is near 100%

5. There are two major strains of the virus HIV-1 and HIV-2, HIV-1 being more common

6. Late in AIDS the immunity collapses with the loss of CD4 T cells

7. The time for HIV to turn into AIDS averages about 10 years

8. During this time the person exhibits hints of illness such as the swollen lymph nodes and occasional fever

Chapter 44

Controlling the Internal Environment

A. Regulation of Body Temperature

1. Thermoregulation is the maintenance of body temperature within a specific region that allows cells to function

B. Four Physical Processes that Account For Heat Gain and Loss

1. Conduction

a. The direct transfer of heat between the environment and body

b. An example would be sitting out in the hot sun and swimming in a cool pool

2. Convection

a. The transfer of heat by the movement of air or liquid past the surface of the body

b. An example is a fan on a hot day

3. Radiation

a. Emission of electromagnetic waves produced by all objects warmer than absolute zero

b. An example is the sun

4. Evaporation

a. The loss of heat from the surface of a liquid

b. An example would be sweating

C. Ectotherms and Endotherms

1. Ectotherms obtain their body heat by absorbing heat from the surrounding environment

2. Most amphibians, fish, and reptiles are ectotherms

3. Endotherms get most of their body heat from their metabolism

4. Mammals, birds, some fishes, and insects are endotherms

D. Thermoregulation

1. Both ectothermic and endothermic animals have to thermoregulate

2. Animals adjust the rate of heat exchange with their surroundings by evaporative cooling and behavior modifications

3. Some of these behavior changes include vasodilation, vasoconstriction, as well as countercurrent heat exchanger

4. Vasodilation is increasing the diameter of the superficial vessels near the body’s surface increasing blood flow and heat

5. Vasoconstriction is the opposite of vasodilation and decreases heat

6. Countercurrent heat exchange is the exchange of heat from arteries carrying blood away from the hart and veins carrying blood towards

7. Animals that live on land are constantly loosing water through evaporation this also cools the body

8. Many animals will relocate themselves to warm up or cool down

9. Endotherms can increase their metabolic rate to increase their body temperature

E. Most Animals Are Endothermic But Endothermy Is Widespread

1. Invertebrates

a. Nearly all invertebrates have very limited control over their body temperature

b. Some insects such as bees can contact their muscles to increase body temperature allowing them to fly during cold days

2. Amphibians and Reptiles

a. Amphibians and reptiles are for the most part ectothermic and have low metabolic rates

b. They produce very little heat themselves and are rapidly losing heat to evaporation

c. They are constantly seeking out warm places or shade if they get too warm

3. Fishes

a. The body temperature of fish is very close to the temperature of the water

b. Metabolic heat generated by swimming is lost to the surrounding water

c. The swimming muscles are a few degrees warmer than the tissue near the water

4. Mammals and Birds

a. Birds and mammals have a narrow range of temperature mammals ranges from 56^o-38^o C and for birds 40o-42o C

b. To maintain these temperatures their bodies need to balance their metabolic heat with heat gain or loss

c. Nonshivering thermogenesis is the process of heat production in organisms

5. Feedback Mechanism in Thermoregulation

a. Nerve cells that control thermoregulation are located in the hypothalamus

b. The hypothalamus contains a thermostat that reacts in both temperature increase and decrease

c. Some heat saving mechanisms such as vasoconstriction of superficial vessels and the erection of fur while stimulating shivering and nonshivering thermogenesis

d. Somebody cooling mechanisms include vasodilatation, sweating, and panting

6. Temperature Range Adjustments

a. Acclimatization is the process of an organism adjusting to change in temperature

b. An example of these changes in temperature would be summer to winter

c. Special molecules are induced to help the body deal with sever stress like temperature change

d. These molecules are called stress induced proteins which include the heat shock protein

7. Torpor

a. This is an alternative physiological state in which metabolic rate decreases and heat and respiratory systems slow down

b. Hibernation is the long term version of torpor

c. Estivation is similar to hibernation except the opposite instead of sleeping through the winter the animals sleeps through the summer

d. Torpor is not always long term for example the bat feed at night and go into torpor during the day

F. Water Balance and Waste Disposal

1. Transport Epithelium

a. Water balance and waste disposal are both dependent on transport epithelium

b. Some transport epithelium are exposed to outside environment while others face a series of channels that lead to the outside

2. Nitrogen Waste

a. Nitrogen waste from the breakdown of proteins and nucleic acids can be some of the most toxic byproducts of metabolism

b. Nitrogen waste product is ammonia which is a very toxic molecule

c. Some animals convert the ammonia into urine which takes energy while others dispose of it directly

3. Ammonia

a. Most of the aquatic animals dispose nitrogen waste as ammonia

b. Ammonia is dissolvable in water and easily passes through membranes

c. NH₄⁺ is the chemical formula for ammonia

4. Urea

a. Disposal of ammonia on land is not good so the animal converts it to urea

b. Converting ammonia to urea or urine takes energy

c. Some animals that live in water and land can switch methods of disposing there ammonia

5. Uric Acid

a. Snails, insects, birds, and reptiles excrete uric acid as their nitrogen waste

b. Uric acid is a thousand times less soluble in water than ammonia or urea

c. Uric acid allows these animals to dispose of their nitrogen waste with limited water loss

6. Cells Require A Balance Between Osmotic Gain And Loss of Water

a. Cells are not able to survive a net gain or loss of water

b. The cell will swell up and burst if there is too much

c. The cell will shrivel up and die if there is too little

d. Glucose and protein in the interstitial fluid help keep the balance

7. Osmoregulators and Osmoconformers

a. The body obtains most of its water through food and drinking

b. The body loses most of its water through urine and sweating

c. Osmoregulators is the active regulation of the osmotic pressure of bodily fluids to maintain the homeostasis of the body's water content

d. Osmoconformers do not actively exchange solutes with the environment, but keep their body fluids isotonic to the external

e. Stenohaline are animals that are unable to survive extensive changes to the external osmolarity most animals are Stenohaline

f. The animals that can survive are called euryhaline

g. Sharks have an osmolarity slightly higher than seawater because they retain urea. Marine bony fish lose water to their hyperomotic environment

h. Freshwater protists pump out excess water with contractile vacuoles, while freshwater animals excrete dilute urine

i. Salt loss is replaced by eating or by ion uptake by gills

j. Some animals are able to exist in a dormant state in dehydration in an adaptation called anhydrobiosis

k. Most land animals replenish their water supply by drinking and eating moist foods

G. Excretory System

1. Most Excretory Systems Produce Urine by Filtrating Derived From Body Fluids

a. To start urine production the blood is filtered so the membrane retains proteins and other large molecules in the body fluid. This filtered liquid is the filtrate

b. The capillaries than reabsorb glucose, slats, and amino acids, from the filtrate

c. Also the capillary secretes solutes that are removed from the animal’s body fluids and added to the filtrate

2. Diverse Excretory Systems Are Variations on a Tubular Theme

a. A protonephridium is a network of closed tubules lacking internal openings

b. Flatworms use the flame-bulb system where the extra cellular fluid is filtered into the protonephridia

c. Tubules excrete a dilute fluid which is also used for osmoregulation.

d. The metanephridium, system of the earthworm has internal openings that collect body fluids in each segment

e. Reabsorption and secretation are done as the urine exits through the nephridiopores

f. Malipighain Tubules are used in insects which are dead end tubes that contain salt, water, and nitrogenous wastes

g. It adds this to the food, where nutrients are reabsorbed and feces urine is the leftovers

3. Nephrons and Associated Blood Vessels

a. They are the functional units of the mammalian kidneys

b. The body has two kidneys, blood enters through the renal artery and leaves through the renal vein

c. Urine exits the kidney through the ureter where it goes to the bladder

d. The kidney includes the inner renal medulla and the outer renal cortex. In both regions tubules called nephrons are the functional unit of the kidney

e. They consist of a long tubule and a ball of capillaries called the glomerules, and the blind end of the tubule forms a cup shaped surrounding the glomerulus called Bowman’s capsule.

f. The filtration of the blood occurs at Bowman’s capsule in the Glomerulus, where podocytes filter the blood allowing small particles to pass even salt, glucose, and vitamins

g. The filtrate goes through the proximal tubule, the loop of Henle, and the distal tubule which empties into the collecting duct which empties into the renal pelvis.

h. Juxtamedullary nephrons have a full loop of Henle as the cortical nephrons do not

i. The nephron and the collect duct are lined by a transport epithelium where secretions and reabsorption occur

j. Blood vessels go to afferent arteriole glomerulus efferent arteriole, peritubular capillaries, vasa rectum, branch of renal vein

1. 1. From Blood Filtrate To Urine

a. Secretion and reabsorption by transport epithelium of the proximal tubule altars the volume and composition of filtrate

b. The transport epithelium helps control the pH in the body by controlling the secretion of hydrogen atoms

c. One of the most important function of the proximal tubule is to reabsorb NaCl (salt) as well as water

d. Reabsorption continues on into the descending limb of the loop of Henel

e. As this reabsorption of water takes place the NaCl concentration increases

f. In the ascending limb of the loop of Henel the diffuses out into the interstitial fluid

g. The distal tubule plays an important role in controlling the concentration of K⁺ and NaCl in the body fluids

1. 1. The Mammalian Kidney’s Ability To Conserve Water

a. The mammalian kidney’s ability to conserve water is key to the terrestrial life style

b. The excretion of salt and water from the urea allows the kidney to produce urine

1. 1. Nervous System and Hormone feedback Circuits Regulate Kidney Function

a. ADH or anti-diuretic hormone is an important osmoregulation

b. This hormone in the kidney allows water to be more reabsorbed

c. During excessive water loss such as diarrhea or sweating an increases in ADH is secreted to compensate

d. Specialized tissue called juxtaglomerular apparatus or JGA is located in the afferent arteriole supplies blood to the glomerulus

e. When blod pressure drops the enzyme rennin initiates chemical reaction to convert a plasma protein called angioteninogen to a peptide called angiotensin II

f. RASS is the renin-angiotensi-aldosterone system is part of a complex feedback circuit that helps homeostasis

g. ANF is the atrial natriuretic factor opposes the RAAS and helps in the response of increased blood pressure

1. 1. Adaptations of The Vertebrate Kidney Have Evolved in Different Habitats

a. Bird have kidneys with juxtamedullary nephrons specializes in conserving water

b. Reptiles have cortical nephrons that produce urine that is isoosmotic to body fluids

c. Fresh water fish have to excrete excess water because it is hyperosmotic to its surroundings

d. Amphibians are like fresh water fish while in the water and on land they reabsorb water across the epithelium of the urinary bladder

e. Seawater fish are hypoosmotic to their surroundings so these fish excrete very little urine

1. 1. Interacting Regulatory Systems Maintain Homeostasis

a. Homeostasis depends on the interaction of numerous regulatory systems and organ systems

b. The liver, feedback circuits, nervous system and hormones are all examples of systems that help maintain homeostasis

Chapter 45

Chemical Signals in Animals

A. An Introduction To Regulatory Systems

a. Hormone secreting cells are the endocrine system, as the hormone-secreting organs are called endocrine glands

1. The Endocrine System Versus The Nervous System

a. Both systems are structurally, chemically, and functionally related

b. Many endocrine organs and tissue contain specialized nerved cells called neurosecretory cells that secrete hormones

c. Feedback is another common feature of both systems

2. Invertebrate Regulatory Systems Clearly Shows Endocrine and Nervous system Interactions

a. In more complex invertebrates the endocrine and nervous systems are generally integrated in the control of reproduction and development

b. Crustaceans have hormones for growth, reproduction, water balance, movement of pigments in the integument and the eyes, and regulation of metabolism

c. In insects and crustaceans molting is triggered by a hormone called ecdysone

d. It is secreted by the to prothroacic glands, and also helps the development of insects

e. Brain Hormone or BH stimulates the prothroacic gland to release ecdysone

f. Juvenile Hormone or JH balance the BH and the ecdysone

B. Chemical Signals and Their Modes of Action

1. A Variety of Local Regulators Affect Neighboring Target Cells

a. Nitric oxide (NO) functions as a neurotransmitter if secreted by a neuron

b. If NO is secreted by white blood cells it kills cancer cells and bacteria

c. If NO is secreted by endothelial cells the smooth muscles nearby relax

d. Growth factors are peptides and proteins that function as local regulators

e. They must be present in the extracellular environment for many types of cells to grow, divide, and develop normally

f. Prostaglandins (PGs) stimulate smooth muscles in the wall of the uterus to help pass on the sperm to the egg

g. PGs also help in contractions during birth, and induce fever and inflammation

h. PGE which is prostaglandin E causes muscles to relax, and promotes oxygenation of the blood

i. PGF prostaglandin F signals the muscles to contract, which constricts the vessels and reduces blood flow through the lungs

2. Chemical Signals Bind to Specific Receptor Proteins

a. Chemical signals can trigger changes in target cells differently depending on the type of receptor

b. The type of receptor cell and whether they enter the cells or attach to the surface of proteins

3. Most Chemical Signals Bind to Plasma-Membrane Proteins

a. This initiates single transduction pathways

b. Most chemical signals are unable to pass through the cell membrane and bind to specific receptors on the plasma membrane

c. These signals trigger changes in target cells through signal transduction pathways

4. Steroid Hormones, Thyroid Hormones and Some Regulators Enter Target Cells and Bind With Intracellular Receptors

a. Chemical signals that actually enter target cells bind to specific protein receptors in the cytoplasm

b. Hormone receptor complexes then enter the nucleus, bind to certain sites on DNA and effect changes in gene expression

C. The Vertebrate Endocrine System

a. Tropic hormones have other endocrine glands as their targets

1. The Hypothalamus and Pituitary Integrate Many Functions of The Vertebrate Endocrine System

a. Neurosecretory cells of the hypothalamus integrate endocrine and neural functions by influencing the pituitary gland

b. The posterior pituitary is an extension of the brain that stores and releases two hormones oxytocin and antidiuretic hormone (ADH)

c. Oxytocin acts on muscles of the uterus to induce contractions of the uterine muscles during childbirth and causes the mammary glands to eject milk during nursing

d. ADH acts on the kidneys increasing water retention and thus decreasing urine volume

e. The anterior pituitary produces an array of hormones including thyroid stimulating hormone (TSH), follicle stimulating hormone (FSH), luteinizing hormone (LH), growth hormone (GH) and others

f. ADH is part of a feedback that regualtes the osmolarity of the blood

g. Blood osmolarity is monitored by a group of nerve cells that function as osmoreceptors in the hypothalamus

h. When the osmolarity of the plasma increases, these cells shrink slightly and transmit nerve impulses to certain neurosecretory cells in the hypothalamus

i. These cells then release ADH, and when it reaches the kidneys it binds to receptors of the surface of the cells lining the collecting ducts, and increases the water permeability, also the osmoregulators stimulate thirst

j. adrenocorticotropic hormone or ACTH controls the adrenal cortex

k. follicle-stimulating hormone or FSH and luteninizing hormone control reproduction by acting on the gonads

l. Growth hormones are proteins consisting of almost 200 amino acids and affect a wide variety of target tissues. It promotes directly and stimulates the production of growth factors

m. Endorphins in the brain are natural opiates and reduce pain

2. The Pineal Gland is Involved in Biorhythms

a. This gland Secretes Melatonin which influences skin pigmentation, biological rhythms and reproduction in many vertebrates

3. Thyroid Hormones Function in the Development, Bioenergetics and Homeostasis

a. The thyroid gland consist of two lobes located on the ventricle surface of the trachea

b. Tri-iodothyronine (T₃) and thyroxine (T₄) contain three and four iodine atoms respectively, both stimulate metabolism and influence development

c. Calcitonin secreted by the thyroid lowers calcium levels in the blood

4. Parathyroid Hormone and Calsitonin Balance Blood Calcium

a. There are four parathyroid glands located in the thyroid

b. They secrete parathyroid hormone (PTH) which raises calcium levels

5. Endocrine Tissue of the Pancrease Secrete Insulin and Glucagon, Antagonistic Hormones That Regulated Blood Glucose

a. Insulin lowers the blood glucose level as glucagon raises it also Insulin signals all the cells of the body accept the brain to take up glucose from the blood

b. Glucagon starts working as soon as excess glucose is cleared from the blood, glucagon signals liver cells to increase glycogen hydrolysis, convert amino acids and fatty acids to glucose, and start slowly releasing glucose back into the circulation

c. Type I diabetes mellitus is an autoimmune disorder where the immune system attacks the pancreas

d. Type II diabetes mellitus is a deficiency of insulin or reduced responsiveness in target cells due to some change in insulin receptors

6. The Adrenal Medulla and The Adrenal Cortex Help The Body Manage Stress

a. The adrenal glands are adjacent to the kidneys

b. The adrenal gland is made up of two glands the adrenal cortex outer part and the adrenal medulla inner or central part

c. Increased heart rate or goose bumps are part of the fight-or-flight reaction

d. The adrenal medulla secretes epinephrine also known as adrenaline and norepinephrine to stimulate the fight or flight response

e. These two hormones are members of the catecholamines which are synthesized from amino acid tyrosine

f. The adrenal cortex release corticosteroids, glucocorticoids, mineralocorticoids

g. Corticosteroids include sex hormones, glucocorticoids influence metabolism and immune system, mineralocorticoids affect water and salt balance

7. Gonadal Steroids Regulate Growth, Development, Reproductive, Cycles and Sexual Behavior

a. The gonads produce and secretes threes major steroid hormones, androgens, estrogens, and progestin

b. Androgens which includes testosterone stimulates the development of the male reproductive system as well as developing the fetus into male rather than female

c. Estrogen including estradiol helps in maintenance as well as develop of female secondary sex characteristics

d. Progestin is involved in preparing and maintaining the uterus along with growth and support of the fetus

Chapter 46

Animal Reproduction

A. Overview of Animal Reproduction

1. Both Asexual and Sexual Reproduction Occur in The Animal Kingdom

a. Asexual reproduction is reproduction with genes coming from one parent without the fusion of sperm and egg

b. Sexual reproduction is the fusion of haploid gametes to form a zygote

c. The ovum is the female gamete, and the spermatozoon is the male gamete

d. Greatest advantage of sexual reproduction is the enhancement in genetic variability

2. Asexual Reproduction

a. The different mechanisms of asexual reproduction include, fission, budding, fragmentation and regeneration

b. Fission is the separation of one individual into two or more individual

c. Budding is the new individual grows off of the parent

d. Fragmentation is the breaking of body parts into several piece that develop into adults this must be accompanied by regeneration or regrowth of lost body parts

3. Reproductive Cycles and Patterns Vary Extensively Among Animals

a. Most animals reproduce seasonal cycles which is somewhat controlled by the pineal gland

b. Some animals are able to reproduce both ways. These animals let one egg be fertilized and the other is developed without being fertilized as a haploid

c. This process is called parthenogenesis this also is used by bees, wasps, and ants that use parthenogenesis for males and sexual reproduction for females

d. Some animal species reproduce from a more complex parthenogenesis where the off spring is a diploid

e. For burrowing animals and parasites sexual reproduction is a problem but hermaphroditism, which is the presence of male and female reproductive systems is able to solve this as each member is a potential mate

f. Some animals are sequential hermaphroditism, where individuals reverse their sex during a lifetime. This can be protogynous female first or protandrous male first

B. Mechanism of Sexual Reproduction

1. Internal and External fertilization

a. Fertilization is the union of sperm and egg

b. External fertilization is eggs are shed by the female and fertilized by the male

c. Internal fertilization is the male deposits sperm near the females reproductive tract and the fertilization occurs within

d. Species with external fertilization usually live in a warm moist environment and produce many eggs

e. Pheromones are chemical signals released by an organism that influences the behavior of another of the same species

2. Species With Internal Fertilization

a. They usually produce less zygotes and require more parental protection

b. In early development many offspring still need parental care to survive

3. Complex Reproductive Systems Have Evolved in Many Animal Phyla

a. The least complicated systems do not have distinct gonads or organs that produce gametes in most animals

b. The least complex system is of the polychaete worms which have separate sexes but not gonads

c. When the gametes mature they are released from the body wall and fill the coelom

d. Most insects have separate sexes with sperm developed, in the testes, ejaculated by a penis into a vagina with two ovaries

e. One characteristic is a spermatheca which is a sac where females can hold sperm for a year.

f. The cloaca is an opening to the outside in nonmammalian vertebrates, which is for the digestive, excretory, and reproductive systems

C. Mammalian Reproduction

1. The Male Reproductive Anatomy

a. The external reproductive structures of the male are the scrotum and penis

b. The male gonads or testes consist of highly coiled tubes surrounded by several layers of connective tissue

c. These tubes are called the seminiferous tubules and is where sperm is formed

d. Leydig cells are scattered between the seminiferous tubules and produce testosterone and other androgen which are male sex hormones

e. The scrotum is a fold of the body wall and is 2^oC cooler than the abdominal cavity

f. From the seminiferous tubules the sperm passes into the coiled tubules of the epididymis, here is where the sperm gains the ability to fertilize

g. During ejaculation the sperm is propelled from the epididymis to the vas deferens and to the ejaculatory ducts which open up into the urethra

h. The urethra drains both the excretory system and the reproductive system, it runs through the penis to the tip

i. The semen which is the liquid ejaculated is made by secretion by the seminal vesicle prostate and bulbourethral gland

j. The seminal vesicles give 60 percent of the semen volume and give the energy to the sperm, a coagulating enzyme, ascorbic acid, and prostaglandins

k. The prostate gland is large and its fluid is put directly into the urethra. The fluid contains anticoagulant enzymes, and a sperm nutrient citrate

l. The bulbourethral glands are just below the prostrate and the clear mucus neutralizes the acidic urine leftovers

m. Semen first coagulates to go up the uterine contractions then liquidizes to swim the rest of the female tract. The semen is also alkaline to counter act the acidity of the vagina

n. The penis has spongy erectile tissue when aroused the tissue is filled with blood and the veins cut off so the penis engorges

o. Rodents, raccoons, walruses, and several other mammals have a baculum which is a bone that contained in, and helps stiffen, the penis

p. Impotence is the inability to erect

q. The shaft of the penis is covered by thick skin, but the head or glans penis has a thinner covering for sensation

r. The foreskin or prepuce is the fold of skin covering the human glans, and can be taken off in a circumcision

2. The Reproductive Anatomy of the Human Female

a. The female gonads are the ovaries and they are located in the abdominal cavity, the ovary contains many follicles

b. The follicles consist of egg cells which are surrounded by follicle cells which nourish and protect the developing egg

c. The process of the egg cell being expelled from the follicle is called ovulation

d. The corpus luteum secretes estrogen and progestin to maintain the uterine lining during pregnancy, when the egg does not become fertilized the corpus luteum dissolves

e. The oviduct or fallopian tube uses cilia on the inner epithelium to get the egg to the womb, or uterus by moving body fluid

f. The uterus is thick and muscular and expands during pregnancy

g. The neck of the uterus is the cervix which opens to the vagina

h. The hymen is a vascular membrane the covers the vagina usually from birth till sexual intercourse or vigorous exercise

i. The vagina anis separated from the urethral opening by the vestibule, and is bordered by the labia minora, and labia majora

j. The clitoris is a short shaft supporting rounded glans, or head, covered by a small hood of skin, the prepuce during sexual arousal, the clitoris, vagina, and labiaminora all engorge with blood and enlarge

k. In intercourse Bartholin’s glands secrete mucus to lubricate the vagina

l. Mammary glands function normally in women only and have small sacs of epithelial tissue which secrete milk, which drains into a series of ducts opening at the nipple

3. The Human Sexual Response

a. Vasocongestion occurs in both sexes and is the filling of tissue with blood by increased blood flow through the arteries of that tissue and myotonia or increased muscle tension

b. The sexual response cycle can be divided into four phases excitement, plateau, orgasm, resolution

c. Excitement occurs in the erection of the penis and clitoris, enlargement of the testes, labia and breasts, and vaginal lubrication,

d. The plateau phase increases the heart rate as well as breathing increase not because of physical exertion but because of the autonomic nervous system

e. Orgasm is the rhythmic involuntary contraction of both reproductive structures

f. Male orgasm is emission or filling the urethra with semen. Expulsion which is when the urethra contracts and the semen is expelled, female orgasm is the contraction of the outer uterus and vagina.

g. The resolution cycle reverse the responses of the other three phases bringing everything back to normal

4. Spermatogenesis and Oogenesis Both Involve Meiosis but Differ in Three Ways

a. Spermatogenesis is the production of mature sperm cells and is a continuous process

b. The sperm cell consists of a haploid nucleus and tipped with acrosome which contains enzymes that help the sperm penetrate the egg. Behind the head, the mitochondrion lays which gives the ATP the tail needs to move

c. Oogenesis is the development of ova, or mature unfertilized egg cells. Before puberty the egg cells enlarge, and the follicles around it to grow

d. Beginning at puberty, FSH periodically stimulates a follicle to grow and induces its primary oocyte to complete the first meiotic division

e. The secondary oocyte is released then undergoes the second meiotic division right away

f. There are 3 differences between the processes

g. ovum that develops is the only one of the four cells created that is a gamete the others are smaller polar bodies, and degenerate

h. Sperm create four sperm cells from each diploid. Sperm cells develop and continue to divide by mitosis throughout the male’s life

i. In females the number of eggs is determined at birth, Oogenesis also has a long resting period as spermatogenesis is uninterrupted.

5. A Complex Interplay of Hormones Regulates Reproduction

a. Androgens in the testes develop the primary and secondary sex characteristics in the male

b. Androgen secretion and sperm production are both controlled by hypothalamic and pituitary hormones

c. Female hormones are secreted in a rhythmic fashion reflected in the menstrual or estrous cycle, They both prepare for implantation of the zygote

d. The estrous cycle is also more affected by season and climate and creates more behavioral changes

e. The menstrual cycle starts with the menstrual flow phase when the menstrual bleeding occurs, the thin remaining endometrium than starts to regenerate and thicken during the proliferative phase

f. Then ovulation, then the secretory phase, where the endometrium thickens and develops glands the secrete glycogen rich fluid

g. The cycle repeats if not embryo has implanted.

h. The ovarian cycle parallels the menstrual cycle and begins with the follicle phase where several egg cells enlarge and the coat of the follicle cell becomes multilayered

i. Of the follicles that have started to grow usually only one continues to grow and develop and the rest disintegrate

j. The mature follicle develops an internal fluid-filled cavity and grows, creating a bulge near the surface of the ovary

k. Hormones coordinate the menstrual and ovarian cycles in such a way that follicle growth and ovulation are synchronized with the preparation of the uterine lining

l. The five hormones responsible are gonadotropin-releasing hormone, FSH, LH, estrogen, and progesterone

m. The developing follicles secrete estrogen, and when the estrogen raises steeply the LH and PSH rise radically causing ovulation

n. As the corpus luteum excretes estrogens and progesterone the LH and PSH are controlled and decreased. As the corpus luteum disintegrates the estrogen and progesterone levels decrease and FSH is able to allow follicle development

o. Estrogen is also responsible for the secondary sex characteristics of the female, fat in the breasts and hips, increased water retention, affect calcium metabolism, fuel breast development, and mediate female sexual behavior

p. Menopause is the cessation of ovulation and menstruation. It is caused by the ovaries lose of responsiveness to gonadotropins from the pituitary, and a decline in production of estrogens by the ovary.

1. 1. Embryonic and Fetal Development

a. Human pregnancy can be divided into three trimesters about 3 months each

b. Organogenesis is completed in the first 8 weeks the development of body organs, and as the rudimentary organs form the embryo becomes a fetus, this is where defects occur may occur

c. The female’s reproductive system is affected by human chorionic gonadotropin (HCG)

d. During the second trimester the fetus grows and becomes more active. The hormone levels stabilize as HCG declines, the corpus luteum deteriorates, and the placenta secretes its own progesterone.

e. The third trimester also is marked by rapid growth, the contractions are started by oxytocin, which stimulates the placenta to secrete prostaglandins, which enhance the contractions

f. The ability of a female to accept foreign tissue in her body for 9 months is unknown although there are several theories

g. Contraception is the deliberate prevention of fertilization or pregnancy

h. Barrier methods are ways from blocking sperm from meeting egg. This is condoms

i. Intrauterine devices are small devices in the uterine cavity that prevent implantation of the blastocyst in the uterus

j. Withdraw or removal of the penis before ejaculation is not reliable

k. The most effective birth control is abstinence

l. The permanent prevention of gamete release is tubal ligation in women involving tying off the oviducts to prevent eggs from traveling to the uterus

m. Vasectomy is the cutting of each vas deferens to prevent sperm form entering the urethra

1. 1. Modern Technology Offers Solution for Some Reproductive Problems

a. These methods include ultrasound imaging, amniocentesis, and chronic villus sampling

b. In vitro fertilization was developed for women whose oviducts are blocked

Chapter 47

Animal Development

A. The Stages of Early Embryonic Development

1. From Egg to Organism

a. One early theory of embryo development was preformation which was that the embryo was already formed and just got bigger

b. The competing theory of embryonic development was epigenisis proposed by Aristotle which was the form of an animal emerges gradually from a relatively formless egg

c. This became the accepted theory

2. Fertilization Activates the Egg and Brings Together the Nuclei of Sperm and Egg

a. Fertilization restates diploidy and activates the egg to begin a chain of metabolic reactions that trigger embryonic development

b. The sea urchins eggs are fertilized externally, the tip of the sperm called the acrosome discharges its contents by exocytosis to penetrate the jelly coat of the egg

c. The acrosomal reaction releases hydrolytic enzymes that enable structure called the acrosomal process to penetrate the egg

d. The tip of the acrosomal processes coated with a protein that adheres to receptors of the plasma membrane of the egg

e. With this fusion a neuron-like electrical response is elicited by the plasma membrane, called membrane depolarization, which opens up the ion channels for more sodium ions into the egg

f. The fast block to polyspermy prevent more than one sperm from entering the egg

g. After the fusion of sperm and egg the cortical reaction occurs. They are a series of changes in the cortex of the egg cytoplasm

h. The cortical granules then fuse with the plasma membrane and release their contents into the perivitelline space between the plasma membrane and the vitelline layer

i. Enzymes push the vitelline layer away from the membrane and an osmotic gradient is created from mucopolysaccharides, which swells up the perivitelline space

j. Other enzymes harden it, making it the fertilization membrane which is the protection of the egg from sperm cells in the long run, and is also called slow block to polyspermy

k. There are many differences between mammals and sea urchins

l. One is that mammalian females secrete the molecules of capacitating, which alters the surface of sperm cells and increases the motility of sperm

m. The sperm must migrate through the follicle cells before it reaches the extracellular matrix of the egg, the zona pellucida

n. The zona pellucida is made of three different glycoproteins forming a three dimensional network, and function as the sperm receptor

o. Another difference is the cortical reaction which uses granules in the cortex of the egg which releases their contents to the outside of the cell in exocytosis,

p. Enzymes released form the cortical granules catalyze alterations of the zona pellucida, to be the slow block to polyspermy

3. Cleavage Partitions the Zygote Into Many Smaller Cells

a. Fertilization is followed by three successive stages the build the animal’s body, the first is called cleavage

b. Cleavage is succession of rapid cell divisions that follow fertilization

c. During cleavage the cells undergo S (DNA synthesis) and M (mitosis) phases

d. Cleavage partitions the cytoplasm of the large cell, the zygote, into many smaller cells called blastomers each having its own nucleus

e. The yolk are the nutrients stored in the egg

f. The vegetal pole of the egg contains the highly concentrated egg as the animal pole does not and is where the head of the embryo will form

g. Animals with yolk the cells of the animal pole tend to be different sizes

h. As cleavage continues, it produces a solid ball of cells, the morula and a fluid filled cavity called the blastocoel. This hollow ball stage is the blastula

i. Meroblastic cleavage is the incomplete division of a yolk-rich egg, holoblastic cleavage is the complete division having little yolk

1. 1. Gastrulating Rearranges the Blastula to Form Three-Layered Embryo with a Primitive Gut

a. During gastrulation the cells move to different locations to make a three layered embryo called the gastrula

b. These layers are the ectoderm, endoderm, and mesoderm

c. Ectoderm is nervous system, and skin

d. Endoderm is inner most lining of our digestive tract and associated organs

e. Mesoderm is the other tissue and organs such as kidney, heart, muscles, and the dermis

f. In the sea urchin the blastula consists of a single layer of cells, gastrulation begins at the vegetal pole where cells from the blastula wall enter the blastocoel as migratory cells called mesenchyme cells

g. The remaining cells flatten to form a vegetal plate that buckles inward, in invagination

h. The vegetal plate then rearranges its cells which deepen the invagination into the archentron, or primitive gut

i. The open end of the archenteron will become the anus and is called the blastopore

1. 1. Organogenesis

a. Three germ layers develop into the rudiments of organs during the process organogenesis

b. The organ the begins to take shape first in frogs and other chordates are the neural tube and notochord

c. The notochord is formed from dorsal mesoderm that condenses just above the archenteron

d. The neural tube will become the central nervous system

e. Condensation also occurs in strips of mesoderm lateral to the notochord, which separate into blocks called somites

f. These somites give rise to the vertebrae of the backbone, and the muscles associated with the axial skeleton

g. The mesoderm splits into two layers that form the lining of the body cavity or the coelom

h. The neural crest which is unique to vertebrate embryo develops along the border where the neural tube pinches off from the ectoderm

i. Cells of the neural crest migrate to various parts of the embryo forming pigment cells of the skin, some of the bones and muscles of the skull, the teeth, the medulla of the adrenal glands, and peripheral components of the nervous system

1. 1. Amniotic Embryos Develop in a Fluid Filled Sac Within a Shell or Uterus

a. All vertebrate embryos require and aqueous environment for development

b. Within the shell or uterus, the embryos of birds, reptiles, and mammals are surrounded by fluid within a sac formed by a membrane called the amnion, and these vertebrates are called amniotes

c. In birds the early cleavage division produce cap cells called blastodisc, the blastomeres create high and low level epiblast and hypoblast

d. Gastrulation cells from the outside of the blostodisc move inward toward the yolk creating a grove called the primitive streak

e. All the cells that will form the embryo come from the epiblast, some of the epiblast cells pass through the primitive steak and move into the blastocoels

f. As the embryo has three germ layers, the borders of the embryonic disc fold downward and come together, pinching the embryo into a three-layered tube joined at midbody to the yolk

g. The tissue layers not part of the embryo develop into four extraembryonic membranes that support further embryonic development within the egg

h. They are the yolk sac, the amnion, the chorion, and the allantois

i. During cleavage the cells are split with no orientation, equally, and in longer time than other animals, the cells than compact at the eight-cell stage by proteins called cadherins

j. In seven days after fertilization the embryo has 100 cells arranged around a central cavity. This is called the blastocyst

k. At one end of the embryo a cluster of cells called the inner cell mass will be the embryo proper as the outer epithelium is the trophoblast wand will be the fetal portion of the placenta

l. The extraembryonic supports further development of the embryo in the egg, the chorion develops from the trophoblast, and surrounds the embryo and the other extraembryonic membranes

m. Amnion starts as a dome above the proliferating epiblast then encloses the embryo in the fluid-filled amniotic cavity

1. The Cellular and Molecular Basis of Morphogenesis and Differentiation in Animals
   1. Morphogenesis in animals involves specific changes in cell shape, position, and adhesion

a. Cytoskeleton rearrangements are responsible for changes in both shape and position of cells

b. Cells crawl within the embryo by using the cytoskeleton fibers to extend and retract cellular protrusions

c. Cell crawling is also involved in a type of morphogenetic movement called convergent extension

d. Cell adhesion molecules on cell surfaces are also important for cell migration and for holding cells together in tissue. One important class of these is cadherins, which need calcium ions for proper function and are particularly important in the formation of the frog blastula

1. 1. Fate Mapping Can Reveal Cell Genealogies in Chordate Embryos

a. Fate maps are techniques that determine which parts of the embryo give rise to what parts of the embryo and they were essential in discovering the three germ layers

1. 1. The Eggs of Most Vertebrates Have Cytoplasmic Determinants That Help Establish the Body Axes and differences Among Cells of the Early Embryo

a. Establishing the basic body plan is a first step in morphogenesis and is prerequisite to the development of tissues and organs

b. The basic polarities are not determined until after cleavage in humans and mammals

c. As development goes along cells may have the ability to give rise to different types of cells, but not the potency for another individual

1. 1. Inductive Signals Drive differentiation and Pattern Formation in Vertebrates

a. Cells in developing embryo receive and interpreted positional information that varies with location

b. Inductive signals play a vital role in pattern formation which is the development of the animals spatial organization, the arrangement of organs and tissue in their characteristics place in three dimensional space

c. Positional information control the pattern formation

d. Apical ectodermal ridge (AER) is a thickened are of ectoderm at the tip of the bud , the AER is required for the growth of the limb

e. Zone of Polarizing Activity (ZPA) is another major limb bud organizer like AER and is necessary for anterior-posterior axis of the limb

f. Before the hinds become forelimb or hindlimb signals set up patterns of gene expression to choose, and cause the limbs to react differently to same positional cues

g. A hierarchy of gene activations eventually affects the expression of homeobox-containing genes in cells of developing limb. These genes are involved in specify the identity of various regions of the limbs as well as of the body as a whole

Chapter 48

Nervous System

A. An Overview of the Nervous System

1. Three Overlapping Functions of Sensory Input Integration, and Motor Output

a. Sensory input is the conduction of signals from sensory receptors such as light detecting cells in the eyes

b. Integration is the process by which the information from the environmental stimulation of the sensory receptors is interpreted and the appropriate response is decided, this is carried out by the central nervous system (CNS)

c. Motor output is the conduction of signals from the CNS to the effector cells , muscle cells or carry out the body’s responses to stimuli

d. The central nervous system and the rest of the body are collectively call the peripheral nervous system (PNS)

2. The Nervous System is Composed of Neurons and Supporting Cells

a. Neurons are the functional unit of the nervous system and are specialized for transmitting signals, it has a relatively large cell body

b. Dendrites convey signals from their tips to the rest of the neuron, axons conduct messages toward the tips

c. Myelin sheath is an insulating layer that encloses the axon

d. Schwann cells form myelin sheaths in the PNS and oligodendrocytes form myelin sheaths in the CNS

e. Synaptic terminals relay signals by releasing chemical messengers called neurotransmitters

f. Synapse is the site of contact between the synaptic terminal and the neurotransmitters

g. Sensory neurons communicate information, interneurons integrate sensory input and motor output

h. The third class of nerve cellsis the motor neuron which convey impulses from the CNS to the effector cells

i. A ganglion is a group of nerve cell bodies, in the brain it is called nuclei

j. Blood brain barrier restricts the passage of most substances from entering the brain

B. The Nature of Neural Signals

1. Membrane Potential Arise From Differences in Ion Concentration Between a Cell’s Contents and the Extracellular Fluid

a. The membrane potential of a nontransmitting neuron is due to the unequal distribution of ions, in particular sodium and potassium

b. The cytoplasm is more negatively charged than the extracellular fluid

c. Membrane potential is maintained by differential ion permeabilities and the sodium-potassium pump

2. An Action Potential is an All or None Change in the Membrane Potential

a. Neurons and muscle cells have the ability to change the membrane potential, and are called excitable cells. The resting state is resting state of an excitable cell

b. Neurons have special ion channels, called gated ion channels that allow the cell to change its membrane potential in response to stimuli the cell receives

c. The stimuli could trigger a hyperpolarization which is an increase in the electrical gradient across the membrane, or a depolarization which is a reduction in the electrical gradient

d. Voltage changes produced by stimulation of this type are called graded potentials, because the magnitude of change depends on the strength of the stimulus

e. In an excitable cell the response to a depolarizing stimulus is grades with stimulus intensity only up to a particular level of depolarization is called threshold potential

f. If the depolarization reaches the threshold potential the type of response is call action potential

g. The action potential is not dependent on the magnitude of the strength of the stimulus. It becomes rapidly more positive with respect to the outside then is followed by a steep depolarizing phase

h. A refractory period follows the action potential which is the time the inactivation gate can open, and it sets the limit on the maximum rate at which action potentials can be generated

3. Action Potentials Travel Along an Axon Because They Are Self-Propagating

a. Once the action potential is initiated in the axon a wave of depolarization propagates a series of action potentials to the end of the axon

b. The diameter of the axon controls the rate of transmission of nerve impulses

4. Chemical or electrical Communication Between Cells Occurs at Synapses

a. The transmitting cell is called the presynaptic cell and the receiving cell is called the postsynaptic cell, the two types of synapses are electrical and chemical

b. In electrical synapses the cells are connected by gap junctions, intercellular channels allow the local ion currents of an action potential to flow between neurons

c. This make it possible for impulses to travel from neuron to neuron without delay and with no loss of signal strength

d. At a chemical synapses, a narrow gap, or synaptic cleft, separates the presynaptic cell from the postsynaptic cell

e. When an action potential arrives at the synaptic terminal it depolarizes the presynaptic membrane, , the neuron secretes neurotransmitter molecules into the synapses

f. As the molecules diffuse across the cleft the bind to the receptors of ion channels in the postsynaptic membrane, cause in the receptors to open their ion channel

5. Neutral Integration Occurs at the Cellular Level

a. A single neuron may receive information from numerous neighboring neurons through thousands of synapses some of them excretory and some inhibitory,

b. Excretory and inhibitory have the opposite effect in the postsynaptic cell

c. Excretory postsynaptic Potential of EPSP is when the electrical charge causes the binding of a neurotransmitter to the receptor

d. Inhibitory postsynaptic potential IPSP is the voltage change associated with chemical signing at the inhibitory synapses

e. The additive effect of postsynaptic potentials is called summation

6. The Same Neurotransmitter Can Produce Different Effects on Different Types of Cells

a. Acetylcholine is one of the most common neurotransmitters, it can be inhibitory or excitatory depending on the receptor

b. Biogenic amines are neurotransmitters derived from amino acids

c. GABA or Gamma aminobutyric acid, glycine, glutamate and aspartate are four amino acids known to functions as CNS transmitters

d. Neuropeptides are short chains of amino acids that serve as neurotransmitters

e. The neuropeptide called substance P is involved in the perception of pain

f. Endorphins decrease the perception of pain

C. Organization Nervous Systems

1. Nervous system Organization Tend to Correlate With Body Symmetry

a. Invertebrate nervous systems range from the diffuse nerve net of many cnidarians to highly centralized and complex systems of cephalopods

b. A nerve net is a basic system of nerves the branch throughout the body

c. A nerve cord is a thick bundle of nerves extending from the brain

2. Vertebrate Nervous Systems are Highly Centralized and Cephalized

a. In all vertebrates the brain and spinal cord make up the CNS

b. The brain has the integrative power that is responsible for the complex behavior characteristics of vertebrates

c. The spinal cord integrates simple responses to certain kinds of stimuli and transports information to and from the brain

d. The CNS contains fluid-filled spaces that are continuous in the central canal of the spinal cord and are ventricles in the brain

e. The fluid is cerebrospinal fluid, which is formed in the brain by filtration of the blood. The fluid transports nutrients, hormones, and white blood cells across the blood-brain barrier to different parts of the brain, it also is cushioning for the brain

D. Structure And Function Of The Vertebrate Brain

1. The Vertebrate Brain Develops From Three Anterior Bulges of the Spinal Chord

a. The three anterior bulges are the forebrain, midbrain, hindbrain

b. The telencephalon and diencephalon develop in the forebrain, mesencephalon develops in the midbrain, metencephalon and myelencephalon develops in the hindbrain

2. The Brainstem Conducts Data and Controls Automatic activities Essential for Survival

a. The mesecephalon and part of the metencephalon and the myelencephalon combine to form the brainstem

b. The medulla oblongata controls breathing, heart rate, blood vessel activity, swallowing and digestion, pons also participate in a few of these activities

3. Cerebellum

a. The cerebellum develops frompart of the metencphalon and controls movement as well as balance

4. The Thalamus and Hypothalamus

a. Epithalamus includes a projection, the pineal gland and choroid plexus

b. The thalamus is an input center for sensory information going to the cerebrum, and the main output center for motor information leaving the cerebrum

c. The hypothalamus contains the body’s thermostat, regulates hunger, thirst and other survival mechanisms, and plays a role in sexual response and mating behaviors, the fight or flight response and pleasure

5. Cerebrum

a. The cerebrum is the most complex integrating center of the CNS, it develops from the telencephalon and is divides into two cerebral hemispheres

b. It has a covering of gray matter which is the cerebral cortex, and internal white matter

c. Within the white matter there is a cluster of nuclei called the basal nuclei, which are important centers for motor coordination, acting as switches for impulses from other motor systems

d. The cerebral cortex is the most complex part of the human brain its sophistication is based on its size and convulsions that give it a large surface area

e. The corpus callosum connects the two hemispheres together. The brain has four lobes each with different functions

1. 1. The Human Brain is a Major Research Frontier

a. The activity of the brain can be recorded in an electroencephalogram. In an EEG the less mental activity, the more synchronous the brain waves are

b. When an awake person is quiet and relaxed they create slow, synchronous alpha waves

c. When a person is awake during intense mental activity desynchronized beta waves occur

d. The REM sleep, when the eyes move actively across the visual field behind closed lids. This is when dreaming occurs

e. The brain’s hemispheres are specialized for different functions. The processes for speech, language, calculation, and the rapid serial processing of detailed information occur in the left hemisphere. The right hemisphere supports overall context, spatial perception, and creative abilities

f. Memory has two stages short and long term. There are skill and fact habits

g. Consciousness is subjective awareness or the ability to be aware of and make conscious judgments about the environment

Chapter 49

Sensory and Motor Mechanisms

A. Introductory to Sensory Reception

a. Information is transmitted through the nervous system in the form of nerve pulses or action potentials

b. What matters is what part of the brain the impulses go and not where they were triggered

c. A sensation is action potentials that reach the brain via sensory neurons

d. The brain interprets the sensation and gives us the perception of the stimuli, such as colors, smells, sounds, and tastes

2. Sensory Receptors Transduce Stimulus Energy and Transmit Signals to the Nervous System

a. Sensations and the perception they induce in the brain begin with the sensory reception which is the detection of the energy of a stimulus by sensory cells

b. Sensory receptors that are called exteroreceptors detect stimuli outside the body such as heat and light, introreceptors detect stimuli inside the body such as blood pressure and body position

c. Sensory transduction is the actual detection of a stimulus involving the conversion of stimulus energy into change in the membrane potential of a receptor cell

d. The initial response of the sensory receptor to a stimulus is a change in its membrane permeability, resulting in a graded change in membrane potential

e. Amplification is the strengthening of stimulus energy that is otherwise too weak to be carried into the nervous system

f. Once the energy in the stimulus has been transduced into a receptor potential, transmission or the conduction of impulses to the CNS

g. The processing of information or integration begins as soon as the information is received, the signals from the receptors are integrated through the summation of graded potentials

h. Sensory adaptation is a decrease in responsiveness during continued stimulation

3. Sensory Receptors are Categorized by the Type of Energy They Transduce

a. Based on the type of energy they transduce sensory receptors fall into five categories, mechanoreceptors, pain receptors, thermoreceptors, chemoreceptors and electromagnetic receptors

b. Mechanoreceptors are stimulated by physical deformation caused by such stimuli as pressure, touch, stretch ,motion, and sound, the hair cell is a common type of mechanoreceptor that detects motion

c. Pain receptors in humans are a class of naked dendrites in the epidermis of the skin called nociceptors, Pain is very important because it let the body know when to move away from danger

d. Thermoreceptors respond to either heat or cold, they help regulate body temperature by signaling the surface and the core

e. Chemoreceptors include general receptors that transmit information about total solute concentration and specific receptors that respond to individual molecules gustatory (taste) olfactory (smell)

f. Electromagnetic receptors detect various forms of electromagnetic energy such as visible light, electricity, and magnetism, Photoreceptors detect the radiation known as light

B. Photoreceptors

1. A Broad Array of Photoreceptors has Evolved Among Vertebrates

a. Most invertebrates have photoreceptors that range from a small cluster of cells to complex forming eyes

b. The eye cup of the planarian is possibly the simplest form, it can detect light intensity and direction but no actual image

c. Image forming eyes have two major types the compound eye and the single lens eye

d. Compound eyes are found in insects, crustaceans and some polychaete worms

e. A compound eye consists of several thousand light detectors called ommatidia

2. Vertebrates Have Single-Lens Eyes

a. The human eye is able to detect a variety of colors, form images of object from miles away, and respond to as little as a photon of light

b. Sclera is the tough white outer layer made up of connective tissue, at the front of the sclera where it becomes transparent is the location of the cornea

c. The anterior choroid forms the doughnut shaped iris which give the eye color, pupil is the hole in the center of the iris

d. The retina is the innermost layer of the eye and contains photoreceptor cells

e. The lens is suspended between two chambers in the eye which focus light on the retina

3. The Light Absorbing Pigment Rhodopsin Operates Via Signal Transduction

a. Transduction of the light signal occurs in specialized photoreceptors called rods and cones, which contain light absorbing retinal bonded to specific membrane proteins, collectively called opsins

b. Retinal is a light absorbing pigment and rhodopsin is a visual pigment

c. When rods and cones absorb light signal transduction pathways hyperpolarize their membrane and they release neurotransmitters

d. Photopsins are opsin associated with retinal to form visual pigments

4. The Retina Assists the Cerebral Cortex in Processing Visual Information

a. Chemical signals are transmitter from rods and cones to bipolar cells and then to ganglion cells whose axons in the optic nerve convey action potential to the brain

b. Other neurons in the retina integrate information before it is sent to the brain

c. Most axons of the optic nerves go to the lateral geniculate nuclei of the thalamus from which neurons lead to the primary visual cortex

C. Hearing And Equilibrium

1. The Mammalian Hearing Organ is Within the Inner Ear

a. The outer ear consist of external pinna and the auditory canal which collect sound waves and chanell them to the tympanic membrane or ear drum

b. The middle brain contain small bones that vibrate the malleus (hammer), the incus (anvil), and the stapes (stirrup)

c. The inner ear involved in hearing is the complex coiled organ known as the cochlea

d. Pressure waves vibrate the basilar membrane and the attached organ of corti which contains receptor hair cells

e. The ending of these hairs against the tectorial membrane depolarizes the hair cells triggering action potentials in the auditory nerve to the brain

2. The Inner Ear Also Contains the Organs for Equilibrium

a. Several organs in the inner ear of humans help detect balance and body position

b. The utricle, saccule and the three semicircular canals function in balance and equilibrium

c. The utricle opens into three semicircular canals that complete the apparatus for equilibrium

3. A Lateral Line System and Inner Ear Detect Pressure Waves in Most Fish

a. Like many vertebrate fish and other aquatic amphibians have inner ears located near the brain

b. The detection of water movements in fish an d aquatic amphibian is accomplished by a lateral line system of clustered hair cell receptors

4. Many Invertebrates Have Gravity Sensors and Are Sound Sensitive

a. Most invertebrates have sensory organs called statocysts that contain mechanoreceptors and function as their sense of equilibrium

b. Statoliths is a common type of statocysts that has a layer of hair cells

D. Chemoreception Taste and Smell

1. Perception of Taste and Smell are Usually Interrelated

a. Taste and smell depend on chemoreceptor that detect a specific chemical in the environment

b. The taste receptors on insects are located within sensory hairs called sensillae which are located on their feet and mouths

c. Humans as well as other mammals have their receptor cells for taste in organized taste buds on the tongue and mouth

d. Olfactory receptor cells line the upper part of the nasal cavity and send the olfactory bulb to the brain

E. Movement and Locomotion

1. Locomotion requires Energy to Overcome Friction and Gravity

a. Locomotion is the active travel from place to place

b. Animals can crawl, walk, run, or hop, flying has evolved in only a few animal groups of insects, birds, reptiles and a few mammals

c. Swimming makes gravity easier to overcome however fiction is a bigger problem in the water than in the air, aquatic animals have many different methods of moving through the water

d. On land gravity is the main obstacle and the leg muscles must support he body and overcome inertia at the same time, crawling takes a considerable amount of energy because of the friction

e. Gravity poses as an even greater problem for flying animals, wings have to overcome gravities downward pull

2. Skeletons Support and Protect the Animal Body and are Essential to Movement

a. A hydrostatic skeleton found in most cnidarians, flatworms, nematodes and annelids, consist of fluid under pressure in a closed body compartment

b. Hydrostatic skeletons support peristaltic locomotion produced by rhythmic waves of muscle contractions passing from head to tail of many worms

c. Exoskeletons, found in most mollusks and arthropods, are hard coverings deposited on the surface of an animal,

d. Endoskeleton is found in sponges, echinoderms and chordates and has hard supporting elements embedded within the body

e. Skeletal muscle is striated because the arrangement is a repeating pattern of light and dark bands, each repeating unit is sarcomere

f. Z lines are lined up in adjacent myofibrils and contribute to the striations

g. The I band is the area near the edge of the sarcomere where there are only thin elements, the A band is the broad region that corresponds to the length of the thick filaments

3. Interaction Between Myosin and Actin Underlie Muscle Contractions

a. When muscles contract the distance from one Z line to the next become shorten, The A bands do not change in length but the I band shortens as the H zone disappears this is called sliding-filament model

b. The energized myosin binds to a specific site on actin to form a cross bridge

c. Muscles store ATP for contractions but the energy needed for repetitive muscle contractions are stored in the phosphages, Creatine phosphate can supply the phosphate group with ADP to make ATP

4. Calcium Ion and Regulatory Proteins Control Muscle Contraction

a. Contraction begins when impulses from the motor neuron are transmitted to the muscle cell membrane through the release of acetylcholine at the neuromuscular junction

b. Action Potentials travel to the interior of the cell along the T tubules, which are plasma membranes, stimulating the release of calcium ions from the sarcoplasmic reticulum

c. The calcium ions bind to regulatory troponin-tropomyosin complex on the filaments exposing the myosin binding sites of the actin

5. Diverse Body Movements Require Variation in Muscle Activity

a. Whole muscle action can be controlled but at the cellular level its an all or none contraction

b. A single muscle action looks like a twitch, but as the muscles continue to move the twitches blur together this is called tetanus

c. A motor unit consist of a single motor neuron and all the muscle fibers it controls

d. Tension in the muscle can be progressively increased by activating more and more of the motor neurons controlling the muscle in a process called recruitment of motor neurons

Fast muscle fibers are rapid powerful contractions such as flight muscle in birds, slow muscle fibers can