11 - Animal Physiology

11.1 - Antibody Production / Immunity & Understandings

1. Every organism has unique molecules on the surface of its cells

2. Pathogens can be species-specific although others can cross species barriers

3. B lymphocytes are activated by T lymphocytes in mammals

4. Activated B cells multiply to form clones of plasma cells and memory cells

5. Plasma cells secrete antibodies

6. Antibodies aid the destruction of pathogens

7. White blood cells release histamine in response to allergens

8. Histamine causes allergic symptoms

9. Immunity depends on the persistance of memory cells

10. Vaccines contain antigens that trigger immunity but do not cause the disease

11. Fusion of a tumor cell with an antibody-producing cell creates a hybridoma cell

12. Monoclonal antibodies are produced by hybridoma cells

Physiology

studies the function of a living system, how organ systems, organs, cells and molecules carry out physical and biochemical functions, in this case immunity, movement, osmoregulation and reproduction.

Immunity

Immunity is the resistance to infections, based on whether the body can recognize whether certain cells and proteins are its own or foreign, if foreign material is found the body will defend itself and destroy it.

Pathogenesis

Pathogens are disease causing organisms such as bacteria, protists, fungi, parasites, viruses or prions. They contain antigens. Pathogenesis is the development of a disease. Diseases are conditions that disturb normal body function like homeostasis, and cause illnesses which worsen normal health.

Antigens

Antigens are the parts of the pathogen that are recognized as non-self and thus activate the immune system and cause an immune response. Antigens are found on the surface of pathogens, and typically are proteins, polysaccharides or both like glycoproteins,

How is immunity acquired?

Immunity is developed from infancy as the body is exposed to different pathogens that potentially cause disease, learns to recognize them, and distinguish between the ‘self’ and ‘non-self’. Cells are recognized due to proteins on plasma membranes.

Types of Immunity

Natural immunity results from being infected with a pathogen such as being immune to measles after being infected.

Artificial immunity comes from vaccines such as being immune to measles after vaccination.

Active immunity comes from your body producing its own antibodies such as the Rubella virus infection causes development of immunity.

Passive immunity comes from the antibodies received from another organism like your mom such as the antibodies received through placenta or colustrum.

How does cell recognition work and how are pathogens recognized?

White blood cells or leukocytes recognize and differentiate between the ‘self’ and the ‘nonself’ cells as all body cells contain the same set of plasma membrane proteins and cells with those specific proteins are recognized to be ‘self‘, whereas pathogens or transplanted organs have different membrane proteins and are recognized as ‘nonself’ cells or antigens.

In addition, MHC 1 Self-markers are found on all nucleated body cells and help identify cells as part of the organism or ‘self‘. Red blood cells are not nucleated and have no self-markers, but have basic antigenic markers.

What are the mechanisms of disease transmission?

Mnemonic: CAVE

Contamination - spreading pathogens via food

Airborne - spreading pathogens via sneezing or coughing

Vectors - intermediate organisms carry and spread pathogens without becoming symptomatic

Exchange - spreading pathogens via physical or bodily exchanges, like hugging or intercourse

Cell recognition in ABO and Rhesus blood types

Red blood cells or erythrocytes do not posses MHC 1 self-markers, but have basic antigenic markers or different plasma membrane proteins, A, B, both AB, and O meaning no surface glycoproteins. If the Rh protein is present then rhesus blood type is positive, Rh not present then negative.

A: cannot receive B or AB as B is foreign antigen.

B: cannot receive A or AB as A is foreign antigen.

AB: universal receiver as it possesses both antigens.

O: universal donor as no antibodies are present, but receives only O blood.

Leukocytes and Types

Leukocytes or white blood cells circulate in the bloodstream to defend the body against infection. Different types exist including lymphocytes and macrophages.

Macrophages or phagocytic leukocytes recognize antigens on pathogens, then engulf, partially digest pathogens, and present remaining antigens on its cell membranes for the Helper T cell to recognize.

Helper T lymphocytes play a role in adaptive immunity, recognize antigens presented by macrophages, switch the immune system from non-specific to antigen specific, and release cytokines to activate required B cells to make specific antibodies, as well as activate T Cytotoxic cells which can directly kill cells on antigens.

B lymphocytes or B cells divide and differentiate into plasma cells or memory cells, essentially antibodies.

Plasma cells produce specific antibodies that target specific antigens.

Memory cells remember specific antigens and circulate in the blood stream so if the pathogen reappears the immune system acts quickly.

Cytotoxic T-cells detect viral particles in the membrane of infected body cells and then destroy them, they can also identify some cancer cells.

Mammalian Immune Response Mechanism

Mammalian blood contains different types of B leukocytes, each type of B leukocytes or plasma cells can synthesize and secrete specific antibodies that bind to specific antigens. But, only 1% of all cells in the bloodstream are leukocytes which is not enough of each type of B cell for antibody secretion. Hence, for a specific antigen the cell communicates for the appropriate B-cell type cloning via mitosis.

1. Macrophages or large phagocytic cell leukocytes, first encounter antigens on pathogens, then engulf and partially digest pathogens via phagocytosis. This is non-specific.

2. The pathogen’s molecular remains or antigens are presented on the macrophage’s cell membrane, this is antigen presentation.

3. Helped T cell leukocytes in the blood recognize the antigen and activate.

4. Helper T cells switch the immune response from non-self to antigen-specific, then chemically communicate with and activate B-cells.

5. Activated B cells divide to form plasma cells which produce required antibodies and form memory cells.

6. The activated B cell undergoes mitotic cell division or cloning since daughter cells can produce the same antibody.

Incompatible blood transfusion

1. A+ donor gives blood to an B- recipient.

2. Recipient is receiving erythrocytes with two types of proteins that are incompatible with their genetic makeup.

3. The two donated proteins are recognized as antigens.

4. Antibodies are created and react against the non-self A and Rh antigens resulting in the cells to clump together or agglutination.

5. Agglutinated erythrocytes can clog and crack open the blood vessels.

6. Further causing erythrocyte destruction or hemolysis, releasing contents from its cytoplasm causing complications.

Antibodies

Antibodies are Y-shaped protein molecules made by differentiated B cells - plasma cells and respond to specific pathogen. At the ends of the ‘Y‘ fork there are two sequences of amino acids or binding sites that are unique to each antibody. The binding sites of each antibody are identical to each other and can bind to the same antigen.

Antibodies can bind to a pathogen and mark it for destruction, or use the two bind sites on two antigens clump them together for phagocytic cells to find and destroy, lastly can signal other cells and proteins to fight.

Antibody Production

1. Macrophages engulf antigens via endocytosis and attach them to membrane proteins called MHC proteins. The MHC protein with antigen is then moved to the plasma membrane by exocytosis and displayed on the surface of the macrophage.

2. Helper T cells have receptors that bind to antigens presented by the microphages. The macrophage binds to a Helper T cell hence changing the helper cell from inactive to active.

3. Inactive B cells have antibodies in their plasma membrane and if these antibodies match an antigen, the antigen binds to the antibody. And activate it helped her teeth sell with receptors from the same antigen can then bind to the B cell, T cell sends signal to B cell and activates it.

4. Activated B cells started divide via mitosis and produce plasma cells which have an extensive network of rough ER in order to synthesize large amounts of antibodies which are secreted by exocytosis, as well producing memory cells.

Monoclonal Antibodies and Uses

Monoclonal antibodies or mAbs, are identical artificial antibodies produced from a single B cell clone.

Therapeutic use: for the rabies virus we inject antibodies as emergency treatment, or to target cancer cells that one’s own immune cells don’t recognize as harmful.

Diagnostic use: pregnancy tests detect the presence of the hCG hormone which is produced during fetal development. Free mAbs specific to hCG are paired with a color changing enzyme, another set of mAbs specific to hCG are immobilized to the dye substrate, if hCG present it interacts and binds with both sets and changes color, third mAbs set binds unattached enzyme-linked antibodies as control.

Monoclonal Antibody Production

1. Animal is injected with antigen that produces required antibody, given some time animal undergoes primary immune response.

2. The differentiated B cells or plasma cells are extracted from the animal’s spleen.

3. Tumor cells capable of endless division are fused with the plasma cells producing hybridoma cells.

4. Hybridoma cells are capable of synthesizing large amounts of monoclonal antibodies which are then extracted and purified.

Antigen → Animal → Plasma Cells + Tumor Cells → Hybridoma cells = Monoclonal Antibodies

Vaccination

Vaccinations are composed of a pathogen’s chemical components minus disease-causing agents, and leukocytes activate the primary immune response mainly the formation of memory B cells resulting in immunity development. Vaccines don’t prevent infection but when exposed to pathogens, the secondary immune response is fast.

Pros: disease eradication, prevention of death, prevention of disabilities due to disease like rubella.

Cons: excessive vaccination reduces the ability of the immune system to respond to new disease, vaccination immunity as possibly not as effective as catching the disease naturally, possible that the vaccine against whooping cough causes brain damage and vaccine for MMR increases autism, people with weakened immune systems such as cancer patients or pregnant women can be harmed by cross infection from people vaccinated with a live virus.

Cross-species Diseases

Cross-species pathogenesis is rare as pathogens are usually species-specific, but some pathogens with the right conditions like “protein matching” can carry and cause disease cross species. Zoonotic diseases are transmitted from animal to humans, like rabies.

Allergens and Allergies

Allergens are non-pathogens that when encountered by certain B cells and cause an allergic response, like pollen. Initial exposure to a particular allergen causes B cells to different into plasma cells and produce a lot of IgE antibodies which bind to mast cells, a type of leukocytes,, priming them towards the allergen. During re-exposure the IgE antibodies bind to allergens triggering mast cells to release large amounts of histamine.

Histamine and Allergic Reactions

Histamine released from IgE-primed mast cells causes allergy symptoms, such as inflammation which improves leukocyte mobility to infected regions by triggering vasodilation and increasing capillary permeability. Vasodilation is the widening of blood vessels to improve blood circulation to specific regions, causing redness as blood moves closer to skin, along with heat transported in blood. Capillary permeability refers to leukocytes moving from the bloodstream into tissue, causing swelling as fluid leaks from blood, along with pain as nerves are compression. Severe allergic reaction is called anaphylaxis that could be fatal.

11.2 - Movement / Muscles & Understandings

1. Bones and exoskeletons provide anchorage for muscles and act as levers

2. Synovial joints allow certain movements but not others

3. Movement of the body requires muscles to work in antagonistic pairs

4. Skeletal muscle fibres are multinucleate and contain specialised endoplasmic reticulum

5. Muscle fibres contain many myofibrils

6. Each myofibril is made up of contractile sarcomeres

7. The contraction of the skeletal muscle is achieved by the sliding of actin and myosin filaments

8. ATP hydrolysis and cross bridge formation are necessary for the filaments to slide

9. Calcium ions and the proteins tropomyosin and troponin control muscle contractions

Levers

Levers consist of the bone and muscle to move weight. Bones functions as the lever arm for structure, joints function as fulcrum where the lever turns between two bones, muscles functions as a source of force to move the level

Skeletal Muscle

Function: Skeletal muscle is responsible for voluntary movement of bones.

Structure: It is attached to the skeleton and consists of multinucleated and heavily striated (long and thin) muscle fibers running in parallel tracts. Notice, there are slow and fast twitch muscle fibers.

Smooth Muscle

Function: Smooth muscle is responsible for involuntary constriction of internal organ linings, such as constriction of blood vessels or pupil dilation in the eyes.

Structure: Found in the lining of internal organs consisting of single-nucleated and spindle-shaped muscle fibers.

Cardiac Muscle

Function: Cardiac muscle is responsible for rhythmic heart contractions like the heart beat.

Structure: Found in the heart and consist of branched, single-nucleated, intercalated (positioned between two layers), and lightly striated fibers.

Slow Twitch Fibers

Function: Slow twitch fibers function for muscular endurance and contract slowly hence tire slowly, and use aerobic respiration for energy, prevalent in runners.

Structure: Large amount of mitochondria and blood vessels as slow twitch fibers rely on oxidative phosphorylation occurring in the mitochondria/ETC for ATP. Mostly red from abundant capillaries.

Fast Twitch Fibers

Function: Fast twitch fibers function for muscular strength and contract fast hence tire fast, and use anaerobic respiration, prevalent in strongmen.

Structure: Lesser mitochondria, blood vessels, and capillaries as fast twitch fibers do not rely on aerobic respiration, appear whiter.

Skeletal System

The skeletal system provides a rigid, structural framework to protect the organs. Levers or bones are connected to muscle by tendons for movement, ligaments connect two bones. Internal skeletons are endoskeleton, and external skeletons are exoskeleton consisting of many connected segments.

Synovial joints

Synovial joints surround and connect two bone surfaces to maintain structure and allow for different ranges of movement. From least mobile - planar joints like between foot bones, hinge joints like elbow, pivot joints like the neck vertebrae, ball and socket joints like the hip and femur.

Structure: joint capsules which seal the joint space and provide stability by restricting movement range. Cartilage which line bone surfaces for smooth movement, shock absorbance and load distribution. Synovial fluid which provides oxygen and nutrition to the cartilage and acts as lubricant to reduce friction

Elbow Joint

The elbow is a hinge joint located between the humerus, ulna and radius that is capable of angular movement in one direction, flexion and extension only, though small rotation can be possible but more will cause injury.

Bones: humerus connects to muscle, radius acts as forearm lever for biceps, ulna acts as forearm lever for triceps. Muscles: biceps bend the forearm as flexion, triceps straighten the forearm as extension.

Muscular System

The muscular system consists of skeletal muscles which connect to bones via tendons to provide force for movement. Muscles exist in antagonistic pairs one contracts and other relaxes for opposite movements, like flexion vs extension.

Antagonistic Pairs of Muscle Example

Insects like grasshoppers have specialized back legs for jumping. The jointed exoskeleton of the back leg is divided into the femur or upper leg, tibia or middle leg and tarsus or lower leg. Femur and tibia connected by flexor tibiae muscle and extensor tibiae muscle, antagonistic pair.

When flexor contracts the extensor relaxes, this pulls the tibia and femur together retracting the back legs to push off the ground. The extensor muscle contracts and flexor relaxes pushing tibia away from the femur.

Skeletal muscle and Muscle fiber structure

Skeletal muscles consist of tightly packaged muscular bundles or fascicles that are surrounded by connective tissue or perimysium. Bundles consist of many muscle fibers which form when singular muscle cells fuse. Muscle fibers contain tubular myofibrils along the fiber length. Myofibrils are divided into repeating sections called sarcomeres. Organization from smallest: Sarcomere, myofibril, muscle fiber, muscle bundle, muscle.

Muscle fibers form when individual muscle cells fuse hence multinucleated. They have abundant mitochondria for ATP hydrolysis and specialized ER, namely sarcoplasmic reticulum to store calcium ions. Tubular myofibrils consist of myofilaments, actin or thin filament and myosin or thick filament. Sarcolemma, the continuous membrane surrounding the muscle fiber contains infoldings called T tubules.

Muscle contraction

Contraction occurs when actin and myosin filaments slide over one another to shorten the muscle.

1. Initiated by the arrival of a action potential from a motor neuron that travels along the sarcolemma and move down into the t-tubules. Impulses spread along the sarcoplasmic reticulum releasing calcium ions.

2. In a relaxed state, troponin and tropomyosin cover myosin binding sites on actin filaments.

3. Calcium ions cause binding sites to become exposed and myosin heads bind to actin forming cross-bridged.

4. Myosin heads tilt, pulling actin and causes about a 10 millimeter contraction.

11.4 - Sexual Reproduction & Understandings

1. Spermatogenesis and oogenesis both involve mitosis, cell growth, two divisions of meiosis and differentiation

2. Processes in spermatogenesis and oogenesis result in different numbers of gametes with different amounts of cytoplasm

3. Fertilization in animals can be internal or external

4. Fertilization involves mechanisms that prevent polyspermy

5. Implantation of the blastocyst in the endometrium is essential for the continuation of pregnancy

6. hCG stimulates the ovary to secrete progesterone during early pregnancy

7. The placenta facilitates the exchange of materials between the mother and fetus

8. Estrogen and progesterone are secreted by the placenta once it has formed

9. Birth is mediated by positive feedback involving estrogen and oxytocin

Gametogenesis

Gametogenesis is the process of diploid precursor cells undergoing meiotic division to become haploid gametes or sex cells occurring in the gonads, glands producing reproductive hormones: ovaries and testes.

Gametogenesis involves mitosis, cell growth of precursor germ cells, meiosis I and II to form haploid cells, and differentiation of haploids. The female and male gametogenesis have several key differences:

In spermatogenesis cells divide equally during meiosis and produce four gametes, cells formed after differentiation are equal in size and cytoplasm, and gamete production is continuous after puberty till death.

Whereas in oogenesis cells don’t divide equally and produce one gamete along with 2 or 3 polar bodies, after differentiation one daughter cell being the ovum holds all the cytoplasm while other daughter cells form polar bodies which remain trapped within the follicle, and gamete production is not continuous beginning before birth, then according to menstruation and ends at menopause.

Spermatogenesis

Spermatogenesis is the production of male sex gametes or spermatozoa in the seminiferous tubules of the testes. Begins at puberty when germline epithelium of the seminiferous tubules divides by mitosis producing spermatogonia which after cell growth become spermatocytes, those undergo Mitosis I and II to form four haploid daughter cells, spermatids. Spermatids undergo differentiation and become functional sperm cells.

Spermatogonia 2n + mitosis + growth → spermatocyte-1 2n + meiosis I → 2 spermatocyte-2 + Meiosis II → 4 Spermatids + differentiation → 4 sperm

Oogenesis

Oogenesis is the production of female gametes or ova within the ovaries and oviduct.

1. Begins during fetal development when about 40.000 primordial cells form via mitosis.

2. The primordial cells after cell growth undergo mitosis to form primary oocytes.

3. Primary oocytes begin meiosis I, stopping at Prophase I when granulosa cells surround them to form follicles, and stay in Prophase I until puberty and beginning menstrual cycle.

4. Each months FSH hormones trigger continued division of some primary oocytes.

5. Primary oocytes undergo Meiosis I to form two unequal sized cells.

6. One cell takes the entire cytoplasm to form a secondary oocyte and other forms a polar body.

7. Polar body stays trapped within follicle until degeneration.

8. Secondary oocyte begins meiosis II, stopping at metaphase II.

9. Secondary oocyte is released from the ovary during ovulation and enters oviduct or fallopian tube.

10. Follicle cells surrounding the oocyte form corona radiata nourishing the secondary oocyte.

11. If a sperm fertilizes the oocyte, chemical changes trigger the completion of meiosis II and form another polar body.

12. Once meiosis II completes the mature eggs forms ovum, before fusing its nucleus with sperm nucleus to form zygote.

Seminiferous tubule and stages of spermatogenesis

Testes are composed of seminiferous tubules which produce sperm, each tubule surrounded by a basement membrane lined by germline epithelium that divides via mitosis to form spermatogonia which divides via meiosis into spermatids, they differentiate into functional spermatozoa which are released into the tubule lumen. The developing spermatozoa are nourished by Sertoli cells in the tubule lining. Outside the tubules are capillaries and interstitial cells producing testosterone.

Ovary and stages of oogenesis

The ovary contains follicles in various stages of development which develop over the menstrual cycle. Primordial follicles contain egg cells, primary oocytes locked in Prophase I. Some develop during menstruation into primary follicles and then into secondary follicles. Each cycle one follicles becomes a dominant Graafian follicle and ruptures releasing the secondary oocyte. The ruptured follicle develops into temporary corpus luteum secreting key ovarian hormones, before degenerating into corpus albicans.