Animal Physiology Flashcards
substances on cell surfaces and their uses
Every organism has unique molecules on the surface of their cells. Species have commonalities in that respect.
Viruses, which are not cells, also have unique mulches on their surface, usually a protein coat (capsid).
- viruses recognize and bind to their host
- living organisms recognize their own cells and cell types and identify foreign cells (antigens), triggering production of antibodies
Host specificity of pathogens
Some pathogens are species-specific (e.g. polio, measles and syphilis are human-specific)
Other pathogens are species-unspecific (e.g. tuberculosis, rabies; zoonosis is the ability of disease to pass from animals to humans)
Antigens on red blood cells
The ABO blood group system is based on the presence or absence of a group of glycoproteins in the membranes of red blood cells. Glycoproteins cause antibody production if antigens appear.
The O antigen is always present.
types of cells that secrete histamine, the function of it
and the connection to allergies
basophils, which are a type of white blood cell
mast cells, which are similar to basophils but are found in connective tissue
Histamine is secreted in response to local infections and causes the dilation of the small blood vessels in the infected area. As a result, the vessels become leaky, increasing the flow of fluid containing immune components to the infected area and allowing these components to leave the blood vessel, resulting in both specific and non-specific immune responses.
Allergies are reactions by the immune system to substances in the environment that are normally harmless, such as pollen, bee stings or specific foods (e.g. peanuts). Such substances cause over-activation of basophils and mast cells and therefore excessive secretion of histamine. This causes the symptoms associated with allergies: inflammation (swelling) of tissues, itching, mucus secretion, sneezing and also more dangerously, allergic rashes and extreme swelling known as anaphylaxis. Anti-histamine drugs exist.
Stages in antibody production
1. Activation of helper T-cells
One specific antigen can bind to their antibody-like receptor protein in their plasma membrane. The antigen is brought to the helper T-cell by a macrophage — a type of phagocytic white blood.
Binding = activation
2. Activation of B-cells
Inactive B-cells have antibodies in their plasma membrane. If these antibodies match an antigen, the antigen binds to the antibody. An activated helper T-cell with receptors for the same antigen can bind to the B-cell, and when it does, it sends a signal to the B-cell, activating it.
3. Production of plasma cells
Activated B-cells start to divide by mitosis to form clones, known as plasma cells. These plasma cells become active, with a much greater volume of cytoplasm and a very extensive network of rough endoplasmic reticulum, used for the synthesis of large amounts of antibodies, secreted by exocytosis.
4. Production of memory cells
Some cells persist to allow a rapid response if the disease is reencountered — giving long-term immunity.
roles of antibodies and the two regions of anitbodies with their function
The tips of the variable region are the antigen binding sites. The constant region aids the destruction of the pathogen. Different versions of the constant region have different ways to destroy:
- making a pathogen more recognizable to phagocytes to they are more readily engulfed (opsonization)
- preventing viruses from docking to host cells
- neutralizing toxins produced by pathogens
- binding to the surface of a pathogen cell and bursting it by causing the formation of pores
- sticking pathogens together (agglutination) so they cannot enter hosts cels and phagocytes can ingest them more easily
vaccination (+jenner and smallpox vaccination)
Vaccines contain antigens that trigger immunity to a disease without actually causing the disease in the person who is vaccinated. They contain weakened or killed forms of the pathogens or sometimes just contain the chemical that acts as the antigen. They stimulate the production of antibodies needed to control the disease, which sometimes requires multiple vaccinations.
The first vaccination causes a little antibody production and the production of some memory cells. The second vaccination, the booster shot, causes a response from he memory cells and therefore faster and greater production of antibodies.
Jenner and smallpox vaccination
Smallpox was the first infectious disease of humans to have been eradicated by vaccination, done by a worldwide vaccination program in the 1960s and 70s.
Edward Jenner had unethical experiments with children to test the first ever vaccine, using a less dangerous version of smallpox called cowpox.
analysis of epidemiological data
Epidemiology is the study of distribution, patterns and causes of disease in a population. Data can show where further vaccination is required to prevent further spread of the disease.
artificial production of large amounts of monoclonal antibodies and uses
Antigens that correspond to a desired antibody are injected into an animal. Plasma cells producing the desired antibody are extracted from the animal. Tumour cells that grow and divide endlessly are obtained from a culture. The plasma cells are fused with the tumour cells to produce hybridoma cells, which divide endlessly to produce a clone of one specific type of hybridoma cell. The antibodies that they produce are extracted and purified — these are monoclonal antibodies.
One of many uses of monoclonal antibodies lies in pregnancy test. The urine of pregnant women contains hCG, a protein secreted by the developing embryo and later by the placenta. Specific monoclonal antibodies bind to hCG, causing a colored band to appear, indicating pregnancy.
Structure of skeletal muscle
Skeletal muscle is attached to bone and causes movement and stability. It consists of large multinucleate cells called muscle fibers. Within each muscle fiber are cylindrical structures called myofibrils and around these is sarcoplasmic reticulum (special endoplasmic reticulum).
Myofibrils consist of repeating units called sarcomeres, which have light and dark bands. The light and dark bands extend across all the myofibrils in a muscle fiber. Each sarcomere is able to contract and exert force.
measuring sarcomere lengths with light microscopes
- Measure distance in mm from start of one dark band to start of a dark band ten bands away.
- Divide by ten = length of one sarcomere
- convert this length into micrometers by multiplying by a 1000
- Find actual length of a sarcomere by diving this length by the magnification of micrograph.
Alternatively, a slide of skeletal muscle and a microscope with an eyepiece scale can also measure sarcomeres, after calibration of units is done using a slider called stage micrometer.
structure of a sarcomere
- sarcomere = subunit of myofibril*
- Z line marks end of one sarcomere, to which thin actin filaments are attached
- the actin filaments stretch inwards towards the centre of the sarcomere
- between actin filaments are thicker myosin filaments, which have heads to form cross-bridges by binding to the actin
- myosin creates dark bands, parts of only filaments create light bands
Contraction: sliding filaments
During contraction the actin and myosin filaments slide over each other, pulling the ends of sarcomeres together, making the muscle shorter, which requires ATP.
The hydrolysis of one molecule of ATP provides enough energy for a myosin filament to slide the small distance along an actin filament. Repeated cycles of events result in sufficient contraction.
Control of muscle contraction
(+ what has been used to investigated contraction?)
A motor neuron stimulates a striated muscle fibre via calcium ions that are released from the sarcoplasmic reticulum inside the fibre. The calcium binds to troponin, a protein that is associated with the actin filaments in muscle. The calcium causes the shape of troponin to change and this causes the movement of tropomyosin, another protein associated with actin, exposing binding sites on acting. This allows myosin heads to form cross-bridges by binding to actin.
Radioactive calcium (45Ca) has been used to investigate the control of muscle contraction. Autoradiography showed that radioactive calcium is concentrated in the region of overlap between actin and myosin filaments in contracted muscle, but not in relaxed muscle.
mechanism of muscle contraction
The sliding of active filaments over myosin filaments towards the center of the sarcomere is achieved by a repeated cycle, in which cross-bridges are formed and broken and energy is released by hydrolysis of ATP.
how to muscles create movement
what types of muscles are invovled
As muscles can only exert force with contraction not when they relax and lengthen, a muscle can only cause movement in one direction. For opposite movements there has to be a pair of muscles that exert force in opposite directions — antagonistic muscle pairs (e.g. elbow: triceps and biceps).
tendon — tough band of connective tissue attaching muscle to bone
anchorage — a firm point of attachment, bones in humans, of one end of the muscle (insects use exoskeletons); it does not move during contraction
insertion — opposite to the anchorage of the muscle; bones or exoskeletons; move during contraction
levers (“Hebelarm”) — bones and exoskeletons, combined with muscles, act as levers during contraction
synovial joints
Some joints (_junctions between bone_s) are fixed, like joints between the plates of bone in the skull. Others allow movement (articulation), most of them being synovial joints, which have the following characteristics:
- cartilage covering the surface of bones to reduce friction where they could rub against each other
- synovial fluid between the cartilage-covered surfaces to lubricate joints and further reduce friction
- joint capsule that seals the joint and holds in the synovial fluid
- ligaments are tough cords of tissue connecting the bones on opposite sides of a joint (bone2bone). They restrict movement to prevent dislocation.
Antagonistic muscles in an insect leg
Insects commonly have joints that can either flex or extend. For example, legs of crickets have two large muscles inside the femur. The tendons at the distal sends of these muscles are attached to opposite sides of the exoskeleton of the tibia, so on elf them is a flexor of the joint between the femur and tibia and the other is an extensor.
Fluorescent calcium ions have been used to study the cyclic interactions in muscle contraction. For experiments, jelly fish produce a calcium-sensitive bioluminescent protein, aequorin (electromagnetic radiation). With this technique, researchers were able to demonstrate the ATP-dependence of myosin-actin interaction.
nitrogenous waste products
Two trends can be seen in this table:
1. The type of type of nitrogenous waste in animals correlates with habitat.
• Ammonia is toxic and has to be exerted as a very dilute solution, so a large volume of water is required. Hence only aquatic animals excrete ammonia.
• Urea is less toxic, so it can be more concentrated with less water. Conversion of ammonia to urea requires energy but it is worthwhile if an animal needs to conserve water.
• Uric acid is only very weakly toxic. Conversion of ammonia to uric acid requires much energy, but is worthwhile for animals that live in arid habitats with significant water conservation. It also benefits animals that fly, as concentrated paste of uric acid contains less water than dilute urine, reducing body mass during flight.
2. The type of nitrogenous waste in animals correlates with evolutionary history.
• For example, mammals excrete urea, even though some mammals such as beavers and otters live in aquatic habitats and do not need to conserve water but do so anyway, like terrestrial mammals.
why and how do some animals produce very concentrated urine
conserve water
A positive correlation between thickness of the medulla compared to the overall size of the kidney, and the need for water conservation. This is because a thicker medulla allows the loops of Henlé and collecting ducts to be longer, so more water can be reabsorbed and the urine can be made more concentrated.
structure and function of the kidney
Function: excretion and osmoregulation
Structure: the cortex and medulla contain many narrow tubes called nephrons. The renal pelvis consists of spongy tissue into which urine drains from collecting ducts.
structure and function of the nephron
A group of nephrons join up to form one collecting duct.
The human kidney contains about 1 million nephrons.
- The glomerulus and Bowman’s capsule produce a filtrate from the blood by ultrafiltration.
- The proximal convoluted tubule transfers useful substances from the filtrate back into the blood by selective reabsorption (active transport).
- The loop of Henlé establishes high solute concentrations in the medulla, so hypertonic urine can be produced.
- The distal convoluted tubule adjusts individual solute concentrations and the pH of the blood.
- The collecting dust carries out osmoregulation by varying the amount of water reabsorbed.
ultrafiltration
The glomerulus is a ball of blood capillaries, which leaks about 20% of its blood due to two reasons:
- very high blood pressure, because the vessel taking blood away from the glomerulus is narrower than the vessel bringing blood
- many large pores (fenestrations) in the capillary walls
These pores would allow any molecules through, but there are two filters that only allow small to medium sized particles to pass (68,000 molecular mass or less):
- basement membrane — a gel on the outside of the capillary with small gaps through a mesh of protein fibers
- filtration slits — narrow gaps between the foot process of podocyte cells where they wrap around the capillaries
The filtrate that enters the Bowman’s capsule contains all substances in blood plasma except plasma proteins.
selective reabsorption
Large volumes of glomerular filtrate are produced — about one liter every 10 minutes by two kidneys. The single-cell layered proximal convoluted tubule identifies useful substances from the waste and actively pumps them out (ATP and mitochondria). All glucose is reabsorbed and about 80% of mineral ions, including sodium.
Active transport of solutes makes the total solute concentration higher in the cells of the wall than in the filtrate in the tubule. Water therefore moves by osmosis from the filtrate to the cells and on into the adjacent blood.
role of the Loop of Henlé (part of a nephron)
Glomerular filtrate flows into the medulla in descending limbs and then back out to the context in ascending limbs.
contrasting permeability
• descending limbs are very permeable to water but are relatively impermeable to sodium ions; ascending limbs are the opposite.
Ascending limbs pump sodium ions from the filtrate into the medulla by active transport, creating a high solute concentration in the medulla. As the filtrate flows down the descending limb into this region of high solute concentration, some water is drawn out by osmosis. However, the filtrate that leaves the loop of Henlé is more dilute than the fluid entering it, showing that the overall effect of the loop is to increase the solute concentration of the medulla to hypertonic levels. Simply, the waste taken from the loop and collected in the medulla where the urine is taken to the bladder.
After the loop, the filtrate passes through the distal convoluted tubule, where ions can be exchanged between the filtrate and the blood (shown in yellow) to adjust blood levels. It then passes into the collecting duct.
Blood in the renal artery and vein
The composition of blood is altered as it flows through the kidney, so there are differences in the renal artery and vein.
two treatments of kidney failure (+description of the condition)
When the kidney fails, toxins build up and solute concentrations are not maintained at normal level. Untreated, it makes the patient increasingly ill and is eventually fatal. There are two treatments:
1. Hemodialysis
Blood is drawn out of a vein in the arm and passed through a kidney machine for 3 to 4 hours, 3 times per week. The blood flows next to a semi-permeable dialysis membrane with dialysate (a fluid) on the other side. Pores through the membrane allow small particles to diffuse in either direction, but plasma proteins and cells are retained in the blood. Dialysate has these features:
- no urea or other waste products, so they diffuse from the blood to the fluid
- ideal concentrations of glucose and other metabolites, so ideal concentrations are achieved in the blood by diffusion to or from the fluid
- high calcium and low potassium concentrations to extract potassium and add calcium to the blood
- hydrogen-carbonate ions (HCO3-) to reduce the acidity of blood
- a total solute concentration that will cause excess water to be removed from the blood by osmosis across the dialysis membrane
2. Kidney transplants
- Dialysis can keep patients alive for years, but a better long-term treatment is a kidney transplant.
- Living people can donate one kidney as humans only need one to survive (or recently dead).
- Donor and recipient should have the same blood group to minimize possible rejection by the immune system.
Exertion and water conservation
Some animals have relatively long loops of Henlé found in the medulla, because the length of the loop is positively correlated with the need for water conservation.
To conserve water, very concentrated urine is produced. The general trend in mammals:
A positive correlation between thickness of the medulla compared to the overall size of the kidney, and the need for water conservation. This is because a thicker medulla allows the loops of Henlé and collecting ducts to be longer, so more water can be reabsorbed and the urine can be made more concentrated.
insects: Malpighian tubule system
The circulatory system of insects uses hemolymph rather than blood. Hemolymph is pumped by a vessel that runs from the abdomen forwards through the thorax to the head. Branches of this vessel carry the hemolymph to different parts of the body and it is then released and is free to flow gradually through tissues until being drawn back into the vessel for re-pumping. Body cells are bathed in hemolymph and release waste products into it.
Between the midget and hindgut of insects there is a ringe of narrow blind-ended ducts, called Malpighian tubules, which end tend through the body cavity of the insects. Cells in the tubule walls extract waste products from the hemolymph and pass them into the lumen of the tubule. Ammonia is extracted and converted by Malpighian tubule cells into uric acid.
To create a flow of fluid that will carry uric acid and other waste along the Malpighian tubules to the hindgut, cells in the tubule wall transfer mineral ions by active transport from the hemolymph to the lumen of the tubule and water follows passively by osmosis. The solution that is produced in this way drains into the lumen of the hindgut where it mixes with the semi-digested food. The mixture is carried on to the last section of the gut — the rectum. Mineral ions are pumped by cells in the wall of the rectum from the feces in the rectum to the hemolymph and again water follows passively by osmosis. By moving solutes and water into and out of the hemolymph, the Malpighian tubules and rectum together prevent dehydration and achieve osmoregulation.
structure and functions of a mature human sperm
outline of spermatogenesis
Cells in the wall of the seminiferous tubule (testes tissue):
annotate
structure and functions of a mature human egg
outline of oogenesis
stages in fertilisation
Early embryo development and implantation
After sexual intercourse, semen is ejaculated into the vagina and sperm swims through the cervix, up the uterus and into the oviducts. If there is an eg in the oviducts, a sperm can fuse with it to produce a zygote.
It starts to divide by mitosis to form a two-cell embryo, then a four-cell embryo and so on until a hollow ball of cells called a blastocyst is formed. While these early stages of embryonic development happen, the embryo is transported down the oviduct to the uterus. When it is about 7 days old, the embryo impacts itself into the endometrium, where it continues to grow and develop. If implantation does not occur then the embryo is not supplied with enough food and the pregnancy stops.
Animal size and duration of gestation (pregnancy)
Although there is an overall positive correlation between body mass and length of gestation, there are exceptions. In animals with relatively long gestation, the offspring are more advanced in their development when they are born than animals with a short gestation time.
hornomal control of childbirth
- Through the 9 months of pregnancy, rising levels of the hormone progesterone ensures uterus development, sustaining the fetus, preventing uterine contractions and therefore spontaneous abortions.
- Progesterone concentrations decreases towards the end to allow the secretion of the hormone oxytocin.
- There is also a rise in estrogen, which causes an increase in the number of oxytocin receptors on the muscle in the uterus wall. When oxytocin binds to these receptors it causes the muscle to contract. Uterine contractions stimulate the secretion of more oxytocin. The uterine contractions therefore become progressively stronger — positive feedback.
- At immediate childbirth, the muscle in the wall of there uterus is contracting, the cervix relaxes and becomes wider. The amniotic sac bursts and the amniotic fluid is released. Often after many hours of contraction, the baby is pushed out through the cervix and the vagina. The umbilical cord is cut and the baby begins its independent life. Contractions continue for a time until the placenta is expelled as the afterbirth.
function of the placenta
By the time the embryo is about 8 weeks old, it starts to develop bone tissue and is known from then onwards as a fetus. The fetus develops a placenta and an umbilical cord. The placenta is a disc-shaped structure, with many projections called placental villi embedded in the uterus wall. In the placenta, the blood of the fetus flows close to the blood of the mother in the uterus wall. This facilitates the exchange of materials between maternal and fetal blood.
structure and function of the placenta
annotation of placenta
exchange of materials across the placenta
[other visualtion below]
