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.