Unit 11 - Animal Physiology Flashcards
(19 cards)
Outline the function of Sertoli cell. [1]
Nourishes the maturing sperm.
Explain the processes occurring in the kidney that contribute to osmoregulation. [8]
Osmoregulation is the control of the water balance of the blood, tissues, or cytoplasm of a living organism.
The descending limb of loop of Henle is only permeable to H2O, as the H2O is released, which makes the fluid more salty and hypertonic.
The ascending limb of loop of Henle is only permeable to salts, which releases the salts into the medulla, further establishing a salt gradient.
As the collecting duct passes through the medulla, the hypertonic conditions of the medulla will draw water out by osmosis.
The amount of H2O released from the collecting duct is to be retained by the body is controlled by ADH. ADH is released from posterior pituitary in response to dehydration.
ADH increases the permeability of H2O in collecting duct, by upregulating production of aquaporins. This means less H2O remains in the filtrate, as the urine becomes more concentrated and the individual urinates less. When an individual is hydrated, the ADH levels decrease and less H2O is reabsorbed.
Outline the functions of biceps and triceps. [2]
Biceps - Helps to bend arm at elbow (elbow flexion).
Triceps - Responsible for straightening arm at elbow (elbow extension).
Outline the function of cartilage. [1]
Allows smooth movement and adsorbs shock.
Outline the function of proximal and distal convoluted tubules.
Selectively reabsorbs useful substances from the filtrate by active transport, into the blood.
Describe the process of fertilization in humans. [6]
The sperm breaks through the breaks through the follicular cells of corona radiata and binds to the zona pellucida (jelly coat).
The acrosome vesicle fuses with the jelly coat and releases digestive enzymes which soften the zona pellucida. The sperm then pushes its way through the zona pellucida and binds to docking proteins on the egg membrane.
The membrane of the egg and sperm fuse with and then the sperm nucleus enters the egg.
Cortical granules within the egg’s cytoplasm release enzymes into the zona pellucida which destroy sperm binding sites, and also thicken and harden the zona pellucida, in order to prevent polyspermy.
Explain the principles of vaccination. [8]
A vaccine is a weakened form of the pathogen that contains antigens.
When the vaccine is introduced to the body by injection. Antigens in the vaccination causes antibody production. Antigens are engulfed by macrophage. A proportion of macrophages will present the antigenic fragments of the pathogen to specific helper T lymphocytes, when activated, it releases cytokines.
The cytokines stimulate a specific B cell that produces antibodies to the antigen to divide and form clones. Most of the clones will develop into short-lived plasma cells that produce large quantities of specific antibody.
A small proportion of clones will differentiate into long-lived memory cells that function to provide long-term immunity.
Outline the hormonal control of the process of birth. [4]
When the baby is fully grown and stretches the walls of the uterus, this stress induces the release of chemicals which trigger a rise in the level of estrogen.
Estrogen inhibits progesterone, which was preventing uterine contractions. The brain triggers the release of oxytocin from the posterior pituitary gland, which stimulates the uterine muscle to contract (initiating birth process).
The fetus responds to this contraction, and releases prostaglandins which trigger further contractions (positive feedback).
Contractions will stop after birth.
Outline the principles that form the basis of immunity. [6]
Skin and mucous membranes form barriers to pathogens a first line of defence.
Antigens are engulfed by macrophage. A proportion of macrophages will present the antigenic fragments of the pathogen to specific helper T lymphocytes, when activated, it releases cytokines.
The cytokines stimulate a specific B cell that produces antibodies to the antigen to divide and form clones. Most of the clones will develop into short-lived plasma cells that produce large quantities of specific antibody.
A small proportion of clones will differentiate into long-lived memory cells that function to provide long-term immunity.
Explain the structure and role of the placenta. [8]
The placenta is a disc-shaped structure which is embedded in uterus wall, that nourishes the developing fetus. Chorionic villi extend into the intervillous space mediate the exchange of materials between fetus and mother.
Exchanged materials are transported from the villi to the fetus, through the umbilical cord.
Chorionic villi are lined by microvilli to increase the surface for material exchange such as O2, vitamins, nutrients, antibodies and H2O will diffuse from the intervillous space into fetal capillaries.
Fetal capillaries within the chorionic villi, lies close to the surface of villi to minimise diffusion distance.
Fetal wastes such as CO2, urea and hormones will diffuse from the space into the maternal blood vessels.
State a function of interstitial cell. [1]
Produce testosterone
State a function of germinal epithelium cell. [1]
Will divide by mitosis to make spermatogonia
Explain how the structure and functions of the placenta maintain pregnancy. [8]
In placenta, the transport is facilitated by the mother and the embryo blood vessels. Chorionic villi extend into the intervillous space mediate the exchange of materials between fetus and mother.
Exchanged materials are transported from the villi to the fetus, through the umbilical cord. Chorionic villi are lined by microvilli to increase the surface for material exchange.
Immune system of mother protects the fetus from harmful substances. Placenta also acts as an endocrine organ, producing key hormones such as progesterone prevents uterine contractions, estrogen increases mammary gland growth, and both hormones maintain the endometrium.
HCG hormone signals pregnancy and supports progesterone production by preventing degeneration of corpus luteum. Progesterone also prevent uterine contractions.
Describe how spermatogenesis occurs in humans. [6]
Spermatogenesis is the production of sperm in the seminiferous tubules of the testes. The process begins at puberty when germinal epithelium of the seminiferous tubules divide my mitosis.
The germinal cells undergo mitotic divisions and cell growth, becoming spermatocytes.
Primary spermatocytes undergo meiosis I to form secondary spermatocytes.
These secondary spermatocytes undergo meiosis II to produce spermatids.
Spermatids differentiate in order to become functional sperm cells.
Explain how the nephron changes the composition of blood. [7]
- As the blood moves into the kidney via afferent arterioles, it enters glomerulus. Glomerular blood vessels have pores which can freely exit the blood from glomerulus.
- Between the glomerulus and the Bowman’s capsule there is a glycoprotein matrix called the basement membrane, is size-selective and restricts the passage of blood cells and large proteins. Most small soluble molecules such as H2O, glucose, salt, amino acids, and urea pass freely into the Bowman’s capsule.
Hence when the blood is filtered throughout, the filtrate doesn’t contain any blood cells, platelets or plasma proteins. This process is known as ultrafiltration.
- Selective reabsorption is a process which involves the reuptake of useful substances in the convoluted tubules. Mineral ions and vitamins are actively transported by protein pumps and carrier proteins. Glucose and amino acids are co-transported with sodium. Water follows the movement of mineral ions passively via osmosis. The urea still remains in the filtrate.
- Osmoregulation is the control of the water balance of the blood, tissues, or cytoplasm of a living organism. The descending limb of loop of Henle is only permeable to H2O, as the H2O is released, which makes the fluid more salty and hypertonic. The ascending limb of loop of Henle is only permeable to salts, which releases the salts into the medulla, further establishing a salt gradient.
As the collecting duct passes through the medulla, the hypertonic conditions of the medulla will draw water out by osmosis. ADH increases the permeability of H2O in collecting duct, by upregulating production of aquaporins.
State the role of tendons. [1]
Attach muscles to bones.
Distinguish between the composition of the blood of the renal artery and the blood of the renal vein. [3]
In renal vein:
- Less urea
- Less O2
- More CO2
- Less glucose
Explain muscle contraction. [8]
The part of a myofibril between one z-line and the next is called a sacromere. The overlapping thick-myosin filaments pull the thin-actin filaments inwards towards the centre of the sacromere, which shortens the sacromere and narrows the light bands.
In a relaxed muscle, tropomyosin blocks the binding sites on actin. Nerve impulses cause depolarisation of sarcoplasmic reticulum, and releases the calcium ions, to bind to troponin which causes tropomyosin to move, exposing actin’s binding sites. Heads of myosin filaments and binding sites of actin filaments form cross-bridges. The ATP binds to the myosin heads and breaks the cross-bridges.
Hydrolysis of ATP causes the myosin head to be cocked, as they store energy also. New cross-bridges are formed, binding of myosin heads to actin binding sites, which are further from the centre of sacromere.
Energy stored in the myosin head, causes it to swivel inwards towards the centre of sacromere (shortens sacromere).
