11. ANIMAL PHYSIOLOGY Flashcards
Describe the different cell types in the seminiferous tubules that are involved in the process of spermatogenesis.
[4]
- spermatogonia «2n» are undifferentiated germ cells
- spermatogonia mature and divide «by mitosis» into primary spermatocytes «2n»
- primary spermatocytes divide by meiosis I into secondary spermatocytes «1n»
- secondary spermatocytes divide by meiosis II into spermatids «1n»
- spermatids differentiate/mature into spermatozoa
f. Sertoli/nurse cells provide nourishment for the developing cells
Compare and contrast the processes of spermatogenesis and oogenesis. [8]
similarities:
- both involve mitosis at the start/in the «germinal» epithelium
- involve meiotic division producing
- preceded by growth
- produce haploid cells
- both involve differentiation to produce a gamete
Differences: spermatogenesis/ oogenesis
- stimulated by testosterone / stimulated by FSH
- testes/ovaries
- starts at puberty/starts at embryo development
- no pauses/ pauses at Prophase I and Prophase II
- 4 sperm cells per meiosis/ 1 egg cell per meiosis
- milions daily/ 1 per month
- released continuously/ only on about the 14th day of the cycle
- until death/ stops at menopause
Explain how insects excrete nitrogenous waste. [8]
- as uric acid (non-toxic)
- excreted by Malpighian tubules
- nitrogenous waste accumulates in insects’ hemoplymph
- is aborbed by Malphigian tubule
- ammonia is converted into uric acid with the use of ATP
- active transport of ions into Malphigian tubule
- water absorbed by osmosis flushes uric acid into the hindgut
- uric acid forms a paste so not a lot of water required
- it is excreted with feces
What does the blastcyst secrete?
HCG - it stimulates corpus lutheum (in the ovary) to continue to secrete progesterone
What mechanisms prevent polyspermy?
- Acrosome reaction - acrosome has enzymes that digest zona pellucida
- Penetration of egg cell membrane - sperm membrane has proteins on its tip that bind to egg cell mambrane, membranes fuse
- Cortical reaction - cortical granules secrete enzymes by exocytosis which digest receptor proteins and harden zona pellucida
Which hormone stimulates contraction of the myometrium?
Towards the end of pregnancy, placenta stops secreting estrogen and progesterone (which inhibited oxytocin secretion). Oxytocin ( released by the pituitary gland) stimulates the contraction of myometrium allowing the baby to be born.
Explain primary immune response mechanism
- macrophages engulf pathogens and display antigens on its surface
- specific helper-T cells recognize specific antigens and become activated
- they activate B cells that replicate
- some become memory cells and some become plasma cells and produce antibodies
- antibodies clump together pathogens
- mark pathogens which makes them easier to recognize by phagocytes
Explain the action of filaments.
- ATP binds to myosin head breaking the cross bridge between actin and myosin
- hydrolysis of ATP causes the myosin head to swivel and attach to a new actin binding site
- myosin head returns to the original configuration dragging actin along
- sarcomere shortens
- consequently resulting in muscle contraction
Distinguish between the composition of the blood of the renal artery and the blood of the renal vein.
renal artery - more glucose, more oxygen, more urea, salts and water in variable concentrations
renal vein- more CO2, salts in constant concentration, water balance at normal balance
Explain the role of kidneys in osmoregulation.
- osmoregulation is regulation of water and solute/salt balance/solute concentrations;
- kidneys remove waste products of metabolism
- functional unit of the kidney is a nephron
- ultrafiltration in the glomerulus filtrate collected by the Bowman’s capsule
- selective reabsorption in proximal convoluted tubule
- loop of Henle establishes hypertonic conditions in the medulla
- descending limb permeable to water/ ascending limb permeable to salts
- countercurrent blood flow
- water reabsorbed in the collecting duct whose aquaporines concentration is regulated by ADH
f. brain/hypothalamus monitors blood solute concentration / pituitary secretes ADH;
g. ADH secreted when solute concentration of blood is too high/hypertonic/when dehydrated;
h. ADH increases permeability of collecting duct to water;
i. ADH causes more aquaporins (in membranes of collecting duct wall cells);
j. more water reabsorbed resulting in more concentrated/hypertonic urine/less volume of urine;
k. less/no ADH secreted when solute concentration (of blood) is too low/hypotonic;
l. less water reabsorbed resulting in dilute/hypotonic urine/large volume of urine;
