CSIR NET Life Sciences System Physiology - Animal Flashcards

24 sample cards from the System Physiology - Animal deck

Sampled from the end of the deck, so these are different cards from the ones shown on the syllabus page.

1. How is the peripheral nervous system subdivided?

   PNS = somatic nervous system (voluntary, skeletal muscle) + autonomic nervous system, which is further split into sympathetic ('fight or flight') and parasympathetic ('rest and digest') divisions.

2. What is a stretch (myotatic) reflex and its role in muscle tone/posture?

   A monosynaptic reflex (e.g., knee-jerk) in which muscle spindle stretch triggers reflex contraction of the same muscle, maintaining muscle tone and postural stability.

3. Trace the path of light and the photoreceptors in the human eye.

   Light passes cornea → aqueous humour → pupil → lens → vitreous humour → retina. Rods (dim light, monochrome) and cones (bright light, colour) are the photoreceptors; the photopigment in rods is rhodopsin.

4. How does the ear transduce sound, and which structure contains the auditory receptors?

   Sound vibrates the tympanum → ossicles (malleus, incus, stapes) → oval window → cochlear fluid. The organ of Corti on the basilar membrane (in the cochlea) holds hair cells that convert vibration to nerve impulses.

5. What are the main cutaneous (tactile) receptors and their stimuli?

   Meissner's corpuscles (light touch), Pacinian corpuscles (deep pressure/vibration), Merkel discs (sustained touch/texture), Ruffini endings (stretch), free nerve endings (pain, temperature).

6. Compare ammonotelic, ureotelic, and uricotelic excretion with examples.

   Ammonotelic: excrete ammonia, needs much water (bony fish, aquatic invertebrates). Ureotelic: excrete urea (mammals, amphibians). Uricotelic: excrete uric acid, water-conserving (birds, reptiles, insects).

7. Name the parts of a nephron in order of filtrate flow.

   Bowman's capsule (glomerulus) → proximal convoluted tubule → loop of Henle (descending + ascending limbs) → distal convoluted tubule → collecting duct.

8. List the three basic processes of urine formation.

   Glomerular filtration (in Bowman's capsule), tubular reabsorption (mostly PCT), and tubular secretion; the modified filtrate becomes urine.

9. How does the loop of Henle help concentrate urine?

   It establishes a countercurrent multiplier: the ascending limb pumps out NaCl (impermeable to water) and the descending limb loses water, creating a hyperosmotic medullary gradient that draws water from the collecting duct (under ADH).

10. What is micturition and how is it controlled?

    Micturition is the expulsion of urine from the bladder. Stretch receptors trigger a spinal reflex relaxing the internal sphincter; voluntary control of the external (skeletal) sphincter is via the brain (pons micturition centre).

11. Which two hormones regulate water and Na+ balance via the kidney, and how?

    ADH (vasopressin) increases water reabsorption in the collecting duct (concentrates urine). Aldosterone (from the adrenal cortex, via renin-angiotensin) increases Na+ reabsorption and K+ secretion in the DCT, raising blood volume/pressure.

12. What is the comfort (thermoneutral) zone?

    The range of ambient temperature in which a homeotherm maintains body temperature with minimal metabolic effort (no shivering or sweating); for humans roughly 25-30°C.

13. Distinguish endotherms (homeotherms) from ectotherms (poikilotherms).

    Endotherms/homeotherms generate heat metabolically and keep a constant body temperature (birds, mammals). Ectotherms/poikilotherms depend on environmental heat and have variable body temperature (fish, amphibians, reptiles).

14. Which brain centre regulates body temperature and name one heat-loss and one heat-gain response.

    The hypothalamus. Heat loss: vasodilation and sweating. Heat gain/conservation: shivering, vasoconstriction, and increased metabolic (thyroxine-driven) heat production.

15. What is acclimatization?

    Reversible physiological adjustment of an organism to a changed natural environment (e.g., increased RBC count and breathing rate at high altitude), occurring over days to weeks within the individual's lifetime.

16. Where are the major digestive enzymes secreted and what do they act on?

    Salivary amylase (mouth, starch); pepsin (stomach, proteins); pancreatic amylase, trypsin/chymotrypsin (proteins), lipase (fats) in the duodenum; intestinal disaccharidases and peptidases complete digestion.

17. Where and how are the products of digestion absorbed?

    Mainly in the small intestine across villi/microvilli: glucose and amino acids by active transport into blood capillaries; fatty acids and glycerol re-form into chylomicrons entering lacteals (lymph).

18. Define BMR and name a major factor that affects it.

    Basal Metabolic Rate is the minimum energy expended at complete rest, fasting, in a thermoneutral environment. It is raised by thyroid hormone (thyroxine); it also varies with body surface area, age, sex and muscle mass.

19. Name the major endocrine glands and one principal hormone of each.

    Pituitary (GH/ACTH), Thyroid (thyroxine), Parathyroid (PTH), Adrenal (cortisol/adrenaline), Pancreas (insulin/glucagon), Gonads (testosterone/estrogen), Pineal (melatonin).

20. Contrast the mechanism of action of peptide vs steroid hormones.

    Peptide/amine hormones bind cell-surface receptors and act via second messengers (e.g., cAMP) — fast, no new gene expression. Steroid (and thyroid) hormones are lipid-soluble, enter the cell, bind intracellular receptors and regulate gene transcription — slower, longer-lasting.

21. Match these endocrine disorders to their hormone defect: diabetes mellitus, goitre, acromegaly, Addison's disease.

    Diabetes mellitus — insulin deficiency/resistance; goitre — iodine/thyroid hormone deficiency (thyroid enlargement); acromegaly — excess growth hormone in adults; Addison's disease — adrenocortical (cortisol/aldosterone) insufficiency.

22. Define spermatogenesis and oogenesis and state how many functional gametes each yields per primary cell.

    Spermatogenesis: one primary spermatocyte → 4 functional sperm (via meiosis). Oogenesis: one primary oocyte → 1 functional ovum + 2-3 polar bodies.

23. Describe the hormonal control of ovulation in the menstrual cycle.

    Hypothalamic GnRH stimulates pituitary FSH (follicle growth) and LH; rising estrogen triggers an LH surge that causes ovulation (~day 14); the ruptured follicle becomes the corpus luteum secreting progesterone.

24. What is the hypothalamo-hypophyseal axis (neuroendocrine regulation)?

    The hypothalamus links the nervous and endocrine systems: it secretes releasing/inhibiting hormones to the anterior pituitary via a portal system, and produces ADH and oxytocin stored/released by the posterior pituitary — integrating neural signals into endocrine output.

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