CSIR NET Life Sciences System Physiology - Animal Syllabus

Name the phases of the cardiac cycle and their approximate durations at 75 bpm.

Atrial systole (~0.1 s), ventricular systole (~0.3 s), and joint diastole (~0.4 s); total cycle ~0.8 s.

Define stroke volume and cardiac output, and give the formula linking them.

Stroke volume = blood ejected per beat (~70 mL). Cardiac output = stroke volume x heart rate (~70 mL x 72 = ~5 L/min).

State the Frank-Starling law of the heart.

Within physiological limits, the force of ventricular contraction (stroke volume) increases with the end-diastolic volume (stretch of cardiac fibres) — the heart pumps the blood it receives.

What are normal systolic and diastolic blood pressure values, and how is pulse pressure calculated?

Normal ~120/80 mmHg (systolic/diastolic). Pulse pressure = systolic - diastolic = ~40 mmHg. Mean arterial pressure ≈ diastolic + 1/3 pulse pressure.

Where is the cardiovascular (vasomotor) centre, and name a key reflex regulating blood pressure.

In the medulla oblongata. The baroreceptor reflex: stretch receptors in the carotid sinus and aortic arch sense BP and adjust heart rate and vessel tone.

Compare the respiratory organs/mechanisms in fish, insects, amphibians, and mammals.

Fish: gills (countercurrent exchange); Insects: tracheal system delivering air directly to tissues; Amphibians: skin, buccal cavity, and lungs; Mammals: lungs with alveoli and diaphragm-driven ventilation.

What is countercurrent exchange in fish gills and why is it efficient?

Water flows over the gill lamellae opposite to blood flow, maintaining a diffusion gradient along the entire length so up to ~80-90% of dissolved O2 can be extracted.

In what forms is CO2 transported in the blood, and in what proportions?

As bicarbonate (HCO3-) ~70%, bound to haemoglobin as carbamino compounds ~20-23%, and dissolved in plasma ~7-10%.

What is the chloride shift (Hamburger phenomenon)?

In tissues, CO2 forms HCO3- in RBCs; as HCO3- diffuses out, Cl- moves into the RBC to maintain electrical neutrality. The reverse occurs in the lungs.

What is partial pressure, and how does it drive gas exchange at the alveoli?

Partial pressure is the pressure exerted by an individual gas in a mixture. O2 diffuses from high pO2 in alveoli (~100 mmHg) to low pO2 in capillary blood; CO2 diffuses the opposite way down its gradient.

Where is the respiratory rhythm centre located and what is the main chemical stimulus for increased breathing?

In the medulla oblongata (with the pons). The strongest stimulus is a rise in arterial CO2/H+ (decreased pH), detected by central and peripheral (carotid/aortic) chemoreceptors.

List the structural and functional regions of a typical neuron.

Dendrites (receive input), cell body/soma (integration, contains nucleus), axon (conducts impulse), axon terminals/synaptic knobs (release neurotransmitter); myelin sheath with nodes of Ranvier speeds conduction.

Describe the phases of an action potential.

Resting potential (~-70 mV); depolarization (Na+ influx to ~+30 mV); repolarization (K+ efflux); hyperpolarization (overshoot); then return to resting via Na+/K+ pump. It is all-or-none.

What is saltatory conduction?

In myelinated axons, the action potential 'jumps' from one node of Ranvier to the next, greatly increasing conduction velocity and energy efficiency.

Name the three major divisions of the vertebrate brain and a key structure in each.

Forebrain (cerebrum, thalamus, hypothalamus), Midbrain (optic lobes/corpora quadrigemina), Hindbrain (cerebellum, pons, medulla oblongata).

What are the functions of the cerebellum and medulla oblongata?

Cerebellum: coordination of movement, balance, posture and muscle tone. Medulla oblongata: control of vital involuntary functions — heart rate, breathing, blood pressure, reflexes like swallowing and vomiting.

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.

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.

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.

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.

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).

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).

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.

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.

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).

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).

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.

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.

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).

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.

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.

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.

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).

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.

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).

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.

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.

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.

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.

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.