Zoology: Homeostasis and Human Physiology
Zoology in NEET UG focuses on animal diversity, structural organisation, human physiology, reproduction, genetics and evolution, and human health. Human physiology carries the most numerical and conceptual weight: transport, respiration, excretion, neural control and endocrine regulation.
Core rules
- Homeostasis maintains internal stability through negative feedback; the nephron uses glomerular filtration, tubular reabsorption and secretion, with most reabsorption in the proximal convoluted tubule.
- Cardiac output = heart rate × stroke volume. The SA node is the normal pacemaker; the pulmonary artery carries deoxygenated blood to the lungs.
- Resting membrane potential is about -70 mV, maintained largely by K+ permeability and the Na+/K+ ATPase; depolarisation involves Na+ influx.
- Insulin lowers blood glucose; glucagon raises it; ADH increases water reabsorption in the collecting duct.
- Spermatogenesis produces four haploid sperm from one primary spermatocyte; oogenesis produces one ovum and polar bodies.
Worked example
A person has a heart rate of 70 beats/min and a stroke volume of 70 mL/beat. Cardiac output = 70 × 70 = 4900 mL/min = 4.9 L/min. If stroke volume rises to 80 mL/beat at the same heart rate, output becomes 5600 mL/min, or 5.6 L/min.
Traps
Calling the pulmonary artery oxygenated; naming the AV node as the pacemaker; placing most reabsorption in the loop of Henle rather than the PCT; saying insulin raises blood glucose; confusing ADH with aldosterone; forgetting that one primary spermatocyte yields four sperm.