Physiology — 30-Min Notes

1. Cardiovascular Physiology

• Heart rate: normal 60–100 bpm; regulated by SA node and autonomic input.

• Cardiac output = HR × Stroke volume; average ~5 L/min at rest.

• Blood pressure regulation: short-term → baroreceptors; long-term → RAAS system.

• High-yield: Starling’s law → stroke volume ↑ with increased preload

• Tip: Ejection fraction = SV / EDV × 100%; normal ~55–70%

2. Respiratory Physiology

• Tidal volume ~500 mL, RV ~1200 mL, VC ~4500 mL, total lung capacity ~5700 mL.

• Alveolar gas exchange depends on partial pressures; O2 → 100 mmHg, CO2 → 40 mmHg in alveoli.

• High-yield: O2 dissociation curve → shifts right (↑CO2, ↑H+, ↑Temp) facilitate O2 release

• Tip: Pulmonary function tests differentiate obstructive (FEV1↓) vs restrictive (TLC↓) lung disease

• Respiratory centers: medullary (dorsal & ventral) and pontine centers regulate rhythm

3. Renal Physiology

• Glomerular filtration rate (GFR) ~120 mL/min; regulated by afferent/efferent arterioles and RAAS.

• Renal handling: filtration → reabsorption → secretion; key for electrolyte and acid-base balance.

• High-yield: ADH → inserts aquaporins in collecting ducts → water reabsorption

• Tip: Aldosterone → Na+ retention, K+ excretion; important in hypertension

• Countercurrent mechanism maintains medullary gradient → concentrated urine

4. Gastrointestinal Physiology

• Saliva → amylase for starch digestion; gastric secretion → HCl and pepsin.

• Small intestine: absorption of nutrients (duodenum → Fe, jejunum → carbs/proteins, ileum → B12, bile salts).

• High-yield: Intrinsic factor essential for B12 absorption → pernicious anemia if deficient

• Motility: peristalsis moves food; segmentation mixes chyme.

• Tip: Liver → bile secretion, detoxification; Pancreas → endocrine (insulin, glucagon) and exocrine (enzymes)

5. Endocrine Physiology

• Hypothalamus → pituitary axis regulates growth, thyroid, adrenal, gonads.

• Thyroid hormones ↑ basal metabolic rate; calcitonin ↓ blood calcium.

• High-yield: Parathyroid hormone ↑ Ca2+, ↓ phosphate; rapid effect via bone, kidney, gut

• Adrenal cortex → cortisol (glucocorticoid), aldosterone (mineralocorticoid), adrenal medulla → catecholamines.

• Tip: Insulin ↑ glucose uptake in muscle/fat; glucagon ↑ glucose release from liver

6. Neurophysiology

• Resting membrane potential ~ -70 mV; action potential triggered by Na+ influx.

• Synaptic transmission → chemical (neurotransmitters) or electrical (gap junctions).

• High-yield: Myasthenia gravis → antibodies against ACh receptors; Lambert-Eaton → presynaptic Ca2+ channels

• Autonomic nervous system: sympathetic (fight/flight), parasympathetic (rest/digest).

• Tip: Reflex arc → receptor → afferent neuron → CNS → efferent neuron → effector

7. High-Yield Repeated Points (NEET MDS)

• Starling’s law → stroke volume ↑ with preload

• O2 dissociation curve → right shift aids O2 delivery

• ADH → water reabsorption via aquaporins

• Intrinsic factor → B12 absorption

• Insulin → glucose uptake; glucagon → glucose release

• Resting membrane potential ~ -70 mV; AP via Na+ influx

• RAAS system → BP regulation