NEET PG Physiology Syllabus

What does each ECG wave/interval represent: P wave, QRS complex, T wave, PR interval, QT interval?

P wave = atrial depolarization; QRS = ventricular depolarization (atrial repolarization is hidden); T wave = ventricular repolarization; PR interval = atrial depolarization plus AV nodal delay; QT interval = total ventricular depolarization and repolarization.

What ionic mechanism produces the SA node pacemaker potential (phase 4 slow depolarization)?

The 'funny' current (I_f, Na+ influx through HCN channels) plus T-type and L-type Ca2+ influx and decaying K+ efflux drive the spontaneous diastolic depolarization to threshold.

Write the equation for mean arterial pressure (MAP) and the equation relating MAP to cardiac output.

MAP = diastolic BP + 1/3 (pulse pressure) = DBP + 1/3(SBP - DBP). Also MAP = cardiac output x total peripheral resistance.

Describe the baroreceptor reflex response to a fall in blood pressure.

Reduced stretch of carotid sinus and aortic arch baroreceptors decreases afferent firing, which increases sympathetic and decreases parasympathetic output, raising heart rate, contractility, and vasoconstriction to restore BP.

Which nerves carry baroreceptor afferents from the carotid sinus and aortic arch?

Carotid sinus afferents travel via the glossopharyngeal nerve (CN IX, Hering's nerve); aortic arch afferents travel via the vagus nerve (CN X), both projecting to the nucleus tractus solitarius.

Define tidal volume, inspiratory reserve volume, expiratory reserve volume, and residual volume.

Tidal volume (~500 mL): air per normal breath. IRV (~3000 mL): extra air inhaled beyond tidal. ERV (~1100 mL): extra air exhaled beyond tidal. Residual volume (~1200 mL): air remaining after maximal expiration.

Define functional residual capacity, vital capacity, and total lung capacity in terms of volumes.

FRC = ERV + RV (air left after normal expiration). Vital capacity = IRV + TV + ERV (max air expelled after max inspiration). Total lung capacity = VC + RV (all volumes).

What is pulmonary surfactant, where is it produced, and what is its function?

Surfactant is a phospholipid (mainly dipalmitoylphosphatidylcholine) produced by type II alveolar cells; it lowers alveolar surface tension, increases compliance, prevents alveolar collapse, and stabilizes alveoli of different sizes (Laplace's law).

Give the partial pressures of O2 and CO2 in alveolar air, arterial blood, and mixed venous blood.

Alveolar: PO2 ~100 mmHg, PCO2 ~40 mmHg. Arterial: PO2 ~95-100 mmHg, PCO2 ~40 mmHg. Mixed venous: PO2 ~40 mmHg, PCO2 ~46 mmHg.

Describe the shape of the oxygen-hemoglobin dissociation curve and the physiological significance of its sigmoid form.

It is sigmoidal due to cooperative binding; the flat upper portion ensures near-full saturation despite moderate falls in alveolar PO2, while the steep lower portion allows large O2 unloading to tissues with small PO2 drops.

What is the P50 of the oxygen-hemoglobin dissociation curve, and list factors that shift the curve to the right.

P50 (~27 mmHg) is the PO2 at 50% Hb saturation. A right shift (decreased affinity, more unloading) is caused by increased CO2, increased H+ (decreased pH), increased temperature, and increased 2,3-BPG (Bohr effect).

Name the three forms in which CO2 is transported in blood and the most important one.

As bicarbonate (HCO3-, ~70%, the major form), bound to hemoglobin as carbaminohemoglobin (~23%), and dissolved in plasma (~7%).

Classify the four types of hypoxia with one example of each.

Hypoxic hypoxia (low PaO2, e.g., high altitude/lung disease); anemic hypoxia (low O2-carrying capacity, e.g., anemia/CO poisoning); stagnant/ischemic hypoxia (low blood flow, e.g., shock); histotoxic hypoxia (tissues cannot use O2, e.g., cyanide poisoning).

What is cyanosis and what minimum level of deoxygenated hemoglobin is required for it to be clinically visible?

Cyanosis is bluish discoloration of skin/mucosa from excess deoxygenated hemoglobin; it becomes visible when reduced (deoxygenated) Hb exceeds about 5 g/dL in capillary blood.

Differentiate type I and type II respiratory failure by blood gases.

Type I (hypoxemic): low PaO2 (<60 mmHg) with normal or low PaCO2 (ventilation-perfusion mismatch). Type II (hypercapnic): low PaO2 with raised PaCO2 (>50 mmHg) due to alveolar hypoventilation.

Write the formula for glomerular filtration rate (GFR) using clearance and give the marker used to measure it.

GFR = clearance of inulin = (U_inulin x V)/P_inulin, where U/P are urine/plasma concentrations and V is urine flow rate. Inulin is the gold standard (freely filtered, not reabsorbed or secreted); creatinine clearance is the clinical estimate.

State the net filtration pressure equation across the glomerulus.

Net filtration pressure = P_GC - (P_BC + pi_GC), i.e., glomerular capillary hydrostatic pressure minus the sum of Bowman's capsule hydrostatic pressure and glomerular capillary oncotic pressure (normally ~ +10 mmHg).

Where in the nephron is most filtered sodium and water reabsorbed, and how much?

The proximal convoluted tubule reabsorbs about 65-67% of filtered Na+ and water (isosmotically), along with virtually all glucose and amino acids via Na+-coupled secondary active transport.

What is the transport maximum for glucose and the renal threshold, and why does glucosuria occur in diabetes?

The tubular maximum (Tm) for glucose is ~375 mg/min and the renal threshold is ~180 mg/dL plasma glucose; when plasma glucose exceeds the threshold, SGLT carriers saturate and glucose appears in urine (glucosuria).

Write the Henderson-Hasselbalch equation for the bicarbonate buffer system and the normal arterial values.

pH = 6.1 + log10([HCO3-]/(0.03 x PCO2)). Normal arterial pH 7.35-7.45, HCO3- ~24 mEq/L, PCO2 ~40 mmHg.

How do the kidneys regulate acid-base balance?

By reabsorbing filtered HCO3- (mainly in the proximal tubule via H+ secretion and carbonic anhydrase) and generating new HCO3- through excretion of H+ buffered as titratable acid (phosphate) and ammonium (NH4+) in the collecting duct.

Classify the four primary acid-base disorders by pH, HCO3-, and PCO2.

Metabolic acidosis: low pH, low HCO3-. Metabolic alkalosis: high pH, high HCO3-. Respiratory acidosis: low pH, high PCO2. Respiratory alkalosis: high pH, low PCO2 (each with appropriate compensation).

List the major GI secretions with their key components and functions.

Saliva (amylase, lubrication); gastric juice (HCl from parietal cells, pepsinogen from chief cells, intrinsic factor); pancreatic juice (bicarbonate plus amylase, lipase, trypsinogen); bile (bile salts, emulsify fat); intestinal/brush-border enzymes (final digestion).

Name the four phases/patterns controlling GI motility and the main slow-wave pacemaker.

Gastric phases of secretion are cephalic, gastric, and intestinal; the migrating motor complex (MMC) clears the gut between meals. Slow waves originate from the interstitial cells of Cajal, the GI pacemaker.

Match these GI hormones to their main actions: gastrin, secretin, CCK.

Gastrin (G cells): stimulates gastric acid secretion and growth. Secretin (S cells): stimulates pancreatic/biliary bicarbonate, inhibits acid. CCK (I cells): stimulates pancreatic enzyme secretion and gallbladder contraction, slows gastric emptying.

Describe the hypothalamo-pituitary-thyroid axis and its feedback control.

Hypothalamic TRH stimulates anterior pituitary TSH, which stimulates thyroid release of T3/T4; T3/T4 exert negative feedback on both the pituitary (TSH) and hypothalamus (TRH).

Which hormones are secreted by the posterior pituitary, where are they made, and what do they do?

ADH (vasopressin) and oxytocin are synthesized in the hypothalamic supraoptic and paraventricular nuclei and stored/released from the posterior pituitary; ADH conserves water and constricts vessels, oxytocin causes uterine contraction and milk ejection.

Compare the actions of thyroid hormone, cortisol, and insulin on metabolism.

Thyroid hormone increases basal metabolic rate and overall metabolism; cortisol is catabolic, raising blood glucose via gluconeogenesis and protein/fat breakdown; insulin is anabolic, lowering blood glucose by promoting glucose uptake, glycogenesis, and lipogenesis.

Name the three zones of the adrenal cortex and their principal hormone products.

Zona glomerulosa -> mineralocorticoids (aldosterone); zona fasciculata -> glucocorticoids (cortisol); zona reticularis -> androgens (DHEA). The adrenal medulla secretes catecholamines (epinephrine/norepinephrine).

Distinguish the dorsal column-medial lemniscus pathway from the spinothalamic tract.

Dorsal column-medial lemniscus carries fine touch, vibration, and proprioception, decussating in the medulla. The spinothalamic (anterolateral) tract carries pain and temperature, decussating within 1-2 segments in the spinal cord.

Where does the corticospinal (pyramidal) tract decussate, and what does a lesion above versus below it produce?

About 85-90% of fibers decussate at the pyramidal decussation in the lower medulla (lateral corticospinal tract). Lesions cause contralateral upper motor neuron weakness (spasticity, hyperreflexia, Babinski sign).

Compare upper motor neuron and lower motor neuron lesion signs.

Upper motor neuron lesion: spasticity, hyperreflexia, positive Babinski, no significant atrophy, no fasciculations. Lower motor neuron lesion: flaccid paralysis, hyporeflexia, marked atrophy, and fasciculations.

Describe the stretch (myotatic) reflex and identify it as mono- or polysynaptic.

Muscle stretch activates Ia afferents from muscle spindles, which synapse directly on alpha motor neurons causing the same muscle to contract; it is a monosynaptic reflex (e.g., knee-jerk).

What are the main functions of the cerebellum and the typical signs of cerebellar dysfunction?

The cerebellum coordinates movement, balance, and motor learning; lesions cause ipsilateral ataxia, intention tremor, dysmetria, dysdiadochokinesia, nystagmus, and hypotonia.

Outline the direct and indirect pathways of the basal ganglia and their net effect on movement.

Direct pathway (via D1 receptors) disinhibits the thalamus and facilitates movement; indirect pathway (via D2 receptors) inhibits the thalamus and suppresses movement. Dopamine from the substantia nigra promotes movement by activating the direct and inhibiting the indirect pathway.

Contrast the parasympathetic and sympathetic divisions of the autonomic nervous system by outflow and ganglion location.

Sympathetic: thoracolumbar (T1-L2/3) outflow with short preganglionic and long postganglionic fibers (ganglia near the cord). Parasympathetic: craniosacral outflow (CN III, VII, IX, X and S2-S4) with long preganglionic and short postganglionic fibers (ganglia near/in target organs).

Identify the neurotransmitters and receptors at autonomic ganglia and effector organs.

All preganglionic fibers release ACh acting on nicotinic receptors. Parasympathetic postganglionic fibers release ACh on muscarinic receptors; sympathetic postganglionic fibers release norepinephrine on adrenergic receptors (except sweat glands, which use ACh).

Explain the focusing of light in the eye and which structure provides most refractive power.

Light is refracted by the cornea (which provides about two-thirds of total refractive power) and fine-focused by the lens, which changes shape during accommodation; the image is focused on the retina (fovea for sharpest vision).

What are rods and cones, and which photopigment is found in rods?

Rods provide high-sensitivity, low-resolution, monochromatic (scotopic/night) vision and contain rhodopsin; cones provide high-resolution color (photopic) vision via three opsins (red, green, blue) and are concentrated at the fovea.

Describe how the cochlea performs frequency discrimination (place theory).

The basilar membrane is tonotopically organized: high-frequency sounds maximally vibrate the stiff, narrow base near the oval window, while low-frequency sounds vibrate the wider, floppier apex; hair cells at the point of maximal displacement signal that frequency.

How do the semicircular canals and otolith organs sense head movement?

The three semicircular canals detect angular (rotational) acceleration via endolymph movement bending the cupula; the otolith organs (utricle and saccule) detect linear acceleration and head position relative to gravity via otoliths on the macula.

List the EEG rhythms with their frequency ranges and associated states.

Beta (>13 Hz, alert/active thinking), alpha (8-13 Hz, awake relaxed eyes closed), theta (4-7 Hz, drowsiness/light sleep/children), and delta (<4 Hz, deep slow-wave sleep).

Compare REM and non-REM (slow-wave) sleep.

NREM (slow-wave) sleep shows delta EEG, reduced muscle tone, and is restorative. REM sleep shows a low-voltage fast (desynchronized, awake-like) EEG, rapid eye movements, vivid dreaming, and skeletal muscle atonia (paradoxical sleep).