DNB CET Physiology Flashcards

24 sample cards from the Physiology deck

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

1. Which hormones are released from the posterior pituitary and where are they synthesized?

   ADH (vasopressin) and oxytocin are released from the posterior pituitary but synthesized in the hypothalamus (supraoptic and paraventricular nuclei) and transported down axons for storage and release.

2. Compare the actions of T3/T4 (thyroid hormones) on metabolism.

   Thyroid hormones increase basal metabolic rate, O2 consumption, heat production, carbohydrate/lipid metabolism, and potentiate catecholamine effects (increasing heart rate and contractility). They are essential for normal growth and CNS development.

3. List the hormone layers of the adrenal cortex and their main products (with mnemonic).

   Zona Glomerulosa -> mineralocorticoids (aldosterone); Zona Fasciculata -> glucocorticoids (cortisol); Zona Reticularis -> androgens (DHEA). Mnemonic: GFR / Salt, Sugar, Sex (deeper = sweeter/saltier outside).

4. Contrast the actions of insulin and glucagon on blood glucose.

   Insulin (beta cells) lowers blood glucose by promoting glucose uptake (GLUT4), glycogenesis, lipogenesis, and protein synthesis. Glucagon (alpha cells) raises blood glucose via glycogenolysis and gluconeogenesis in the liver.

5. Define temporal and spatial summation at synapses.

   Temporal summation: rapid successive impulses from one presynaptic neuron add up to reach threshold. Spatial summation: simultaneous inputs from multiple presynaptic neurons add up to reach threshold.

6. Differentiate EPSPs from IPSPs.

   EPSP (excitatory postsynaptic potential) is a depolarization that moves the membrane toward threshold (e.g., Na+ influx). IPSP (inhibitory postsynaptic potential) is a hyperpolarization that moves it away from threshold (e.g., Cl- influx or K+ efflux).

7. Describe the components of a monosynaptic stretch (myotatic) reflex arc.

   Muscle spindle (receptor) -> Ia afferent neuron -> single synapse in spinal cord -> alpha motor neuron (efferent) -> extrafusal muscle fibers (effector), causing contraction of the stretched muscle. Example: knee-jerk reflex.

8. What is reciprocal innervation in reflexes?

   When a stretch reflex activates a muscle, an inhibitory interneuron simultaneously inhibits the antagonist muscle's motor neuron, allowing coordinated movement (the agonist contracts while the antagonist relaxes).

9. Trace the visual pathway from retina to visual cortex.

   Retinal ganglion cells -> optic nerve -> optic chiasm (nasal fibers cross) -> optic tract -> lateral geniculate nucleus of thalamus -> optic radiations -> primary visual cortex (occipital lobe, area V1).

10. Explain phototransduction in rods.

    In darkness, cGMP keeps Na+ channels open (depolarized, glutamate released). Light isomerizes rhodopsin (11-cis to all-trans retinal) -> activates transducin -> activates phosphodiesterase -> cGMP breaks down -> Na+ channels close -> hyperpolarization -> decreased glutamate release.

11. Compare rods and cones.

    Rods: high sensitivity, function in dim light (scotopic), no color vision, more numerous, concentrated peripherally, contain rhodopsin. Cones: lower sensitivity, function in bright light (photopic), provide color vision and high acuity, concentrated in the fovea, three opsin types (red/green/blue).

12. How does the cochlea perform frequency (pitch) discrimination?

    By tonotopic organization of the basilar membrane (place theory): the base (stiff, narrow) responds to high frequencies and the apex (floppy, wide) responds to low frequencies. Hair cells at different positions are maximally stimulated by specific frequencies.

13. Describe auditory transduction by cochlear hair cells.

    Sound vibrates the basilar membrane, bending stereocilia against the tectorial membrane. Tip-link tension opens mechanoelectrical K+ channels -> K+ influx (from endolymph) depolarizes the hair cell -> Ca2+ entry -> neurotransmitter release onto auditory (cochlear) nerve fibers.

14. What do the semicircular canals and the otolith organs (utricle/saccule) detect?

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

15. Contrast the sympathetic and parasympathetic divisions of the ANS by outflow and ganglia location.

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

16. What neurotransmitters and receptors are used at autonomic synapses?

    All preganglionic neurons release ACh acting on nicotinic receptors. Parasympathetic postganglionic neurons release ACh on muscarinic receptors. Most sympathetic postganglionic neurons release norepinephrine on adrenergic receptors (exception: sweat glands use ACh on muscarinic receptors).

17. List the major effects of sympathetic activation (fight-or-flight).

    Increased heart rate and contractility, bronchodilation, pupil dilation (mydriasis), decreased GI motility, glycogenolysis/lipolysis, sweating, and vasoconstriction in skin/gut with vasodilation in skeletal muscle.

18. Describe the EEG waveforms and their associated states.

    Beta (>13 Hz): alert, awake, active mental activity. Alpha (8-13 Hz): awake, relaxed, eyes closed. Theta (4-7 Hz): drowsiness, light sleep, children. Delta (<4 Hz): deep sleep (slow-wave sleep).

19. Contrast REM and non-REM (NREM) sleep.

    NREM (slow-wave) sleep has delta waves, decreased muscle tone, and is restorative. REM sleep shows EEG resembling wakefulness (desynchronized, beta-like), vivid dreaming, rapid eye movements, and skeletal muscle atonia (paralysis). REM episodes lengthen toward morning.

20. What is the role of the muscle spindle versus the Golgi tendon organ?

    Muscle spindle detects muscle length and rate of stretch (afferent Ia/II), mediating the stretch reflex. Golgi tendon organ detects muscle tension/force (afferent Ib), mediating the inverse stretch reflex that inhibits the muscle to protect against excessive force.

21. State Laplace's law as applied to alveoli and its physiological significance.

    P = 2T/r (for a sphere/alveolus, T = surface tension, r = radius). Smaller alveoli have higher collapsing pressure; surfactant reduces T more in small alveoli, equalizing pressures and preventing collapse of smaller alveoli into larger ones.

22. Define the oxygen-hemoglobin dissociation curve and factors that shift it to the right.

    It is a sigmoid curve relating PO2 to hemoglobin O2 saturation. A right shift (decreased O2 affinity, easier unloading) is caused by increased CO2, increased H+ (low pH), increased temperature, and increased 2,3-DPG.

23. What is the countercurrent multiplier mechanism in the kidney?

    The loop of Henle establishes a medullary osmotic gradient: the thick ascending limb actively pumps out NaCl (impermeable to water), while the descending limb is permeable to water. This multiplied gradient enables ADH-dependent water reabsorption and concentrated urine production.

24. How does antidiuretic hormone (ADH) regulate water balance?

    ADH (vasopressin), released from the posterior pituitary in response to high plasma osmolality or low blood volume, increases water permeability of the collecting duct by inserting aquaporin-2 channels, increasing water reabsorption and producing concentrated urine.

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