Basic principles and uses of UV – Spectrophotometer   The Beer-Lambert law states that absorbance is directly proportional to: (a) Wavelength of light (b) Path length and concentration (c) Temperature of the sample (d) Width of the cuvette Answer: (b) Path length and concentration Explanation: A=ϵbc, where ϵ = molar absorptivity, b = path length (cm), c = concentration (mol/L). Which component of a UV-spectrophotometer isolates specific wavelengths? (a) Photomultiplier tube (b) Monochromator (c) Cuvette (d) Deuterium lamp Answer: (b) Monochromator Explanation: The monochromator (grating/prism) selects narrow wavelength bands from…

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Physiological changes in extreme environment: Hot, Cold, Hypobaric and Hyperbaric conditions.   In hypobaric conditions (high altitude), what is the primary trigger for increased ventilation? (a) Hypocapnia (b) Hyperoxia (c) Hypoxia (d) Alkalosis Answer: (c) Explanation: Hypoxia (low oxygen) at high altitude stimulates peripheral chemoreceptors, increasing ventilation (hyperventilation). Which physiological adaptation is CRITICAL for cold acclimatization? (a) Reduced basal metabolic rate (b) Non-shivering thermogenesis (c) Peripheral vasodilation (d) Decreased subcutaneous fat Answer: (b) Explanation: Non-shivering thermogenesis via brown adipose tissue generates heat without muscle contraction, crucial for cold adaptation. Hyperbaric…

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Structure of skin   Which layer of the skin contains sweat glands and blood vessels involved in thermoregulation? (a) Epidermis (b) Hypodermis (c) Dermis (d) Stratum corneum Answer: (c) Dermis Explanation: The dermis houses sweat glands (for evaporative cooling) and blood vessels (for vasodilation/vasoconstriction), key to thermoregulation. During vasoconstriction in response to cold, blood vessels in the skin: (a) Dilate to increase heat loss (b) Constrict to reduce heat loss (c) Release sweat (d) Trigger piloerection Answer: (b) Constrict to reduce heat loss Explanation: Vasoconstriction narrows blood vessels, minimizing blood…

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Maximum aerobic power and factors affecting it.   Maximum aerobic power (VO₂ max) is defined as: (a) Maximum heart rate during exercise (b) Maximum oxygen consumption per minute during exhaustive exercise (c) Maximum carbon dioxide production during exercise (d) Maximum lactate threshold during running Answer: (b) Maximum oxygen consumption per minute during exhaustive exercise Explanation: VO₂ max is the maximum volume of oxygen (in mL/kg/min) the body can utilize during intense exercise. It’s the gold standard for measuring aerobic capacity. Which factor is the PRIMARY determinant of VO₂ max? (a)…

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Hormonal control of ovulation.   The LH surge triggering ovulation is caused by: (a) High progesterone levels (b) Sustained high estrogen levels (c) Low inhibin-B (d) FSH dominance Answer: (b) Sustained high estrogen levels Explanation: Estrogen from the dominant follicle exerts positive feedback on the pituitary at mid-cycle, causing the LH surge (≥200 pg/ml for 50 hours). Which hormone directly stimulates the rupture of the Graafian follicle? (a) Progesterone (b) Estradiol (c) Luteinizing Hormone (LH) (d) Follicle-Stimulating Hormone (FSH) Answer: (c) Luteinizing Hormone (LH) Explanation: The LH surge induces enzymatic…

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Physiological functions of the hormones – pituitary   Which hormone stimulates cortisol secretion from the adrenal cortex? (a) TSH (b) ACTH (c) FSH (d) LH Answer: (b) ACTH Explanation: ACTH (Adrenocorticotropic hormone) from the anterior pituitary triggers glucocorticoid synthesis in the adrenal zona fasciculata. Oxytocin’s primary physiological function is: (a) Milk synthesis (b) Uterine contraction (c) Bone growth (d) Thyroid regulation Answer: (b) Uterine contraction Explanation: Oxytocin (from the posterior pituitary) stimulates myometrial contractions during labor and milk ejection. Prolactin handles milk synthesis. Diabetes insipidus results from deficiency of: (a)…

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Histological structure of nephron and filtering membrane, glomerular filtration, counter current exchanger and multiplier. Physiological mechanism of tubular reabsorption and secretion. Diuresis. JG apparatus.   The glomerular filtration barrier’s size selectivity is primarily due to: (a) Podocyte foot processes (b) Basement membrane collagen IV mesh (c) Fenestrated endothelium (d) Slit diaphragm nephrin Answer: (b) Basement membrane collagen IV mesh Explanation: Basement membrane (BM) pores (5–10 nm) block molecules >70 kDa (e.g., albumin). Fenestrations allow passage but BM is key size barrier. In tubuloglomerular feedback, macula densa detects: (a) Low pH…

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Receptors as biological transducer, Muller’s law of specific nerve energies,   What is the primary function of sensory receptors? (a) Transmit neurotransmitters (b) Amplify nerve impulses (c) Convert stimuli into electrical signals (d) Produce hormones Answer: (c) Convert stimuli into electrical signals Explanation: Receptors act as biological transducers, converting external stimuli (e.g., light, sound) into electrochemical signals for neural processing. Müller’s law of specific nerve energies states that: (a) All nerves transmit identical signals (b) Sensation depends on the pathway stimulated, not the stimulus (c) Receptors adapt to constant stimuli…

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The primary sensory receptor for stretch reflex is: (a) Golgi tendon organ (b) Pacinian corpuscle (c) Muscle spindle (d) Free nerve ending Answer: (c) Muscle spindle Explanation: Muscle spindles detect muscle length changes, initiating monosynaptic stretch reflexes (e.g., knee jerk). Inverse myotatic reflex prevents muscle damage by: (a) Inhibiting antagonistic muscles (b) Activating Golgi tendon organs (c) Recruiting γ-motoneurons (d) Facilitating spindle activity Answer: (b) Activating Golgi tendon organs Explanation: Golgi tendon organs detect excessive tension, triggering inhibitory reflexes to avoid tears. Spinal shock involves: (a) Hyperreflexia below lesion (b)…

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Molecular mechanism of contraction and relaxation of different types of muscles, Sarcotubular system and excitation – contraction coupling.   Which protein covers myosin-binding sites on actin at rest? (a) Tropomyosin (b) Troponin-C (c) Titin (d) Nebulin Answer: (a) Explanation: Tropomyosin blocks actin’s myosin-binding sites; Ca²⁺-troponin complex moves it. In skeletal muscle, Ca²⁺ binds to: (a) Troponin-I (b) Troponin-T (c) Troponin-C (d) Calmodulin Answer: (c) Explanation: Troponin-C is the Ca²⁺-binding subunit initiating contraction. Dihydropyridine receptors (DHPR) function as: (a) Ca²⁺ channels in SR (b) Voltage sensors in T-tubules (c) ATP-dependent pumps…

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