NET/SLET MCQs: Life Science (Physiology)
Table of Contents
Introduction (NET/SLET)
Preparing for the CSIR-UGC NET Life Sciences Exam requires a strong understanding of Physiology, one of the most conceptual and high-weightage areas in the syllabus. To help aspirants practice effectively, we have compiled 50 advanced Physiology MCQs with answers and explanations, covering topics such as neurophysiology, cardiovascular dynamics, respiratory mechanisms, renal regulation, endocrinology, and cellular physiology.
These questions are framed in a challenging, exam-oriented pattern to help candidates test their analytical thinking, improve accuracy, and build confidence. Solving such advanced MCQs will not only strengthen your grasp of fundamental concepts but also sharpen your ability to tackle tricky questions in NET 2025 and similar competitive exams (ICMR-JRF, GATE, DBT-BET, ARS-NET).
Use this practice set as a self-assessment tool to identify weak areas, enhance time management, and simulate a real exam experience.
These MCQs are created only for educational and practice purposes. While utmost care has been taken to provide accurate answers and explanations, the questions are not taken from official CSIR-UGC NET papers. Candidates should use them as a supplementary resource alongside standard reference books (Guyton & Hall, Ganong, Alberts, Lehninger) and official NET study material.
NET Life Science (Physiology) Advanced MCQs (NET/SLET)
1. Which ion channel drives the rapid depolarization phase of the cardiac action potential?
A. Calcium channels
B. Potassium channels
C. Sodium channels
D. Chloride channels
Answer: C. Sodium channels
Explanation: The rapid depolarization (Phase 0) in ventricular myocytes is driven by the opening of voltage-gated sodium channels, allowing a fast Na⁺ influx.
2. How does antidiuretic hormone (ADH) increase water reabsorption in the kidneys?
A. Increases sodium reabsorption
B. Inserts aquaporin-2 channels in the collecting duct
C. Stimulates chloride transport
D. Inhibits potassium excretion
Answer: B. Inserts aquaporin-2 channels in the collecting duct
Explanation: ADH binds to V2 receptors, activating cAMP signaling to insert aquaporin-2 channels into the collecting duct’s apical membrane, enhancing water reabsorption.
3. Which second messenger activates protein kinase C in angiotensin II signaling?
A. Cyclic AMP (cAMP)
B. Cyclic GMP (cGMP)
C. Inositol trisphosphate (IP3)
D. Diacylglycerol (DAG)
Answer: D. Diacylglycerol (DAG)
Explanation: Angiotensin II stimulates phospholipase C, producing IP3 and DAG. DAG activates protein kinase C, while IP3 mobilizes intracellular calcium.
4. What is the role of NMDA receptors in long-term potentiation (LTP)?
A. Inhibiting calcium influx
B. Facilitating sodium efflux
C. Allowing calcium influx upon depolarization
D. Blocking potassium channels
Answer: C. Allowing calcium influx upon depolarization
Explanation: NMDA receptors, being voltage- and ligand-gated, allow Ca²⁺ influx when depolarization removes the Mg²⁺ block, triggering signaling cascades for LTP.
5. How does the sodium-potassium ATPase contribute to the resting membrane potential?
A. Directly generates action potentials
B. Maintains ion gradients across the membrane
C. Facilitates neurotransmitter release
D. Regulates calcium signaling
Answer: B. Maintains ion gradients across the membrane
Explanation: The Na⁺/K⁺ ATPase pumps 3 Na⁺ out and 2 K⁺ in, maintaining electrochemical gradients that establish the negative resting membrane potential (~-70 mV).
6. What is the primary physiological consequence of a mutation in the CFTR channel in the lungs?
A. Increased sodium reabsorption
B. Impaired chloride secretion
C. Enhanced mucus clearance
D. Increased potassium efflux
Answer: B. Impaired chloride secretion
Explanation: CFTR mutations impair Cl⁻ secretion, leading to thick mucus accumulation in the lungs, characteristic of cystic fibrosis.
7. Which hormone directly stimulates fatty acid mobilization from adipose tissue during fasting?
A. Insulin
B. Glucagon
C. Cortisol
D. Thyroxine
Answer: B. Glucagon
Explanation: Glucagon activates hormone-sensitive lipase via cAMP, promoting lipolysis and fatty acid release. Cortisol has a permissive role but is not primary.
8. What does the T wave represent in an electrocardiogram (ECG)?
A. Atrial depolarization
B. Ventricular depolarization
C. Ventricular repolarization
D. Atrial repolarization
Answer: C. Ventricular repolarization
Explanation: The T wave reflects ventricular repolarization, as potassium channels open to restore the resting membrane potential post-contraction.
9. Which signaling pathway is primarily activated by erythropoietin in erythroid progenitor cells?
A. JAK-STAT pathway
B. MAPK/ERK pathway
C. PI3K-Akt pathway
D. NF-κB pathway
Answer: A. JAK-STAT pathway
Explanation: Erythropoietin binds to its receptor, activating JAK2, which phosphorylates STAT5, promoting erythroid cell proliferation and differentiation.
10. What is the primary role of the macula densa in renal physiology?
A. Filtration of plasma
B. Sensing sodium chloride levels
C. Secretion of erythropoietin
D. Reabsorption of glucose
Answer: B. Sensing sodium chloride levels
Explanation: The macula densa in the distal tubule senses NaCl levels, regulating renin release and glomerular filtration rate via tubuloglomerular feedback.
11. Which neurotransmitter is primarily responsible for inhibitory synaptic transmission in the spinal cord?
A. Glutamate
B. Glycine
C. Acetylcholine
D. Dopamine
Answer: B. Glycine
Explanation: Glycine acts as the primary inhibitory neurotransmitter in the spinal cord, hyperpolarizing neurons via chloride influx.
12. What is the effect of increased sympathetic activity on the sinoatrial (SA) node?
A. Decreases heart rate
B. Increases pacemaker potential slope
C. Inhibits calcium influx
D. Reduces contractility
Answer: B. Increases pacemaker potential slope
Explanation: Sympathetic stimulation via norepinephrine increases the slope of the pacemaker potential in SA node cells, accelerating heart rate.
13. Which enzyme is critical for the synthesis of nitric oxide in endothelial cells?
A. Cyclooxygenase
B. Nitric oxide synthase
C. Phospholipase A2
D. Adenylyl cyclase
Answer: B. Nitric oxide synthase
Explanation: Endothelial nitric oxide synthase (eNOS) produces nitric oxide, which promotes vasodilation by relaxing smooth muscle.
14. What is the primary source of energy for cardiac muscle under anaerobic conditions?
A. Fatty acids
B. Glucose via glycolysis
C. Ketone bodies
D. Amino acids
Answer: B. Glucose via glycolysis
Explanation: Under anaerobic conditions, cardiac muscle relies on glycolysis to produce ATP, as oxidative phosphorylation is limited.
15. Which ion is primarily responsible for the plateau phase of the cardiac action potential?
A. Sodium
B. Potassium
C. Calcium
D. Chloride
Answer: C. Calcium
Explanation: The plateau phase (Phase 2) is maintained by a balance of Ca²⁺ influx through L-type calcium channels and K⁺ efflux.
16. What is the role of the Na⁺/Ca²⁺ exchanger in cardiac myocytes?
A. Initiates contraction
B. Removes calcium from the cytosol
C. Generates action potentials
D. Increases sodium influx
Answer: B. Removes calcium from the cytosol
Explanation: The Na⁺/Ca²⁺ exchanger extrudes Ca²⁺ from the cytosol post-contraction, aiding relaxation by lowering intracellular calcium.
17. Which hormone inhibits prolactin release from the anterior pituitary?
A. Thyrotropin-releasing hormone (TRH)
B. Dopamine
C. Oxytocin
D. Gonadotropin-releasing hormone (GnRH)
Answer: B. Dopamine
Explanation: Dopamine, released from the hypothalamus, inhibits prolactin secretion via D2 receptors on lactotrophs.
18. What is the primary mechanism of insulin resistance in type 2 diabetes?
A. Increased insulin receptor expression
B. Impaired insulin signaling pathways
C. Enhanced glucose uptake
D. Increased glucagon secretion
Answer: B. Impaired insulin signaling pathways
Explanation: Insulin resistance involves defective signaling, particularly in the PI3K-Akt pathway, reducing glucose transporter (GLUT4) translocation.
19. Which structure in the nephron is most affected by aldosterone?
A. Proximal convoluted tubule
B. Loop of Henle
C. Distal convoluted tubule
D. Glomerulus
Answer: C. Distal convoluted tubule
Explanation: Aldosterone enhances Na⁺ reabsorption and K⁺ secretion in the distal convoluted tubule and collecting duct via ENaC channels.
20. What is the primary trigger for the release of atrial natriuretic peptide (ANP)?
A. Low blood pressure
B. Atrial stretch
C. High plasma glucose
D. Hypoxia
Answer: B. Atrial stretch
Explanation: ANP is released from atrial myocytes in response to stretch caused by increased blood volume, promoting natriuresis and vasodilation.
21. Which receptor type is primarily involved in the fast excitatory synaptic transmission in the CNS?
A. Metabotropic glutamate receptors
B. AMPA receptors
C. GABA_A receptors
D. Dopamine D2 receptors
Answer: B. AMPA receptors
Explanation: AMPA receptors mediate fast excitatory transmission by allowing Na⁺ influx, depolarizing postsynaptic neurons.
22. What is the role of the Na⁺/H⁺ exchanger in the proximal tubule?
A. Secretes ammonia
B. Reabsorbs bicarbonate
C. Filters plasma
D. Secretes potassium
Answer: B. Reabsorbs bicarbonate
Explanation: The Na⁺/H⁺ exchanger facilitates H⁺ secretion and Na⁺ reabsorption, indirectly enabling bicarbonate reabsorption to maintain acid-base balance.
23. Which process is primarily responsible for the termination of neurotransmitter action in the synaptic cleft?
A. Diffusion
B. Enzymatic degradation
C. Reuptake by transporters
D. Receptor internalization
Answer: C. Reuptake by transporters
Explanation: Neurotransmitter reuptake by specific transporters (e.g., SERT for serotonin) is the primary mechanism for terminating synaptic signaling.
24. What is the effect of hyperkalemia on the cardiac membrane potential?
A. Hyperpolarizes the membrane
B. Depolarizes the resting membrane
C. Increases action potential duration
D. Inhibits sodium channels
Answer: B. Depolarizes the resting membrane
Explanation: Elevated extracellular K⁺ reduces the K⁺ gradient, depolarizing the resting membrane potential and potentially causing arrhythmias.
25. Which hormone enhances gluconeogenesis in the liver during stress?
A. Insulin
B. Glucagon
C. Cortisol
D. Epinephrine
Answer: C. Cortisol
Explanation: Cortisol promotes gluconeogenesis by upregulating enzymes like PEPCK, increasing glucose production during stress.
26. What is the primary function of gap junctions in cardiac muscle?
A. Mechanical contraction
B. Electrical coupling
C. Hormone secretion
D. Nutrient transport
Answer: B. Electrical coupling
Explanation: Gap junctions allow rapid transmission of action potentials between cardiac myocytes, ensuring synchronized contraction.
27. Which ion is critical for neurotransmitter release at the presynaptic terminal?
A. Sodium
B. Potassium
C. Calcium
D. Chloride
Answer: C. Calcium
Explanation: Ca²⁺ influx through voltage-gated channels triggers vesicle fusion and neurotransmitter release at the synapse.
28. What is the primary role of the countercurrent multiplier system in the Loop of Henle?
A. Glucose reabsorption
B. Urine concentration
C. Filtration of plasma
D. Secretion of toxins
Answer: B. Urine concentration
Explanation: The countercurrent multiplier creates an osmotic gradient in the medulla, enabling water reabsorption and urine concentration.
29. Which receptor mediates the effects of epinephrine in increasing heart rate?
A. Alpha-1 adrenergic
B. Beta-1 adrenergic
C. Muscarinic
D. Nicotinic
Answer: B. Beta-1 adrenergic
Explanation: Beta-1 adrenergic receptors on SA node cells mediate epinephrine’s effect, increasing cAMP and heart rate.
30. What is the primary defect in Liddle’s syndrome?
A. Decreased ENaC activity
B. Increased ENaC activity
C. Impaired CFTR function
D. Reduced aldosterone secretion
Answer: B. Increased ENaC activity
Explanation: Liddle’s syndrome involves gain-of-function mutations in ENaC, causing excessive Na⁺ reabsorption and hypertension.
31. Which signaling molecule is elevated in hypoxia to stimulate angiogenesis?
A. Nitric oxide
B. VEGF
C. Prostaglandin E2
D. Bradykinin
Answer: B. VEGF
Explanation: Hypoxia induces HIF-1α, which upregulates vascular endothelial growth factor (VEGF), promoting angiogenesis.
32. What is the role of the Na⁺/K⁺/2Cl⁻ cotransporter in the thick ascending limb?
A. Water reabsorption
B. Sodium reabsorption
C. Glucose transport
D. Calcium secretion
Answer: B. Sodium reabsorption
Explanation: The NKCC2 cotransporter reabsorbs Na⁺, K⁺, and Cl⁻, contributing to the medullary osmotic gradient for urine concentration.
33. Which hormone is critical for milk ejection during lactation?
A. Prolactin
B. Oxytocin
C. Estrogen
D. Progesterone
Answer: B. Oxytocin
Explanation: Oxytocin triggers myoepithelial cell contraction in the mammary glands, facilitating milk ejection.
34. What is the effect of parasympathetic stimulation on bronchial smooth muscle?
A. Relaxation
B. Contraction
C. No effect
D. Increased mucus secretion
Answer: B. Contraction
Explanation: Parasympathetic stimulation via acetylcholine causes bronchoconstriction, reducing airway diameter.
35. Which protein is critical for oxygen binding in skeletal muscle?
A. Hemoglobin
B. Myoglobin
C. Albumin
D. Transferrin
Answer: B. Myoglobin
Explanation: Myoglobin stores and transports oxygen in skeletal muscle, facilitating aerobic metabolism.
36. What is the primary source of ATP in red blood cells?
A. Oxidative phosphorylation
B. Glycolysis
C. Krebs cycle
D. Beta-oxidation
Answer: B. Glycolysis
Explanation: Red blood cells lack mitochondria and rely on glycolysis for ATP production.
37. Which enzyme converts angiotensin I to angiotensin II?
A. Renin
B. ACE
C. Aldosterone synthase
D. Catechol-O-methyltransferase
Answer: B. ACE
Explanation: Angiotensin-converting enzyme (ACE) cleaves angiotensin I to produce angiotensin II, a potent vasoconstrictor.
38. What is the role of the sarcoplasmic reticulum in muscle contraction?
A. Stores sodium ions
B. Releases calcium ions
C. Synthesizes ATP
D. Degrades neurotransmitters
Answer: B. Releases calcium ions
Explanation: The sarcoplasmic reticulum releases Ca²⁺ in response to an action potential, triggering muscle contraction via troponin binding.
39. Which condition results from a deficiency in 21-hydroxylase enzyme?
A. Addison’s disease
B. Congenital adrenal hyperplasia
C. Cushing’s syndrome
D. Pheochromocytoma
Answer: B. Congenital adrenal hyperplasia
Explanation: 21-hydroxylase deficiency impairs cortisol and aldosterone synthesis, leading to adrenal hyperplasia and salt-wasting.
40. What is the primary role of the baroreceptors in blood pressure regulation?
A. Sense blood glucose levels
B. Detect arterial pressure changes
C. Regulate heart contractility
D. Control venous return
Answer: B. Detect arterial pressure changes
Explanation: Baroreceptors in the carotid sinus and aortic arch detect changes in arterial pressure, modulating autonomic responses to maintain homeostasis.
41. Which ion channel is blocked by tetrodotoxin (TTX)?
A. Potassium channels
B. Calcium channels
C. Sodium channels
D. Chloride channels
Answer: C. Sodium channels
Explanation: TTX blocks voltage-gated sodium channels, preventing action potential propagation in neurons and muscles.
42. What is the primary effect of calcitonin on bone?
A. Stimulates osteoclast activity
B. Inhibits osteoclast activity
C. Increases calcium absorption
D. Promotes bone formation
Answer: B. Inhibits osteoclast activity
Explanation: Calcitonin reduces bone resorption by inhibiting osteoclasts, lowering blood calcium levels.
43. Which process is impaired in myasthenia gravis?
A. Acetylcholine synthesis
B. Neuromuscular transmission
C. Sodium channel activation
D. Calcium reuptake
Answer: B. Neuromuscular transmission
Explanation: Myasthenia gravis involves autoantibodies against nicotinic acetylcholine receptors, impairing neuromuscular transmission.
44. What is the primary role of the Na⁺/Ca²⁺ exchanger in the renal tubule?
A. Sodium reabsorption
B. Calcium reabsorption
C. Potassium secretion
D. Bicarbonate reabsorption
Answer: B. Calcium reabsorption
Explanation: The Na⁺/Ca²⁺ exchanger in the distal tubule facilitates calcium reabsorption, driven by the sodium gradient.
45. Which hormone is critical for red blood cell maturation?
A. Thyroxine
B. Erythropoietin
C. Cortisol
D. Insulin
Answer: B. Erythropoietin
Explanation: Erythropoietin stimulates erythroid progenitor cell differentiation and maturation in the bone marrow.
46. What is the effect of increased cyclic AMP in cardiac myocytes?
A. Decreases contractility
B. Increases contractility
C. Inhibits calcium release
D. Reduces heart rate
Answer: B. Increases contractility
Explanation: cAMP activates PKA, which phosphorylates calcium channels and phospholamban, enhancing calcium influx and contractility.
47. Which structure is primarily responsible for sensing linear acceleration in the inner ear?
A. Semicircular canals
B. Cochlea
C. Utricle and saccule
D. Organ of Corti
Answer: C. Utricle and saccule
Explanation: The utricle and saccule contain otoliths that detect linear acceleration and head position relative to gravity.
48. What is the primary defect in polycystic kidney disease?
A. Impaired sodium reabsorption
B. Mutations in polycystin proteins
C. Reduced glomerular filtration
D. Excessive aldosterone production
Answer: B. Mutations in polycystin proteins
Explanation: Mutations in PKD1 or PKD2 genes, encoding polycystins, disrupt renal tubular cell signaling, leading to cyst formation.
49. Which neurotransmitter is primarily involved in the reward pathway of the brain?
A. GABA
B. Glutamate
C. Dopamine
D. Serotonin
Answer: C. Dopamine
Explanation: Dopamine in the mesolimbic pathway, particularly the nucleus accumbens, mediates reward and motivation.
50. What is the primary mechanism of action of loop diuretics like furosemide?
A. Inhibits Na⁺/K⁺/2Cl⁻ cotransporter
B. Blocks ENaC channels
C. Inhibits carbonic anhydrase
D. Enhances aquaporin expression
Answer: A. Inhibits Na⁺/K⁺/2Cl⁻ cotransporter
Explanation: Loop diuretics inhibit the NKCC2 cotransporter in the thick ascending limb, reducing Na⁺ reabsorption and increasing urine output.
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