Chapter: Reproductive Physiology
Topic: Male Reproduction
Subtopic: Spermatogenesis
Keyword Definitions:
• Spermatogenesis: Process by which spermatozoa develop from spermatogonia.
• Spermiogenesis: Transformation of spermatids into spermatozoa.
• Spermatogonia: Stem cells of seminiferous tubules.
• Sertoli cells: Supporting cells aiding spermatogenesis.
• Leydig cells: Testosterone-secreting cells of testes.
• Epididymis: Site for sperm storage and maturation.
• Seminiferous tubules: Functional units where spermatogenesis occurs.
• Ductus deferens: Sperm transport tube.
• Prostate: Produces seminal fluid component.
• Acrosome: Cap of sperm head containing enzymes.
Lead Question - 2013
Spermatogenesis takes place in ?
a) Epididymis
b) Seminiferous tubule
c) Ductus deferens
d) Prostate
Explanation: Spermatogenesis, the process of sperm production, occurs inside the seminiferous tubules of testes. Sertoli cells support and nourish developing sperm, while Leydig cells produce testosterone. Epididymis stores sperm, but formation happens only in seminiferous tubules. Correct answer: b) Seminiferous tubule.
1) Which hormone is essential for initiating spermatogenesis?
a) LH
b) FSH
c) Prolactin
d) ACTH
Explanation: FSH acts on Sertoli cells to initiate spermatogenesis. LH primarily stimulates Leydig cells to produce testosterone. Together, both regulate sperm formation. Correct answer: b) FSH.
2) Clinical case: A young male with hypogonadotropic hypogonadism presents with azoospermia. Which hormone therapy will help restore spermatogenesis?
a) Prolactin
b) GH
c) FSH and LH
d) Cortisol
Explanation: Both FSH and LH are required. FSH stimulates Sertoli cells, while LH stimulates Leydig cells for testosterone. Their combination restores spermatogenesis. Correct answer: c) FSH and LH.
3) Duration of complete spermatogenesis in humans is approximately:
a) 24 hours
b) 24 days
c) 64 days
d) 120 days
Explanation: Spermatogenesis from spermatogonia to mature spermatozoa takes about 64 days. This includes mitosis, meiosis, and spermiogenesis. Correct answer: c) 64 days.
4) Clinical case: A patient with Klinefelter syndrome is infertile. Which abnormality in spermatogenesis is expected?
a) Normal spermatid formation
b) Absence of spermatogenesis
c) Increased sperm count
d) Normal motility
Explanation: Klinefelter syndrome (47,XXY) leads to seminiferous tubule fibrosis, small testes, and absent spermatogenesis, causing infertility. Correct answer: b) Absence of spermatogenesis.
5) The blood-testis barrier is formed by:
a) Leydig cells
b) Sertoli cells
c) Spermatogonia
d) Myoid cells
Explanation: Sertoli cells form tight junctions creating the blood-testis barrier, protecting developing spermatocytes from immune recognition. Correct answer: b) Sertoli cells.
6) Clinical case: A man receiving testosterone injections for bodybuilding develops infertility. The reason is:
a) Stimulation of FSH
b) Inhibition of GnRH, FSH, and LH
c) Increased Sertoli cell activity
d) Increased spermiogenesis
Explanation: Exogenous testosterone suppresses hypothalamic GnRH and pituitary FSH/LH secretion, reducing intratesticular testosterone and halting spermatogenesis. Correct answer: b) Inhibition of GnRH, FSH, and LH.
7) Which stage of spermatogenesis is haploid?
a) Spermatogonia
b) Primary spermatocyte
c) Secondary spermatocyte
d) Spermatogonia type B
Explanation: Secondary spermatocytes and spermatids are haploid, formed after meiosis I. Correct answer: c) Secondary spermatocyte.
8) Clinical case: A chemotherapy patient presents with permanent azoospermia. Which testicular cells are most sensitive to chemotherapy?
a) Spermatogonia
b) Sertoli cells
c) Leydig cells
d) Spermatozoa
Explanation: Spermatogonia are highly mitotically active and most vulnerable to chemotherapy and radiation, leading to infertility. Correct answer: a) Spermatogonia.
9) Capacitation of sperm occurs in:
a) Testis
b) Epididymis
c) Female genital tract
d) Prostate
Explanation: Capacitation, essential for fertilization, occurs in the female reproductive tract, making sperm capable of acrosome reaction. Correct answer: c) Female genital tract.
10) Clinical case: A male with immotile sperm but normal morphology and count likely has defect in:
a) Mitochondrial sheath
b) Dynein arms of flagella
c) Acrosome
d) Sertoli cell function
Explanation: Dynein arms are required for flagellar movement. Their absence causes immotile sperm syndrome (Kartagener syndrome), leading to infertility. Correct answer: b) Dynein arms of flagella.
Chapter: Endocrine Physiology
Topic: Growth Hormone
Subtopic: IGF-1 Mediated Actions
Keyword Definitions:
• Growth Hormone (GH): A peptide hormone secreted by anterior pituitary that regulates growth and metabolism.
• IGF-1 (Insulin-like Growth Factor-1): A liver-derived peptide mediating growth-promoting actions of GH.
• Lipolysis: Breakdown of stored fat into free fatty acids.
• Antilipolysis: Inhibition of fat breakdown.
• Na⁺ Retention: Reabsorption of sodium mainly under aldosterone influence.
• Insulin: Hormone lowering blood glucose by promoting uptake and storage.
• Anabolism: Process of building complex molecules from simpler ones.
• Cartilage Growth: IGF-1 stimulates chondrocytes for bone elongation.
• Somatomedins: Group of peptides like IGF-1 mediating GH effects.
• Acromegaly: GH excess disorder in adults, associated with high IGF-1.
Lead Question - 2013
Which of the following action of GH is mediated by IGF-1?
a) Lipolysis
b) decreases insulin
c) Antilipolysis
d) Na⁺ retention
Explanation: Growth hormone acts directly for metabolic effects like lipolysis and insulin antagonism. However, its growth-promoting effects such as cartilage and bone growth are mediated by IGF-1. Hence IGF-1 mediates anabolic, growth, and cell proliferation effects. Correct answer: c) Antilipolysis.
1) Which organ primarily secretes IGF-1?
a) Pancreas
b) Liver
c) Kidney
d) Thyroid
Explanation: IGF-1 is mainly secreted by the liver in response to GH stimulation. It mediates anabolic effects of GH, particularly bone and cartilage growth. Correct answer: b) Liver.
2) Clinical case: A child with short stature has low IGF-1 but normal GH. The defect is likely in:
a) Pituitary gland
b) Liver
c) Thyroid
d) Adrenal cortex
Explanation: Normal GH with low IGF-1 indicates hepatic resistance or liver dysfunction. The liver is responsible for IGF-1 synthesis. Correct answer: b) Liver.
3) Direct metabolic action of GH is:
a) Protein synthesis
b) Antilipolysis
c) Lipolysis
d) Chondrocyte stimulation
Explanation: GH directly promotes lipolysis and antagonizes insulin action. Protein synthesis and bone growth are mediated via IGF-1. Correct answer: c) Lipolysis.
4) Clinical case: An adult male with acromegaly has elevated:
a) GH only
b) IGF-1 only
c) Both GH and IGF-1
d) Cortisol
Explanation: Acromegaly results from GH excess leading to persistently elevated IGF-1, the main diagnostic marker. Correct answer: c) Both GH and IGF-1.
5) Which receptor mediates IGF-1 action?
a) G-protein coupled receptor
b) Tyrosine kinase receptor
c) Nuclear receptor
d) Ion channel receptor
Explanation: IGF-1 binds to a tyrosine kinase receptor similar to the insulin receptor, activating MAP kinase and PI3K pathways. Correct answer: b) Tyrosine kinase receptor.
6) Clinical case: A neonate with GH receptor mutation presents with short stature and low IGF-1 despite high GH. This condition is:
a) Acromegaly
b) Laron dwarfism
c) Cushing’s syndrome
d) Kallmann syndrome
Explanation: Laron dwarfism results from GH receptor defects, leading to low IGF-1 despite high GH. Correct answer: b) Laron dwarfism.
7) Which is NOT mediated by IGF-1?
a) Bone growth
b) Protein synthesis
c) Lipolysis
d) Cell proliferation
Explanation: Lipolysis is a direct action of GH, not mediated by IGF-1. Growth and protein anabolism are IGF-1 mediated. Correct answer: c) Lipolysis.
8) Clinical case: A child with GH deficiency shows delayed bone age. Which treatment normalizes growth?
a) Cortisol
b) GH therapy
c) Thyroxine
d) IGF-1 only
Explanation: Recombinant GH therapy stimulates IGF-1 production, restoring bone growth and normalizing bone age. Correct answer: b) GH therapy.
9) Half-life of IGF-1 in circulation is prolonged by binding to:
a) Albumin
b) IGF-binding proteins
c) Globulins
d) Transferrin
Explanation: IGF-1 circulates bound to IGF-binding proteins, especially IGFBP-3, which prolongs its half-life. Correct answer: b) IGF-binding proteins.
10) Clinical case: A boy treated with high-dose glucocorticoids has growth retardation because:
a) Inhibition of GH secretion
b) Inhibition of IGF-1 synthesis
c) Decreased insulin levels
d) Increased thyroid hormones
Explanation: Glucocorticoids suppress hepatic IGF-1 synthesis and impair growth despite normal GH. Correct answer: b) Inhibition of IGF-1 synthesis.
Chapter: Endocrine Physiology
Topic: Growth Hormone
Subtopic: Regulation of GH Secretion
Keyword Definitions:
• Growth Hormone (GH): Peptide hormone secreted by anterior pituitary regulating growth and metabolism.
• GHRH: Hypothalamic hormone that stimulates GH release.
• Somatostatin: Inhibits GH secretion from pituitary.
• Fasting: Stimulates GH secretion by lowering glucose.
• Exercise: Potent physiological stimulator of GH.
• Stress: Stimulates GH via catecholamine pathways.
• Free fatty acids: High levels suppress GH secretion.
• IGF-1: Provides negative feedback on GH secretion.
• Sleep: GH peaks during deep sleep.
• Acromegaly: Disorder of GH excess causing elevated IGF-1.
Lead Question - 2013
All of the following stimulate GH release, except-
a) Fasting
b) Exercise
c) Free fatty acids
d) Stress
Explanation: Growth hormone release is stimulated by fasting, exercise, stress, and hypoglycemia. However, free fatty acids act as an inhibitor of GH secretion by negative feedback. Correct answer: c) Free fatty acids.
1) Major hypothalamic stimulator of GH secretion is:
a) Dopamine
b) GHRH
c) Somatostatin
d) Vasopressin
Explanation: GHRH (Growth Hormone Releasing Hormone) from hypothalamus stimulates GH release from pituitary, while somatostatin inhibits it. Correct answer: b) GHRH.
2) Clinical case: A child with hypoglycemia during fasting has elevated GH. This rise is explained by:
a) Glucose-induced inhibition
b) Hypoglycemia stimulation
c) Free fatty acid stimulation
d) IGF-1 stimulation
Explanation: Hypoglycemia is a strong stimulus for GH secretion to mobilize energy stores. This explains elevated GH in fasting hypoglycemia. Correct answer: b) Hypoglycemia stimulation.
3) Which of the following inhibits GH secretion?
a) Dopamine
b) Somatostatin
c) GHRH
d) Stress
Explanation: Somatostatin secreted by hypothalamus directly inhibits GH release from pituitary somatotrophs. Correct answer: b) Somatostatin.
4) Clinical case: A patient with acromegaly is treated with octreotide. Its mechanism is:
a) GHRH agonist
b) Somatostatin analog
c) Dopamine antagonist
d) IGF-1 analog
Explanation: Octreotide is a somatostatin analog used to suppress GH secretion in acromegaly. Correct answer: b) Somatostatin analog.
5) During which stage of sleep is GH secretion maximum?
a) REM
b) Stage 1
c) Stage 2
d) Deep sleep (Stage 3/4)
Explanation: GH secretion peaks during slow-wave deep sleep (Stage 3/4), essential for growth and tissue repair. Correct answer: d) Deep sleep (Stage 3/4).
6) Clinical case: A boy with delayed growth has low GH response to exercise. This suggests:
a) GH deficiency
b) Hyperthyroidism
c) Cortisol excess
d) Normal physiology
Explanation: Exercise normally stimulates GH release. Lack of GH response indicates GH deficiency. Correct answer: a) GH deficiency.
7) Which of the following increases GH secretion?
a) High glucose
b) Fasting
c) Elevated free fatty acids
d) Exogenous IGF-1
Explanation: Fasting and hypoglycemia stimulate GH release, while high glucose, IGF-1, and free fatty acids inhibit secretion. Correct answer: b) Fasting.
8) Clinical case: A man with pituitary tumor secreting GH presents with diabetes. The mechanism is:
a) GH-induced insulin resistance
b) Direct insulin deficiency
c) Pancreatic destruction
d) Somatostatin excess
Explanation: GH induces insulin resistance by opposing insulin action, leading to hyperglycemia and diabetes. Correct answer: a) GH-induced insulin resistance.
9) Which neurotransmitter promotes GH secretion?
a) Norepinephrine
b) Serotonin
c) Acetylcholine
d) Dopamine
Explanation: Dopamine increases GH release, while norepinephrine and serotonin modulate hypothalamic function variably. Correct answer: d) Dopamine.
10) Clinical case: A girl treated with glucocorticoids develops growth retardation. The cause is:
a) Increased GH
b) Decreased GH
c) Suppression of IGF-1
d) Stimulation of GH secretion
Explanation: Glucocorticoids suppress GH action and reduce IGF-1 synthesis, leading to growth retardation. Correct answer: c) Suppression of IGF-1.
Chapter: Endocrine Physiology
Topic: Thyroid Hormones
Subtopic: Half-life and Metabolism of T3
Keyword Definitions:
• T3 (Triiodothyronine): Active thyroid hormone regulating metabolism.
• T4 (Thyroxine): Prohormone converted to T3 in tissues.
• Half-life: Time required for plasma concentration of a hormone to reduce by half.
• Thyroxine-binding globulin (TBG): Protein carrying thyroid hormones in blood.
• Metabolism: Biological process by which thyroid hormones are degraded.
• Hyperthyroidism: Excess thyroid hormone with increased metabolism.
• Hypothyroidism: Deficient thyroid hormone with slowed metabolism.
• Deiodinases: Enzymes that convert T4 into T3 or reverse T3.
• rT3: Inactive metabolite of T4.
• Plasma proteins: Carrier molecules affecting hormone half-life.
Lead Question - 2013
Half life of T3 ?
a) 10 hours
b) 1 day
c) 6 days
d) 10 days
Explanation: T3 is the biologically active thyroid hormone with a relatively short plasma half-life compared to T4. Its half-life is around 1 day due to weaker protein binding. Correct answer: b) 1 day.
1) Which thyroid hormone has the longer half-life?
a) T3
b) T4
c) rT3
d) None
Explanation: T4 binds more strongly to thyroxine-binding globulin and has a half-life of about 6–7 days, while T3’s half-life is only 1 day. Correct answer: b) T4.
2) Clinical case: A patient with liver disease shows reduced TBG. Effect on T3 half-life is:
a) Increased
b) Decreased
c) No change
d) Doubled
Explanation: Lower TBG reduces binding of thyroid hormones, leading to increased clearance and shorter half-life of T3. Correct answer: b) Decreased.
3) Major site of T4 to T3 conversion is:
a) Thyroid gland
b) Liver
c) Bone
d) Skin
Explanation: Liver and kidneys are primary sites for peripheral conversion of T4 to active T3 by deiodinases. Correct answer: b) Liver.
4) Clinical case: In a patient with severe illness, rT3 levels are high. The mechanism is:
a) Increased T4 to T3 conversion
b) Increased T4 to rT3 conversion
c) Decreased T3 secretion by thyroid
d) Increased TBG binding
Explanation: Illness shifts metabolism toward production of inactive rT3 instead of T3. Correct answer: b) Increased T4 to rT3 conversion.
5) Which plasma protein has the highest affinity for T3 and T4?
a) Albumin
b) Prealbumin
c) Thyroxine-binding globulin (TBG)
d) Transferrin
Explanation: TBG has the highest affinity and transports most thyroid hormone, prolonging half-life. Correct answer: c) Thyroxine-binding globulin (TBG).
6) Clinical case: A woman on oral contraceptives has increased TBG. Effect on total T3 levels?
a) Increased
b) Decreased
c) No change
d) Rapid fall
Explanation: Estrogen increases TBG levels, raising total T3 and T4, while free hormone remains normal. Correct answer: a) Increased.
7) Half-life of T4 in plasma is approximately:
a) 1 day
b) 3 days
c) 6–7 days
d) 14 days
Explanation: T4 has a long half-life of about 6–7 days, much longer than T3, due to stronger protein binding. Correct answer: c) 6–7 days.
8) Clinical case: A hypothyroid patient is started on levothyroxine (T4). Clinical improvement is seen after weeks because:
a) Rapid metabolism
b) Long half-life
c) Poor absorption
d) Deiodinase deficiency
Explanation: T4 has a long half-life of about 7 days, so steady-state levels take several weeks to achieve, delaying clinical improvement. Correct answer: b) Long half-life.
9) Which enzyme activates thyroid hormone in tissues?
a) Deiodinase I
b) Deiodinase II
c) Deiodinase III
d) Peroxidase
Explanation: Deiodinase II converts T4 into active T3 in tissues like brain and pituitary. Correct answer: b) Deiodinase II.
10) Clinical case: In renal failure, half-life of thyroid hormones is:
a) Increased
b) Decreased
c) Unchanged
d) Variable
Explanation: Reduced renal clearance and protein abnormalities prolong half-life of thyroid hormones in renal failure. Correct answer: a) Increased.
Chapter: Endocrine Physiology
Topic: Stress Hormones
Subtopic: Hormonal Response to Stress
Keyword Definitions:
• Stress: A physiological condition activating neuroendocrine responses.
• ADH: Antidiuretic hormone that conserves water during stress.
• Thyroxine: Thyroid hormone regulating metabolism, not acutely elevated in stress.
• GH: Growth hormone, rises during stress and fasting.
• Cortisol: Major stress hormone increasing glucose availability.
• Sympathetic system: Activates adrenaline and noradrenaline release.
• Allostasis: Process of maintaining stability through physiological change during stress.
• CRH: Corticotropin-releasing hormone initiating stress axis.
• ACTH: Stimulates adrenal cortisol release in stress.
• Chronic stress: Prolonged stress leading to maladaptation.
Lead Question - 2013
Not increased in stress ?
a) ADH
b) thyroxine
c) GH
d) None
Explanation: Stress activates hypothalamic-pituitary-adrenal axis, increasing ADH, GH, and cortisol. Thyroxine is not acutely elevated in stress. Thus, the hormone not increased in stress is thyroxine. Correct answer: b) thyroxine.
1) Which is the major stress hormone?
a) Cortisol
b) Insulin
c) Aldosterone
d) Calcitonin
Explanation: Cortisol is the major glucocorticoid secreted during stress. It increases blood glucose, suppresses immunity, and promotes catabolism. Correct answer: a) Cortisol.
2) Clinical case: A patient in shock has high ADH. Reason is:
a) Increased plasma volume
b) Increased plasma osmolality
c) Decreased blood pressure
d) Increased sodium
Explanation: ADH is secreted in stress states like hypovolemia and hypotension, aiding water retention. Correct answer: c) Decreased blood pressure.
3) Which hormone is secreted by the adrenal medulla during stress?
a) Cortisol
b) Aldosterone
c) Epinephrine
d) Insulin
Explanation: The adrenal medulla secretes epinephrine and norepinephrine under sympathetic stimulation during stress, causing fight-or-flight responses. Correct answer: c) Epinephrine.
4) Clinical case: In acute surgery stress, which hormone spikes?
a) Insulin
b) Cortisol
c) Calcitonin
d) TSH
Explanation: Acute surgical stress activates HPA axis, raising cortisol levels, which increase glucose and support catabolic energy supply. Correct answer: b) Cortisol.
5) Which hypothalamic hormone starts the stress response?
a) GHRH
b) CRH
c) TRH
d) GnRH
Explanation: Corticotropin-releasing hormone (CRH) from the hypothalamus activates pituitary ACTH release, initiating the stress response. Correct answer: b) CRH.
6) Clinical case: A patient with chronic stress shows immune suppression. Hormone responsible is:
a) Cortisol
b) ADH
c) GH
d) Thyroxine
Explanation: Prolonged cortisol elevation suppresses immunity and promotes protein catabolism. Correct answer: a) Cortisol.
7) Which hormone does not increase immediately in acute stress?
a) GH
b) ADH
c) Cortisol
d) Thyroxine
Explanation: Thyroxine does not acutely rise during stress; cortisol, GH, and ADH do. Correct answer: d) Thyroxine.
8) Clinical case: In stress, blood glucose rises mainly due to:
a) Insulin increase
b) Cortisol and catecholamines
c) Thyroxine
d) Aldosterone
Explanation: Stress hormones (cortisol, epinephrine) increase gluconeogenesis and glycogenolysis, raising glucose. Correct answer: b) Cortisol and catecholamines.
9) Which anterior pituitary hormone increases in stress?
a) Prolactin
b) ACTH
c) TSH
d) FSH
Explanation: ACTH increases, stimulating adrenal cortisol secretion. Correct answer: b) ACTH.
10) Clinical case: In stress, GH increases. Its role is:
a) Promotes lipolysis
b) Increases glycogen storage
c) Promotes insulin release
d) Increases calcium absorption
Explanation: Growth hormone rises in stress, promoting lipolysis and conserving glucose for vital organs. Correct answer: a) Promotes lipolysis.
Chapter: General Physiology
Topic: Body Fluid Compartments
Subtopic: Measurement of Plasma Volume
Keyword Definitions:
• Plasma volume: Volume of plasma in blood, measured using dye dilution techniques.
• Evans blue: Dye binding to plasma proteins, used to measure plasma volume.
• Inulin: Polysaccharide used for GFR measurement, not plasma volume.
• Mannitol: Used to measure extracellular fluid volume.
• D2O (Deuterium oxide): Used to measure total body water.
Lead Question - 2013
Plasma volume is measured by ?
a) Inulin
b) Evans blue
c) Mannitol
d) D2O
Explanation: Plasma volume is best measured by Evans blue dye, which binds to plasma proteins like albumin, remaining confined within the vascular compartment. Inulin is for GFR, Mannitol for ECF, and D2O for total body water. Correct answer: Evans blue.
1) Plasma osmolality is mainly determined by?
a) Sodium
b) Potassium
c) Calcium
d) Glucose
Explanation: Plasma osmolality primarily depends on sodium and its associated anions, as sodium is the major extracellular cation. Glucose and urea contribute less significantly under normal conditions. Correct answer: Sodium.
2) A patient receives IV mannitol infusion. What compartment expands most?
a) Plasma volume
b) Extracellular fluid
c) Intracellular fluid
d) Total body water
Explanation: Mannitol distributes only in extracellular fluid, not intracellular fluid. Thus, it expands ECF volume, increasing osmotic gradient and drawing water out of cells. Correct answer: Extracellular fluid.
3) Extracellular fluid volume is measured using?
a) Mannitol
b) Inulin
c) Evans blue
d) D2O
Explanation: Mannitol, sucrose, or thiosulfate can be used to measure extracellular fluid volume since they distribute in both plasma and interstitial fluid compartments but not intracellularly. Correct answer: Mannitol.
4) A patient presents with edema. Plasma volume estimation is best done by?
a) Radio-iodinated albumin
b) Inulin
c) Mannitol
d) D2O
Explanation: Plasma volume is accurately measured by dyes like Evans blue or radio-iodinated albumin, which bind plasma proteins. They do not cross into interstitial fluid. Correct answer: Radio-iodinated albumin.
5) Total body water is best measured by?
a) Inulin
b) D2O
c) Evans blue
d) Mannitol
Explanation: Deuterium oxide (D2O) or tritiated water distributes throughout all compartments, making them ideal for total body water measurement. Correct answer: D2O.
6) A child with diarrhea and dehydration is admitted. Which compartment is lost most?
a) Plasma volume
b) Interstitial fluid
c) Intracellular fluid
d) Extracellular fluid
Explanation: Diarrhea causes loss of extracellular fluid (plasma + interstitial fluid). Severe dehydration may later involve intracellular fluid. Correct answer: Extracellular fluid.
7) Interstitial fluid volume is calculated as?
a) Total body water – Plasma volume
b) Extracellular fluid – Plasma volume
c) Intracellular fluid – Plasma volume
d) Plasma volume – ECF
Explanation: Interstitial fluid cannot be measured directly but is calculated as extracellular fluid volume minus plasma volume. Correct answer: Extracellular fluid – Plasma volume.
8) A burn patient develops hypovolemia. Which compartment is primarily lost?
a) Intracellular fluid
b) Plasma volume
c) Interstitial fluid
d) Extracellular fluid
Explanation: Burns cause increased capillary permeability, leading to plasma protein and fluid loss into interstitial space, reducing plasma volume and overall ECF. Correct answer: Plasma volume.
9) Inulin clearance is used to measure?
a) Plasma volume
b) GFR
c) ECF volume
d) Total body water
Explanation: Inulin is freely filtered by glomeruli, not reabsorbed or secreted. Its clearance accurately measures glomerular filtration rate (GFR), not body fluid compartments. Correct answer: GFR.
10) A 65-year-old hypertensive patient on diuretics shows hyponatremia. Which compartment shrinks most?
a) Intracellular fluid
b) Extracellular fluid
c) Plasma volume
d) Interstitial fluid
Explanation: Diuretic use with sodium loss primarily reduces extracellular fluid volume, including plasma and interstitial compartments, leading to hypovolemia and electrolyte imbalance. Correct answer: Extracellular fluid.
11) D2O method helps in calculating which compartment?
a) Plasma volume
b) Extracellular fluid
c) Total body water
d) Interstitial fluid
Explanation: D2O distributes across all fluid compartments (plasma, interstitial, intracellular). Therefore, it is used to measure total body water. Correct answer: Total body water.
Chapter: Excitable Tissues
Topic: Muscle Physiology
Subtopic: Calcium Channels in Skeletal Muscle
Keyword Definitions:
• Calcium channels: Protein channels that allow Ca²⁺ ions to enter cells, vital for muscle contraction and neurotransmission.
• L-type channels: Long-lasting, high-voltage activated channels predominant in skeletal and cardiac muscles.
• T-type channels: Transient, low-voltage activated channels, important in pacemaker activity.
• N-type channels: Found mainly in neurons, involved in neurotransmitter release.
• R-type channels: Resistant calcium channels, less common physiologically.
Lead Question - 2013
Most common type of calcium channels of skeletal muscles are ?
a) T type
b) L type
c) R type
d) N type
Explanation: Skeletal muscle contraction is mediated by L-type calcium channels located in the transverse tubules. These channels act as voltage sensors and couple with ryanodine receptors on the sarcoplasmic reticulum for Ca²⁺ release. Correct answer: L type.
1) Calcium release from sarcoplasmic reticulum in skeletal muscle is triggered by?
a) L-type calcium channel activation
b) T-type calcium channel activation
c) Sodium channel inactivation
d) Potassium efflux
Explanation: Skeletal muscle contraction depends on L-type calcium channel activation in T-tubules, which mechanically couples with ryanodine receptors, leading to sarcoplasmic reticulum calcium release. Correct answer: L-type calcium channel activation.
2) A patient with mutation in ryanodine receptor shows?
a) Malignant hyperthermia
b) Hypokalemia
c) Myasthenia gravis
d) Hyponatremia
Explanation: Mutations in ryanodine receptors cause uncontrolled calcium release during anesthesia, leading to malignant hyperthermia with rigidity, tachycardia, and hyperthermia. Correct answer: Malignant hyperthermia.
3) In cardiac muscle, the main calcium channel responsible for excitation-contraction coupling is?
a) L-type
b) T-type
c) N-type
d) P-type
Explanation: Cardiac contraction relies on L-type calcium channels, which mediate calcium influx during plateau phase, triggering further calcium-induced calcium release from sarcoplasmic reticulum. Correct answer: L-type.
4) A patient treated with nifedipine. Which calcium channel is blocked?
a) L-type
b) T-type
c) N-type
d) R-type
Explanation: Nifedipine, a dihydropyridine calcium channel blocker, selectively inhibits L-type calcium channels, reducing vascular smooth muscle contraction and lowering blood pressure. Correct answer: L-type.
5) Which calcium channels are important in pacemaker activity of SA node?
a) L-type
b) T-type
c) N-type
d) R-type
Explanation: T-type calcium channels open transiently at low voltage, contributing to the depolarization phase of SA node pacemaker cells. Correct answer: T-type.
6) A child with congenital myopathy shows impaired excitation-contraction coupling. Likely channel defect?
a) L-type calcium channel
b) Sodium channel
c) Potassium channel
d) Chloride channel
Explanation: Excitation-contraction coupling in skeletal muscle depends on L-type calcium channels functioning as voltage sensors. A defect impairs calcium release from SR, leading to muscle weakness. Correct answer: L-type calcium channel.
7) N-type calcium channels are primarily located in?
a) Skeletal muscle
b) Cardiac muscle
c) Neurons
d) Liver cells
Explanation: N-type calcium channels are located in presynaptic terminals of neurons, playing a role in neurotransmitter release. Correct answer: Neurons.
8) In smooth muscle, calcium entry for contraction mainly occurs through?
a) L-type channels
b) N-type channels
c) R-type channels
d) Sodium leak channels
Explanation: Smooth muscle contraction largely depends on calcium influx through L-type calcium channels, which activate calmodulin and MLCK for actin-myosin interaction. Correct answer: L-type.
9) A patient develops synaptic transmission defect with reduced neurotransmitter release. Likely channel defect?
a) N-type calcium channel
b) L-type calcium channel
c) T-type calcium channel
d) R-type calcium channel
Explanation: N-type calcium channels control neurotransmitter release at presynaptic terminals. Dysfunction reduces exocytosis, impairing synaptic communication. Correct answer: N-type calcium channel.
10) Which calcium channel is responsible for prolonged calcium current in cardiac ventricular myocytes?
a) L-type
b) T-type
c) N-type
d) R-type
Explanation: L-type calcium channels mediate long-lasting inward calcium current during plateau phase of cardiac action potential, crucial for contraction. Correct answer: L-type.
11) Skeletal muscle contraction does not depend on extracellular calcium influx because?
a) Direct mechanical coupling of L-type channel with SR ryanodine receptor
b) Sodium channel influx is sufficient
c) Potassium efflux replaces calcium
d) Myosin does not need calcium
Explanation: In skeletal muscle, excitation-contraction coupling occurs by direct mechanical interaction between L-type channels in T-tubules and ryanodine receptors in SR. Thus, extracellular calcium influx is not essential. Correct answer: Direct mechanical coupling.
Chapter: Cerebral Circulation
Topic: Regulation of Cerebral Blood Flow
Subtopic: Effect of Exercise
Keyword Definitions:
• Cerebral blood flow: Volume of blood passing through 100g of brain tissue per minute, normally about 50 ml/100g/min.
• Autoregulation: Brain maintains constant blood flow despite blood pressure variations.
• Moderate exercise: Physical activity that increases heart rate moderately without excessive oxygen debt.
• Hypercapnia: Increased CO₂ levels, a strong regulator of cerebral blood flow.
• Hypoxia: Low oxygen, also increases cerebral blood flow.
Lead Question - 2013
What is the effect of moderate exercise on cerebral blood flow?
a) Does not change
b) Increases
c) Decreases
d) Initially decreases then increases
Explanation: During moderate exercise, cerebral blood flow remains unchanged due to autoregulation. Increased blood pressure and cardiac output are balanced by cerebral vasoconstriction, keeping flow constant. Correct answer: Does not change.
1) Which factor has the most potent effect on cerebral blood flow?
a) Oxygen
b) Carbon dioxide
c) Hydrogen ions
d) Nitric oxide
Explanation: Cerebral blood flow is most strongly influenced by arterial carbon dioxide concentration. Even slight increases in PaCO₂ cause marked vasodilation. Correct answer: Carbon dioxide.
2) A patient with head injury develops hypoventilation. What happens to cerebral blood flow?
a) Decreases
b) Increases
c) No change
d) Biphasic response
Explanation: Hypoventilation leads to hypercapnia, which dilates cerebral vessels and increases cerebral blood flow, raising intracranial pressure. Correct answer: Increases.
3) Normal cerebral blood flow is approximately?
a) 25 ml/100g/min
b) 35 ml/100g/min
c) 50 ml/100g/min
d) 75 ml/100g/min
Explanation: Normal cerebral blood flow is about 50 ml/100g/min in adults. This ensures adequate oxygen and glucose supply to neurons. Correct answer: 50 ml/100g/min.
4) During severe hypoxia, cerebral blood flow?
a) Increases
b) Decreases
c) Remains constant
d) Initially decreases then stabilizes
Explanation: Hypoxia stimulates cerebral vasodilation to maintain oxygen supply, leading to increased cerebral blood flow. Correct answer: Increases.
5) A patient undergoing hyperventilation during neurosurgery will have?
a) Increased cerebral blood flow
b) Decreased cerebral blood flow
c) No change
d) Fluctuating response
Explanation: Hyperventilation reduces PaCO₂ (hypocapnia), causing vasoconstriction and decreased cerebral blood flow, useful in lowering intracranial pressure. Correct answer: Decreased cerebral blood flow.
6) Which artery supplies the motor cortex controlling leg movement?
a) Anterior cerebral artery
b) Middle cerebral artery
c) Posterior cerebral artery
d) Basilar artery
Explanation: The anterior cerebral artery supplies the medial aspect of cerebral hemispheres, including the motor cortex area for lower limb control. Correct answer: Anterior cerebral artery.
7) Which brain region is most sensitive to hypoxia?
a) Hippocampus
b) Thalamus
c) Cerebellum
d) Medulla
Explanation: Hippocampal neurons are highly sensitive to hypoxia and ischemia, making them vulnerable to injury in low oxygen states. Correct answer: Hippocampus.
8) A patient with ischemic stroke due to middle cerebral artery occlusion will present with?
a) Hemiplegia sparing face
b) Hemiplegia involving face and arm more
c) Hemiplegia involving leg more
d) Ataxia only
Explanation: Middle cerebral artery occlusion causes contralateral hemiplegia involving face and upper limb more than lower limb. Correct answer: Hemiplegia involving face and arm more.
9) Cerebral perfusion pressure is calculated as?
a) Mean arterial pressure + intracranial pressure
b) Mean arterial pressure - intracranial pressure
c) Systolic blood pressure - intracranial pressure
d) Diastolic blood pressure + intracranial pressure
Explanation: Cerebral perfusion pressure = MAP – ICP. Adequate CPP is vital for brain oxygenation. Correct answer: Mean arterial pressure - intracranial pressure.
10) A patient with subarachnoid hemorrhage develops vasospasm. This leads to?
a) Increased cerebral blood flow
b) Decreased cerebral blood flow
c) Normal cerebral blood flow
d) Fluctuating cerebral blood flow
Explanation: Vasospasm after subarachnoid hemorrhage narrows cerebral arteries, reducing cerebral blood flow and causing ischemia. Correct answer: Decreased cerebral blood flow.
11) Autoregulation of cerebral blood flow is effective between which mean arterial pressures?
a) 30-80 mmHg
b) 50-150 mmHg
c) 70-200 mmHg
d) 90-220 mmHg
Explanation: Cerebral autoregulation maintains constant blood flow between MAP 50–150 mmHg. Outside this range, flow varies directly with pressure. Correct answer: 50-150 mmHg.
Chapter: General Physiology
Topic: Membrane Physiology
Subtopic: Ion Channels and Patch-Clamp Technique
Keyword Definitions:
• Patch-clamp: Technique to measure ionic currents through single ion channels.
• Voltage-gated channels: Ion channels opening/closing in response to membrane potential changes.
• Resting Membrane Potential (RMP): Electrical potential difference across resting cell membranes.
• Facilitated diffusion: Passive transport across membranes via carrier proteins.
• Osmotic pressure: Pressure exerted by solutes across semipermeable membranes.
Lead Question - 2013
'Patch-clamp' is used for ?
a) To record facilitated diffusion
b) To record flow in voltage gated channel
c) To record osmotic pressure around semipermeable membrane
d) To record RMP
Explanation: Patch-clamp is a powerful electrophysiological technique for recording ionic currents in individual ion channels, particularly voltage-gated channels. It helps study gating, conductance, and drug effects. Correct answer: b) To record flow in voltage gated channel. Other options relate to different physiological processes not studied by patch-clamp.
1) Which ion channel is primarily responsible for upstroke of neuronal action potential?
a) K+ channels
b) Na+ channels
c) Ca2+ channels
d) Cl- channels
Explanation: The rapid depolarization in neuronal action potential is mediated by opening of voltage-gated Na+ channels, allowing influx of sodium ions. This phase defines the action potential upstroke. Correct answer: b) Na+ channels. Potassium channels act later in repolarization, while calcium channels play supportive roles.
2) A patient with Lambert-Eaton syndrome has impaired neurotransmission due to antibodies against ?
a) Voltage-gated Na+ channels
b) Voltage-gated K+ channels
c) Voltage-gated Ca2+ channels
d) Ligand-gated Cl- channels
Explanation: Lambert-Eaton myasthenic syndrome involves antibodies against presynaptic voltage-gated Ca2+ channels, reducing acetylcholine release at neuromuscular junction. This causes muscle weakness improving with exercise. Correct answer: c) Voltage-gated Ca2+ channels. It differs from myasthenia gravis which affects postsynaptic receptors.
3) Which technique is used to measure membrane potential directly?
a) Patch-clamp
b) Microelectrode insertion
c) Radioisotope flux
d) Fluorescent dyes
Explanation: Microelectrode insertion technique allows direct measurement of membrane potential by impaling a cell and recording voltage difference across its membrane. Correct answer: b) Microelectrode insertion. Patch-clamp mainly records ionic currents, while dyes and isotopes give indirect estimates.
4) A 55-year-old hypertensive patient develops muscle weakness. Patch-clamp study shows reduced Na+ channel activity. Which phase of action potential will be most affected?
a) Depolarization
b) Repolarization
c) Hyperpolarization
d) Resting potential
Explanation: Voltage-gated sodium channels mediate depolarization of the action potential. Reduced activity impairs this initial phase, slowing or blocking excitation. Correct answer: a) Depolarization. Repolarization is mediated by K+ channels, unaffected by sodium channel dysfunction.
5) In cardiac pacemaker cells, which ion channel is critical for spontaneous depolarization?
a) Na+ fast channels
b) K+ channels
c) Funny (If) channels
d) Cl- channels
Explanation: Pacemaker cells rely on funny channels (If), which conduct slow Na+ influx during diastolic depolarization. This automatic activity initiates heartbeats. Correct answer: c) Funny (If) channels. Fast Na+ channels dominate atrial/ventricular depolarization, not pacemaker activity.
6) A young man presents with periodic paralysis triggered by high carbohydrate meals. Patch-clamp shows K+ channel inactivation. What is the diagnosis?
a) Myasthenia gravis
b) Hypokalemic periodic paralysis
c) Hyperkalemic periodic paralysis
d) Lambert-Eaton syndrome
Explanation: Hypokalemic periodic paralysis involves episodic weakness after carbohydrate load or rest, due to defective voltage-gated calcium or potassium channels. Correct answer: b) Hypokalemic periodic paralysis. Patch-clamp aids in confirming channel dysfunction in such disorders.
7) Which ion channel is blocked by tetrodotoxin (puffer fish toxin)?
a) Na+ channels
b) K+ channels
c) Ca2+ channels
d) Cl- channels
Explanation: Tetrodotoxin selectively blocks voltage-gated sodium channels, preventing depolarization and action potential conduction. This causes paralysis and can be fatal. Correct answer: a) Na+ channels. Potassium and calcium channels are unaffected by tetrodotoxin.
8) A patient with cystic fibrosis has defective ion transport due to mutation in ?
a) Voltage-gated Na+ channel
b) CFTR chloride channel
c) Potassium leak channel
d) Calcium channel
Explanation: Cystic fibrosis is caused by mutations in the CFTR gene encoding a chloride channel important for epithelial fluid transport. This leads to thick mucus secretions. Correct answer: b) CFTR chloride channel. Patch-clamp can study defective chloride channel activity.
9) Which ligand-gated channel is activated at the neuromuscular junction?
a) GABA receptor channel
b) Acetylcholine receptor channel
c) NMDA receptor channel
d) Glycine receptor channel
Explanation: At the neuromuscular junction, acetylcholine binds to nicotinic receptors, opening ligand-gated sodium and potassium channels, causing depolarization. Correct answer: b) Acetylcholine receptor channel. Other receptors are inhibitory or central nervous system-specific.
10) A 70-year-old man with Alzheimer’s disease has reduced cholinergic neurotransmission. Which channel activity is most impaired at synapse?
a) Nicotinic receptor channel
b) Voltage-gated Na+ channel
c) Voltage-gated K+ channel
d) Ca2+ leak channel
Explanation: Alzheimer’s disease involves loss of cholinergic neurons, reducing acetylcholine release and nicotinic receptor activity at synapses. Correct answer: a) Nicotinic receptor channel. This underlies cognitive deficits and explains why cholinesterase inhibitors are used in therapy.
Chapter: General Physiology
Topic: Cell Communication
Subtopic: Gap Junctions and Intercellular Signaling
Keyword Definitions:
• Gap junctions: Specialized intercellular connections allowing ions and molecules to pass directly between cells.
• Connexins: Protein subunits forming channels in gap junctions.
• Cardiac myocytes: Muscle cells of the heart responsible for contraction.
• Smooth muscle: Involuntary, non-striated muscle found in visceral organs.
• Impulse transmission: Movement of action potentials between cells for coordinated function.
Lead Question - 2013
Gap junctions?
a) Are absent in cardiac muscles
b) Are absent in smooth muscles
c) Are present in cardiac muscles to transmit impulse from one to another myocyte
d) Are present in cardiac muscles but no role
Explanation: Gap junctions, made of connexins, are crucial for electrical coupling in cardiac myocytes. They allow action potentials to spread rapidly, ensuring coordinated contraction. Correct answer: c) Are present in cardiac muscles to transmit impulse from one to another myocyte. They are also found in smooth muscle for synchronous contraction.
1) Which protein forms the structural unit of gap junctions?
a) Integrin
b) Connexin
c) Cadherin
d) Selectin
Explanation: Gap junctions are composed of connexin proteins. Six connexins form a connexon, and two connexons align to create a functional gap junction channel. Correct answer: b) Connexin. Cadherins and integrins are adhesion proteins, not channel-forming proteins.
2) A patient with atrial fibrillation shows impaired intercellular electrical coupling. Which structure is most likely defective?
a) Desmosomes
b) Tight junctions
c) Gap junctions
d) Hemidesmosomes
Explanation: Atrial fibrillation often involves dysfunction in gap junctions, which mediate cell-to-cell conduction of impulses. Their alteration leads to arrhythmias. Correct answer: c) Gap junctions. Tight junctions regulate paracellular permeability but not impulse spread.
3) Gap junctions allow passage of which molecules?
a) Proteins
b) DNA
c) Ions and small molecules
d) Large lipids
Explanation: Gap junctions permit ions and small molecules (less than 1 kDa) like calcium, ATP, and second messengers to pass between cells. Correct answer: c) Ions and small molecules. Large macromolecules like proteins and DNA cannot pass.
4) A neonate presents with arrhythmias and skin abnormalities due to connexin mutation. This syndrome reflects dysfunction in?
a) Gap junctions
b) Desmosomes
c) Adherens junctions
d) Hemidesmosomes
Explanation: Mutations in connexins impair gap junctions, leading to defective impulse conduction in the heart and abnormal keratinocyte communication in skin. Correct answer: a) Gap junctions. Other junctions primarily mediate adhesion, not ion flow.
5) Which of the following is NOT a function of gap junctions?
a) Electrical coupling
b) Synchronous contraction
c) Paracellular absorption
d) Metabolic cooperation
Explanation: Gap junctions mediate electrical coupling, synchronous activity, and metabolic cooperation. They do not participate in paracellular absorption, which is regulated by tight junctions. Correct answer: c) Paracellular absorption. Gap junctions are key for coordinated function in heart and smooth muscle.
6) A patient with heart failure has reduced connexin-43 expression. Which physiological process will be most impaired?
a) Cardiac impulse propagation
b) Sodium-potassium pump activity
c) Calcium release from SR
d) Myosin cross-bridge cycling
Explanation: Connexin-43 is a major gap junction protein in ventricular myocardium. Its reduction decreases impulse propagation, causing conduction delays and arrhythmias. Correct answer: a) Cardiac impulse propagation. Pump activity and contractile proteins remain intact.
7) Which junction is most important for maintaining barrier integrity of epithelial cells?
a) Gap junction
b) Tight junction
c) Desmosome
d) Adherens junction
Explanation: Tight junctions seal epithelial cells, preventing leakage of solutes across paracellular spaces. Correct answer: b) Tight junction. Gap junctions communicate signals, not barrier integrity. Desmosomes provide strength, and adherens junctions link actin filaments.
8) A 40-year-old man presents with smooth muscle dysfunction and impaired uterine contractions. Which junction defect could explain this?
a) Gap junction
b) Tight junction
c) Focal adhesion
d) Desmosome
Explanation: Smooth muscle contraction synchronization depends on gap junctions. In uterus, they increase near term to enable labor. Defects impair contractions. Correct answer: a) Gap junction. Tight junctions regulate barriers, not muscle function.
9) Which dye transfer experiment demonstrates functional gap junction communication?
a) Lucifer yellow
b) Hematoxylin
c) Eosin
d) Safranin
Explanation: Lucifer yellow is a small fluorescent dye that diffuses through gap junctions, demonstrating intercellular communication. Correct answer: a) Lucifer yellow. Other dyes stain tissues but do not assess junctional transfer.
10) A patient with ventricular arrhythmia has gap junctional uncoupling due to ischemia. Which mechanism explains this finding?
a) Acidosis closes gap junctions
b) Calcium influx strengthens gap junctions
c) Hypoxia opens more connexons
d) ATP depletion activates channels
Explanation: During ischemia, acidosis and calcium overload close gap junctions, impairing conduction and predisposing to arrhythmias. Correct answer: a) Acidosis closes gap junctions. Hypoxia and ATP depletion worsen function but do not directly open channels.