Topic: Endocrine Physiology
Subtopic: Hormone Receptors and Signal Transduction
Keyword Definitions:
• JAK-STAT pathway: A signaling cascade used by cytokines and some hormones for gene transcription.
• Growth Hormone (GH): Anterior pituitary hormone that stimulates growth, metabolism, and IGF-1 release.
• TSH: Thyroid-stimulating hormone acting via cAMP pathway.
• Thyroxine: Thyroid hormone acting via nuclear receptors.
• FSH: Follicle-stimulating hormone acting via G-protein coupled cAMP signaling.
Lead Question - 2013
Which hormone acts on JAK-STAT kinase receptor?
a) TSH
b) Thyroxine
c) GH
d) FSH
Explanation:
Growth hormone binds to its receptor, activating the JAK-STAT pathway, leading to transcription of IGF-1 and growth-related genes. Other hormones listed use G-protein or nuclear receptors. Answer: c) GH.
1) Prolactin receptor signaling is mediated by:
a) JAK-STAT pathway
b) cAMP pathway
c) Tyrosine kinase pathway
d) IP3-DAG pathway
Explanation:
Prolactin binds its receptor and activates JAK-STAT signaling, which stimulates transcription of milk protein genes in mammary glands. Answer: a) JAK-STAT pathway.
2) Clinical: A child with GH receptor mutation will show:
a) Gigantism
b) Laron dwarfism
c) Acromegaly
d) Hypothyroidism
Explanation:
GH receptor mutation blocks JAK-STAT signaling, leading to Laron dwarfism with short stature despite normal GH but low IGF-1. Answer: b) Laron dwarfism.
3) Which cytokines also act via JAK-STAT pathway?
a) Interleukins
b) Insulin
c) Catecholamines
d) Steroids
Explanation:
Many interleukins, interferons, and hematopoietic growth factors activate the JAK-STAT pathway to modulate immune responses. Answer: a) Interleukins.
4) Clinical: A patient with excess GH post-epiphyseal closure develops:
a) Gigantism
b) Acromegaly
c) Dwarfism
d) Osteoporosis
Explanation:
Excess GH in adults causes acromegaly due to JAK-STAT mediated bone and soft tissue overgrowth. Answer: b) Acromegaly.
5) GH primarily increases growth via which mediator?
a) Thyroxine
b) Cortisol
c) IGF-1
d) Insulin
Explanation:
GH induces hepatic production of IGF-1 via JAK-STAT pathway, which mediates bone and muscle growth. Answer: c) IGF-1.
6) Clinical: In chronic kidney disease, growth retardation may occur due to impaired:
a) GH secretion
b) IGF-1 production
c) Cortisol secretion
d) Thyroid secretion
Explanation:
CKD patients may have normal GH but impaired hepatic IGF-1 production, reducing JAK-STAT mediated growth. Answer: b) IGF-1 production.
7) Which of the following hormones acts through nuclear receptors, unlike GH?
a) Cortisol
b) Prolactin
c) Erythropoietin
d) GH
Explanation:
Cortisol is a steroid hormone acting via intracellular nuclear receptors, while GH, prolactin, and erythropoietin act via JAK-STAT. Answer: a) Cortisol.
8) Erythropoietin receptor signaling uses:
a) JAK-STAT pathway
b) cAMP pathway
c) MAP kinase pathway
d) Nuclear receptor pathway
Explanation:
Erythropoietin receptor belongs to cytokine receptor family, activating JAK-STAT signaling to stimulate RBC production. Answer: a) JAK-STAT pathway.
9) Clinical: A patient with chronic inflammation has anemia due to high IL-6 levels. Which pathway mediates IL-6 effects?
a) JAK-STAT pathway
b) cAMP pathway
c) IP3-DAG pathway
d) MAP kinase pathway
Explanation:
IL-6 acts via JAK-STAT pathway, stimulating hepcidin production, reducing iron absorption and causing anemia of chronic disease. Answer: a) JAK-STAT pathway.
10) GH receptor belongs to which receptor family?
a) G-protein coupled receptor
b) Tyrosine kinase receptor
c) Cytokine receptor family
d) Nuclear receptor family
Explanation:
GH receptor belongs to cytokine receptor superfamily, using JAK-STAT signaling rather than intrinsic kinase activity. Answer: c) Cytokine receptor family.
Topic: Endocrine Physiology
Subtopic: Mechanism of Hormone Action
Keyword Definitions:
• Thyroid hormone: Hormones T3 and T4 secreted by thyroid gland regulating growth and metabolism.
• Nuclear receptor: Intracellular receptor binding hormone to regulate gene transcription.
• TSH receptor: Membrane-bound G-protein receptor that regulates thyroid hormone secretion.
• Cytoplasmic receptor: Found in steroid hormone pathways before translocation to nucleus.
• Transcription factor: Protein that binds DNA to control gene expression.
Lead Question - 2013
Thyroid hormone binds to which receptor?
a) Membrane
b) Cytoplasmic
c) Nuclear
d) None
Explanation:
Thyroid hormones (mainly T3) enter cells and bind nuclear receptors, influencing transcription of genes controlling growth, basal metabolic rate, and development. Unlike peptide hormones, they do not act on cell surface receptors. Answer: c) Nuclear.
1) Which thyroid hormone has greater receptor affinity?
a) T4
b) T3
c) Reverse T3
d) Both equal
Explanation:
T3 has higher affinity for nuclear receptors and is the biologically active form, whereas T4 is converted into T3 in tissues. Answer: b) T3.
2) Clinical: A patient with defective deiodinase enzyme shows low T3 despite normal T4. Which consequence is expected?
a) Normal metabolism
b) Hypothyroid features
c) Hyperthyroid features
d) No effect
Explanation:
Conversion of T4 to T3 is impaired, leading to decreased nuclear receptor activation and features of hypothyroidism despite normal T4. Answer: b) Hypothyroid features.
3) Thyroid hormone receptors are usually bound to:
a) Heat shock proteins
b) DNA response elements
c) Ribosomes
d) mRNA
Explanation:
Thyroid receptors reside in the nucleus, bound to DNA at thyroid response elements, modulating transcription when T3 binds. Answer: b) DNA response elements.
4) Clinical: A child with congenital hypothyroidism untreated will show:
a) Gigantism
b) Cretinism
c) Acromegaly
d) Addison’s disease
Explanation:
Thyroid hormones regulate brain growth and development in infants. Deficiency leads to severe mental retardation and stunted growth termed cretinism. Answer: b) Cretinism.
5) Which receptor family does thyroid hormone receptor belong to?
a) G-protein coupled receptor
b) Tyrosine kinase receptor
c) Nuclear receptor family
d) Cytokine receptor family
Explanation:
Thyroid hormone receptor belongs to nuclear receptor superfamily, acting as transcription factors upon ligand binding. Answer: c) Nuclear receptor family.
6) Clinical: A patient with hyperthyroidism shows weight loss despite good appetite. Which mechanism explains this?
a) Increased transcription via nuclear receptors
b) Blocked insulin action
c) Poor absorption
d) Reduced protein synthesis
Explanation:
Hyperthyroidism enhances metabolic rate by increased nuclear receptor-mediated gene transcription, leading to weight loss despite increased appetite. Answer: a) Increased transcription via nuclear receptors.
7) Reverse T3 is:
a) Active hormone
b) Inactive metabolite
c) Potent receptor binder
d) Same as T3
Explanation:
Reverse T3 is an inactive metabolite of T4 that cannot bind nuclear receptors effectively, serving as a regulatory mechanism. Answer: b) Inactive metabolite.
8) Which organ converts most T4 into T3?
a) Liver
b) Kidney
c) Brain
d) Stomach
Explanation:
Peripheral conversion of T4 to active T3 mainly occurs in the liver, followed by kidneys and other tissues, ensuring metabolic regulation. Answer: a) Liver.
9) Clinical: In euthyroid sick syndrome, T4 levels are normal but T3 is low. Which receptor activity is affected?
a) Cytoplasmic
b) Nuclear
c) Membrane
d) G-protein
Explanation:
Low T3 in euthyroid sick syndrome reduces nuclear receptor activation, mimicking hypothyroidism despite normal TSH and T4 levels. Answer: b) Nuclear.
10) Which thyroid hormone form binds more avidly to nuclear receptor?
a) T4
b) T3
c) rT3
d) Both equally
Explanation:
T3 binds nuclear receptors with higher affinity and greater transcriptional effect compared to T4 or rT3. Answer: b) T3.
Topic: Renal Physiology
Subtopic: Body Fluid Compartments and Osmolality
Keyword Definitions:
• Serum osmolality: Measure of solute concentration in plasma, expressed as mOsm/kg of water.
• Sodium: Main extracellular ion contributing to serum osmolality.
• ADH (Vasopressin): Hormone regulating water reabsorption to maintain osmolality.
• Hyponatremia: Decreased sodium concentration causing low serum osmolality.
• Hypernatremia: Increased sodium concentration causing elevated serum osmolality.
Lead Question - 2013
Normal range of serum osmolality is (mOsm/Kg)?
a) 280 - 300
b) 250 - 270
c) 300 - 320
d) 210 - 230
Explanation:
Serum osmolality normally ranges between 280–300 mOsm/kg, primarily maintained by sodium and water balance. Deviation from this range indicates fluid-electrolyte imbalance, as seen in hyponatremia or hypernatremia. Regulation involves thirst and ADH secretion. Answer: a) 280 - 300.
1) Main determinant of serum osmolality?
a) Glucose
b) Sodium
c) Urea
d) Potassium
Explanation:
Sodium is the major extracellular cation, accounting for most of serum osmolality. Glucose and urea contribute minimally under normal conditions. Answer: b) Sodium.
2) Clinical: A patient with sodium 120 mEq/L is likely to have serum osmolality?
a) Below 280
b) 280-300
c) Above 320
d) Normal
Explanation:
Severe hyponatremia lowers serum osmolality significantly below the normal range, often causing neurological symptoms like confusion or seizures. Answer: a) Below 280.
3) Which hormone plays a central role in regulating serum osmolality?
a) Aldosterone
b) Vasopressin (ADH)
c) Insulin
d) Cortisol
Explanation:
ADH regulates water reabsorption in renal collecting ducts, adjusting plasma osmolality by concentrating or diluting urine as required. Answer: b) Vasopressin (ADH).
4) Clinical: A diabetic patient in hyperglycemia shows serum osmolality 330 mOsm/kg. What is this condition?
a) Hyponatremia
b) Hypo-osmolality
c) Hyperosmolality
d) Normal
Explanation:
Excess glucose acts as an effective osmole, elevating serum osmolality above 300, leading to hyperosmolar states. Answer: c) Hyperosmolality.
5) Osmoreceptors regulating ADH secretion are located in:
a) Medulla oblongata
b) Hypothalamus
c) Pituitary gland
d) Cerebellum
Explanation:
Osmoreceptors in the hypothalamus detect plasma osmolality changes and stimulate posterior pituitary to release ADH, maintaining balance. Answer: b) Hypothalamus.
6) Clinical: A patient with SIADH will have?
a) Increased serum osmolality
b) Decreased serum osmolality
c) Normal osmolality
d) No change
Explanation:
SIADH causes excess ADH release, leading to water retention, dilutional hyponatremia, and decreased serum osmolality. Answer: b) Decreased serum osmolality.
7) Which of the following contributes minimally to effective osmolality?
a) Sodium
b) Glucose
c) Urea
d) Potassium
Explanation:
Urea equilibrates across membranes and contributes little to effective osmolality, unlike sodium and glucose, which influence water movement. Answer: c) Urea.
8) Clinical: In dehydration, serum osmolality will be?
a) Low
b) High
c) Normal
d) Zero
Explanation:
Loss of water without proportional solute loss increases serum osmolality above normal range, stimulating thirst and ADH release. Answer: b) High.
9) Formula to calculate serum osmolality?
a) 2(Na) + Glucose/18 + BUN/2.8
b) Na + K + Cl
c) 2(K) + Creatinine
d) Na + Glucose + Protein
Explanation:
Serum osmolality is calculated as: 2 × [Na] + [Glucose]/18 + [BUN]/2.8. This approximates measured osmolality. Answer: a) 2(Na) + Glucose/18 + BUN/2.8.
10) Clinical: In mannitol therapy for cerebral edema, serum osmolality is?
a) Increased
b) Decreased
c) Normal
d) Unchanged
Explanation:
Mannitol is an osmotic agent that increases serum osmolality, drawing water out of brain cells to reduce intracranial pressure. Answer: a) Increased.
Topic: Pineal Gland Hormones
Subtopic: Melatonin Functions
Keyword Definitions:
Melatonin: Hormone secreted by pineal gland that regulates circadian rhythm.
Circadian rhythm: 24-hour cycle regulating sleep and wakefulness.
ACTH: Adrenocorticotropic hormone that stimulates cortisol secretion.
TSH: Thyroid-stimulating hormone regulating thyroid function.
Sleep induction: Physiological process of initiating sleep.
Lead Question (2013):
The following is the action of melatonin?
a) Facilitates ACTH secretion
b) Prevents sleep induction
c) Regulates the circadian day night rhythm
d) Release of TSH
Explanation: Melatonin, secreted by the pineal gland, regulates the circadian rhythm and promotes sleep induction. It does not stimulate ACTH or TSH release. Instead, its primary role is maintaining the body’s biological clock, especially the day-night cycle. Answer: c) Regulates the circadian day night rhythm.
1) Guess Question:
Which receptor type mediates melatonin action in the brain?
a) MT1 and MT2 receptors
b) Adrenergic receptors
c) Dopaminergic receptors
d) Serotonin receptors
Explanation: Melatonin exerts its biological actions primarily through MT1 and MT2 receptors located in the suprachiasmatic nucleus of the hypothalamus. These receptors regulate sleep-wake cycles and circadian rhythms, while adrenergic, dopaminergic, and serotonin receptors mediate other pathways. Answer: a) MT1 and MT2 receptors.
2) Guess Question:
A 22-year-old student complains of jet lag after traveling abroad. Which hormone supplementation helps?
a) Cortisol
b) Insulin
c) Melatonin
d) Aldosterone
Explanation: Jet lag occurs due to disruption of circadian rhythm. Supplementation with melatonin can help reset the biological clock, improving sleep quality. Cortisol, insulin, and aldosterone have no role in regulating circadian rhythm adaptation during jet lag. Answer: c) Melatonin.
3) Guess Question:
Melatonin secretion is maximum during:
a) Daytime
b) Evening
c) Midnight
d) Early morning
Explanation: Melatonin secretion peaks during midnight, coinciding with the dark phase of the light-dark cycle. Its release is suppressed by light exposure and enhanced in darkness. This secretion pattern synchronizes sleep-wake cycles. Answer: c) Midnight.
4) Guess Question:
Which nucleus in the hypothalamus is primarily influenced by melatonin?
a) Suprachiasmatic nucleus
b) Arcuate nucleus
c) Ventromedial nucleus
d) Mammillary nucleus
Explanation: The suprachiasmatic nucleus of the hypothalamus acts as the master circadian clock, receiving melatonin signals to regulate biological rhythms. Other hypothalamic nuclei regulate hunger, satiety, or memory functions. Answer: a) Suprachiasmatic nucleus.
5) Guess Question:
A patient with seasonal affective disorder (SAD) is most likely treated with:
a) Bright light therapy
b) Insulin
c) Aldosterone
d) Estrogen therapy
Explanation: Seasonal affective disorder is associated with altered melatonin secretion due to shorter daylight in winter. Bright light therapy helps reset circadian rhythm and improve mood. Insulin, aldosterone, or estrogen are unrelated. Answer: a) Bright light therapy.
6) Guess Question:
Inhibition of melatonin secretion occurs due to:
a) Darkness
b) Bright light exposure
c) Sleep deprivation
d) Starvation
Explanation: Exposure to bright light inhibits melatonin secretion by stimulating retinal input to the suprachiasmatic nucleus. Darkness enhances melatonin release, promoting sleep. Sleep deprivation and starvation affect metabolism, not direct melatonin inhibition. Answer: b) Bright light exposure.
7) Guess Question:
A 60-year-old man with insomnia is prescribed melatonin. Its therapeutic action is:
a) Increasing cortisol
b) Inducing sleep
c) Enhancing thyroid function
d) Increasing aldosterone
Explanation: Exogenous melatonin is used in insomnia to induce sleep and restore circadian rhythm. It does not affect cortisol, thyroid, or aldosterone secretion. Answer: b) Inducing sleep.
8) Guess Question:
Melatonin is synthesized from which precursor?
a) Dopamine
b) Serotonin
c) Histamine
d) Acetylcholine
Explanation: Melatonin is synthesized from serotonin through enzymatic conversion involving N-acetyltransferase and hydroxyindole-O-methyltransferase. Dopamine, histamine, and acetylcholine are unrelated neurotransmitters. Answer: b) Serotonin.
9) Guess Question:
A child with a pineal gland tumor may present with:
a) Precocious puberty
b) Delayed puberty
c) Gigantism
d) Diabetes insipidus
Explanation: Pineal gland tumors often reduce melatonin secretion, removing inhibitory influence on gonadotropin release, leading to precocious puberty. Gigantism, delayed puberty, or diabetes insipidus are due to other endocrine dysfunctions. Answer: a) Precocious puberty.
10) Guess Question:
Melatonin is metabolized mainly in the:
a) Kidney
b) Liver
c) Pancreas
d) Adrenal gland
Explanation: Melatonin is metabolized in the liver by cytochrome P450 enzymes, producing 6-hydroxymelatonin sulfate excreted in urine. Kidneys excrete metabolites, while pancreas and adrenal glands are not involved in metabolism. Answer: b) Liver.
Topic: Transport Mechanisms in Kidney
Subtopic: Na+-K+-Cl- Cotransporter
Keyword Definitions:
Na+-K+-Cl- cotransporter: Membrane protein that reabsorbs sodium, potassium, and chloride ions in renal tubules.
Transmembrane domain: Hydrophobic region of protein that spans lipid bilayer.
Loop of Henle: Nephron segment important for countercurrent mechanism.
Thiazide diuretics: Drugs acting on sodium-chloride cotransporter.
Loop diuretics: Drugs inhibiting Na+-K+-Cl- cotransporter in thick ascending limb.
Lead Question (2013):
Na+-K+-Cl- cotransporter contains?
a) 5 transmembrane spanning domain
b) 7 transmembrane spanning domain
c) 9 transmembrane spanning domain
d) 12 transmembrane spanning domain
Explanation: The Na+-K+-Cl- cotransporter is an integral membrane protein with 12 transmembrane spanning domains. It plays a crucial role in salt reabsorption, particularly in the thick ascending limb of the loop of Henle. Loop diuretics inhibit this transporter. Answer: d) 12 transmembrane spanning domain.
1) Guess Question:
Which nephron segment expresses the Na+-K+-Cl- cotransporter predominantly?
a) Proximal tubule
b) Thick ascending limb of loop of Henle
c) Distal tubule
d) Collecting duct
Explanation: The Na+-K+-Cl- cotransporter is localized mainly in the thick ascending limb of the loop of Henle. This segment reabsorbs significant sodium, potassium, and chloride ions, crucial for urine concentration. Answer: b) Thick ascending limb of loop of Henle.
2) Guess Question:
A patient with edema is prescribed furosemide. Its target site is:
a) Na+-Cl- cotransporter
b) Na+-K+-Cl- cotransporter
c) Na+-glucose cotransporter
d) Na+-H+ exchanger
Explanation: Furosemide, a loop diuretic, specifically inhibits the Na+-K+-Cl- cotransporter in the thick ascending limb of the loop of Henle, enhancing diuresis. Other transporters are not affected. Answer: b) Na+-K+-Cl- cotransporter.
3) Guess Question:
Which ion movement drives the Na+-K+-Cl- cotransporter?
a) Passive chloride gradient
b) Sodium electrochemical gradient
c) Active potassium pumping
d) Water reabsorption
Explanation: The Na+-K+-Cl- cotransporter relies on the sodium electrochemical gradient, maintained by Na+/K+ ATPase, to drive cotransport of potassium and chloride. Passive chloride movement and water reabsorption are secondary. Answer: b) Sodium electrochemical gradient.
4) Guess Question:
A 50-year-old hypertensive patient on loop diuretics develops hypokalemia. The mechanism is:
a) Enhanced distal sodium delivery leading to potassium loss
b) Direct potassium secretion in proximal tubule
c) Decreased renin release
d) Reduced aldosterone sensitivity
Explanation: Loop diuretics inhibit Na+-K+-Cl- cotransporter, increasing sodium delivery to distal nephron, enhancing potassium secretion, leading to hypokalemia. Direct proximal secretion and reduced renin/aldosterone sensitivity are not primary mechanisms. Answer: a) Enhanced distal sodium delivery leading to potassium loss.
5) Guess Question:
Which diuretic acts on Na+-Cl- cotransporter in the distal tubule?
a) Thiazides
b) Loop diuretics
c) Carbonic anhydrase inhibitors
d) Potassium-sparing diuretics
Explanation: Thiazide diuretics inhibit the Na+-Cl- cotransporter in the distal convoluted tubule, enhancing sodium and water excretion. Loop diuretics inhibit Na+-K+-Cl-, while carbonic anhydrase inhibitors and potassium-sparing diuretics act elsewhere. Answer: a) Thiazides.
6) Guess Question:
A child presents with polyuria, polydipsia, and hypokalemia. Genetic mutation in which transporter is likely?
a) Na+-Cl- cotransporter
b) Na+-K+-Cl- cotransporter
c) Aquaporin-2 channels
d) Na+-glucose cotransporter
Explanation: Mutations in the Na+-K+-Cl- cotransporter cause Bartter syndrome, leading to polyuria, polydipsia, and hypokalemia due to defective reabsorption in the thick ascending limb. Answer: b) Na+-K+-Cl- cotransporter.
7) Guess Question:
Inhibition of Na+-K+-Cl- cotransporter results in:
a) Dilution of urine
b) Concentrated urine
c) Reduced sodium excretion
d) Increased blood pressure
Explanation: Inhibition of Na+-K+-Cl- cotransporter prevents solute reabsorption in the thick ascending limb, impairing countercurrent multiplication, resulting in dilute urine and natriuresis. Answer: a) Dilution of urine.
8) Guess Question:
A 40-year-old man develops hearing loss while on high-dose loop diuretics. The cause is:
a) Ototoxicity from Na+-K+-Cl- cotransporter inhibition
b) Middle ear infection
c) Damage to auditory ossicles
d) Hypothyroidism
Explanation: Loop diuretics can cause ototoxicity by inhibiting Na+-K+-Cl- cotransporters in the stria vascularis of the inner ear, leading to sensorineural hearing loss. Answer: a) Ototoxicity from Na+-K+-Cl- cotransporter inhibition.
9) Guess Question:
Which electrolyte imbalance is commonly associated with loop diuretic therapy?
a) Hyperkalemia
b) Hypokalemia
c) Hypernatremia
d) Hypercalcemia
Explanation: Loop diuretics cause increased sodium delivery to distal nephron, leading to increased potassium excretion, resulting in hypokalemia. They also promote calcium loss, not hypercalcemia. Answer: b) Hypokalemia.
10) Guess Question:
Na+-K+-Cl- cotransporter is encoded by which gene family?
a) SLC12A family
b) SLC5A family
c) SLC9A family
d) SLC22A family
Explanation: The Na+-K+-Cl- cotransporter belongs to the solute carrier family 12 (SLC12A), which encodes cation-chloride cotransporters. SLC5A encodes sodium-glucose, SLC9A encodes sodium-hydrogen exchangers, and SLC22A encodes organic ion transporters. Answer: a) SLC12A family.
Chapter: Hematology
Topic: Hemostasis
Subtopic: Von Willebrand Factor
Keyword Definitions:
Von Willebrand factor (vWF): Glycoprotein important for platelet adhesion and factor VIII stabilization.
Endothelial cells: Cells lining blood vessels that synthesize and release vWF.
Megakaryocytes: Large bone marrow cells that give rise to platelets and store vWF.
Hepatocytes: Liver cells primarily involved in clotting factor synthesis but not vWF.
Hemostasis: Process preventing blood loss involving vasoconstriction, platelets, and clotting factors.
Lead Question (2013):
Von Willebrand factor is synthesized by all except?
a) Endothelial cells
b) Megakaryocytes
c) Hepatocytes
d) None
Explanation: Von Willebrand factor is synthesized by endothelial cells and stored in Weibel-Palade bodies, and also by megakaryocytes stored in platelet α-granules. Hepatocytes do not produce vWF, though they synthesize other clotting factors. Answer: c) Hepatocytes.
1) Guess Question:
Von Willebrand factor primarily mediates:
a) Platelet adhesion
b) Fibrin degradation
c) Prothrombin activation
d) Plasminogen activation
Explanation: vWF is critical for platelet adhesion to subendothelial collagen at injury sites. It also carries and stabilizes factor VIII, but it does not directly activate prothrombin or plasminogen. Answer: a) Platelet adhesion.
2) Guess Question:
A patient with recurrent nosebleeds has prolonged bleeding time but normal platelet count. The likely cause is:
a) Hemophilia A
b) Von Willebrand disease
c) Thrombocytopenia
d) Vitamin K deficiency
Explanation: Von Willebrand disease causes defective platelet adhesion and prolongs bleeding time, with normal platelet count. Hemophilia A shows factor VIII deficiency, thrombocytopenia lowers platelet count, and vitamin K deficiency affects clotting factor synthesis. Answer: b) Von Willebrand disease.
3) Guess Question:
Von Willebrand factor is stored in endothelial cells within:
a) Lysosomes
b) Weibel-Palade bodies
c) Ribosomes
d) Mitochondria
Explanation: Endothelial cells store vWF in Weibel-Palade bodies, specialized storage organelles. Platelets store vWF in α-granules. Ribosomes and mitochondria are not storage sites for vWF. Answer: b) Weibel-Palade bodies.
4) Guess Question:
A 16-year-old girl presents with menorrhagia and prolonged bleeding after dental extraction. Which lab finding is expected?
a) Increased bleeding time, prolonged aPTT
b) Decreased bleeding time, normal aPTT
c) Increased platelet count, prolonged PT
d) Normal coagulation profile
Explanation: In Von Willebrand disease, bleeding time is prolonged due to defective platelet adhesion, and aPTT may be prolonged due to decreased factor VIII stabilization. Platelet count is normal. Answer: a) Increased bleeding time, prolonged aPTT.
5) Guess Question:
Which factor is stabilized in plasma by vWF?
a) Factor V
b) Factor VII
c) Factor VIII
d) Factor IX
Explanation: vWF binds and stabilizes factor VIII in plasma, protecting it from proteolytic degradation. This allows effective participation in the intrinsic coagulation pathway. Answer: c) Factor VIII.
6) Guess Question:
A 22-year-old male with vWF disease presents with excessive bleeding after surgery. First-line therapy is:
a) Vitamin K
b) Desmopressin (DDAVP)
c) Warfarin
d) Heparin
Explanation: Desmopressin stimulates endothelial cells to release stored vWF, improving hemostasis in mild to moderate vWF disease. Vitamin K, warfarin, and heparin are not useful here. Answer: b) Desmopressin (DDAVP).
7) Guess Question:
Von Willebrand disease is inherited as:
a) Autosomal dominant or recessive
b) X-linked dominant
c) X-linked recessive
d) Mitochondrial
Explanation: Most forms of Von Willebrand disease are inherited as autosomal dominant, though rare recessive forms exist. It is not X-linked like hemophilia A or B, nor mitochondrial. Answer: a) Autosomal dominant or recessive.
8) Guess Question:
A 30-year-old woman with vWF disease is scheduled for delivery. To prevent bleeding, the drug of choice is:
a) Desmopressin
b) Aspirin
c) Heparin
d) Warfarin
Explanation: Desmopressin is effective in releasing vWF from endothelial cells during surgery or delivery, reducing bleeding risk. Aspirin increases bleeding, while warfarin and heparin are anticoagulants. Answer: a) Desmopressin.
9) Guess Question:
Which test is most sensitive for screening vWF disease?
a) Platelet count
b) PT test
c) Ristocetin cofactor activity
d) Thrombin time
Explanation: Ristocetin cofactor activity measures platelet aggregation in presence of ristocetin, highly sensitive for vWF disease. Platelet count is normal, PT and thrombin time are usually not prolonged. Answer: c) Ristocetin cofactor activity.
10) Guess Question:
Von Willebrand disease is associated with defective:
a) Platelet aggregation
b) Platelet adhesion
c) Prothrombin activation
d) Factor XIII stabilization
Explanation: vWF deficiency leads to defective platelet adhesion to subendothelial collagen at vascular injury sites. Platelet aggregation is normal, while prothrombin activation and factor XIII stabilization are unaffected. Answer: b) Platelet adhesion.
Topic: Blood Physiology
Subtopic: Erythropoiesis and Gender Differences
Keyword Definitions:
• RBC count: Number of red blood cells per microliter of blood.
• Erythropoietin: Hormone from kidneys stimulating RBC production.
• Estrogen: Female sex hormone influencing hematopoiesis.
• Menstrual blood loss: Regular shedding of blood during menstruation.
• Stem cells: Bone marrow progenitors giving rise to blood cells.
Lead Question - 2013
Females have low RBC count compared to males due to ?
a) Low erythropoietin
b) Menstural blood loss
c) High estrogen
d) Low stem cells
Explanation: Females have lower RBC count than males mainly due to high estrogen, which suppresses erythropoiesis, and menstrual blood loss further contributing. Testosterone in males stimulates erythropoietin secretion, enhancing RBC production. The correct answer is c) High estrogen, as it plays a primary physiological role in reduced counts.
1) A 25-year-old woman presents with chronic fatigue. Her lab shows Hb 10 g/dl. What is the likely cause?
a) Low erythropoietin
b) Menstrual blood loss
c) High estrogen
d) Low stem cells
Explanation: In young menstruating women, chronic mild anemia commonly arises from menstrual blood loss. Estrogen also reduces erythropoiesis, but menstrual loss is clinically more relevant here. The correct answer is b) Menstrual blood loss, explaining the patient’s low hemoglobin with otherwise normal erythropoietin function.
2) Which hormone increases RBC production significantly in males?
a) Progesterone
b) Estrogen
c) Testosterone
d) Cortisol
Explanation: Testosterone stimulates erythropoietin secretion and directly promotes bone marrow activity. This leads to higher RBC counts in males compared to females. The correct answer is c) Testosterone, explaining the gender difference in hemoglobin and hematocrit values.
3) In chronic renal failure, anemia occurs mainly due to deficiency of?
a) Iron
b) Erythropoietin
c) Vitamin B12
d) Folic acid
Explanation: Chronic renal failure leads to reduced erythropoietin secretion from diseased kidneys, resulting in normocytic normochromic anemia. The correct answer is b) Erythropoietin, which is the most important factor impaired in such patients.
4) A 30-year-old female has low Hb, normal iron studies, normal B12 and folate. Most likely cause is?
a) Low stem cells
b) Menstrual blood loss
c) Low erythropoietin
d) High cortisol
Explanation: With normal nutritional and hormonal markers, menstrual blood loss is the commonest explanation for anemia in reproductive-age women. The correct answer is b) Menstrual blood loss.
5) Which of the following reduces erythropoiesis?
a) Hypoxia
b) Testosterone
c) Estrogen
d) Erythropoietin
Explanation: Estrogen inhibits erythropoiesis, unlike hypoxia, testosterone, and erythropoietin, which stimulate RBC production. Hence, females naturally have lower counts than males. The correct answer is c) Estrogen.
6) A 22-year-old female presents with pallor, Hb 9 g/dl, MCV 72 fl, microcytosis. Most probable cause is?
a) Estrogen suppression
b) Iron deficiency from menstruation
c) Stem cell depletion
d) Low erythropoietin
Explanation: Microcytic anemia with low hemoglobin strongly suggests iron deficiency, commonly due to chronic menstrual blood loss. The correct answer is b) Iron deficiency from menstruation.
7) Which is the normal RBC count in adult females?
a) 3.2–3.6 million/cu mm
b) 3.8–4.5 million/cu mm
c) 4.5–5.5 million/cu mm
d) 5.5–6.0 million/cu mm
Explanation: Normal RBC count in females is about 3.8–4.5 million/cu mm, while in males it is 4.5–5.5 million/cu mm. The correct answer is b) 3.8–4.5 million/cu mm, highlighting the physiological difference.
8) A 55-year-old postmenopausal woman shows improved hemoglobin levels compared to her earlier reports. Which factor explains this?
a) Decreased estrogen effect
b) Increased menstrual loss
c) Decreased testosterone
d) Increased cortisol
Explanation: After menopause, estrogen levels decline, reducing its inhibitory effect on erythropoiesis. This leads to improved hemoglobin and RBC count in postmenopausal women. The correct answer is a) Decreased estrogen effect.
9) Which vitamin is essential for RBC DNA synthesis?
a) Vitamin B6
b) Vitamin B12
c) Vitamin C
d) Vitamin K
Explanation: Vitamin B12 is essential for DNA synthesis during RBC maturation. Its deficiency causes megaloblastic anemia. The correct answer is b) Vitamin B12.
10) A 40-year-old man with chronic alcoholism develops macrocytic anemia. The deficiency is most likely?
a) Vitamin B12
b) Folate
c) Iron
d) Erythropoietin
Explanation: Chronic alcoholics frequently develop folate deficiency due to poor diet and malabsorption, leading to macrocytic anemia. The correct answer is b) Folate.
Topic: Muscle Physiology
Subtopic: Muscle Contraction and ATPase Activity
Keyword Definitions:
• ATPase: Enzyme that hydrolyzes ATP to release energy for cellular processes.
• Actin: Thin filament protein in muscles interacting with myosin for contraction.
• Myosin: Thick filament protein with intrinsic ATPase activity driving cross-bridge cycling.
• Troponin: Regulatory protein controlling actin-myosin interaction during contraction.
• Cross-bridge cycle: Repetitive interaction between actin and myosin powered by ATP hydrolysis.
Lead Question - 2013
ATPase activity is present in
a) Actin
b) Myosin
c) Troponin
d) None
Explanation: Myosin contains intrinsic ATPase activity in its head domain, which hydrolyzes ATP to provide energy for cross-bridge cycling and muscle contraction. Actin and troponin are structural and regulatory proteins without enzymatic activity. Answer: b) Myosin.
1) Guess Question:
Which part of myosin possesses ATPase activity?
a) Tail region
b) Head region
c) Rod region
d) Light chains
Explanation: The myosin head contains ATPase activity, which hydrolyzes ATP to ADP and inorganic phosphate, providing energy for the power stroke during contraction. Tail and rod regions are structural. Answer: b) Head region.
2) Guess Question:
Which ion binds to troponin to initiate contraction?
a) Sodium
b) Potassium
c) Calcium
d) Magnesium
Explanation: Calcium binds to troponin C, causing conformational change that moves tropomyosin off actin binding sites, allowing myosin heads with ATPase activity to interact. Answer: c) Calcium.
3) Guess Question:
Which process directly uses myosin ATPase activity?
a) Glycolysis
b) Cross-bridge cycling
c) Oxidative phosphorylation
d) Sodium-potassium pump
Explanation: Myosin ATPase provides energy for cross-bridge cycling in muscle contraction, allowing repetitive attachment, pivoting, and detachment from actin. Glycolysis and oxidative phosphorylation generate ATP, while Na+/K+ pump is unrelated. Answer: b) Cross-bridge cycling.
4) Guess Question:
A patient has myopathy with defective myosin ATPase. Expected finding is:
a) Weak muscle contraction
b) Hyperactive reflexes
c) Normal contraction
d) Increased tone
Explanation: Defective myosin ATPase prevents ATP hydrolysis, reducing energy for cross-bridge cycling. This leads to weak muscle contraction, hypotonia, and exercise intolerance. Answer: a) Weak muscle contraction.
5) Guess Question:
Which filament slides during muscle contraction?
a) Myosin
b) Actin
c) Troponin
d) Titin
Explanation: Actin filaments slide past stationary myosin filaments during contraction. Myosin heads use ATPase activity to pull actin. Troponin and titin are regulatory and elastic elements. Answer: b) Actin.
6) Guess Question:
Which molecule inhibits actin-myosin interaction in relaxed muscle?
a) Tropomyosin
b) Troponin
c) ATP
d) Myosin light chain
Explanation: Tropomyosin blocks actin binding sites in relaxed muscle. Troponin regulates tropomyosin movement, ATP energizes myosin head, but the inhibitor of cross-bridge formation is tropomyosin. Answer: a) Tropomyosin.
7) Guess Question:
Which compound directly provides energy for myosin ATPase?
a) ADP
b) AMP
c) ATP
d) GTP
Explanation: ATP binds myosin head and is hydrolyzed by ATPase activity to ADP + Pi, providing energy for the power stroke and detachment. ADP alone does not provide energy. Answer: c) ATP.
8) Guess Question:
A 10-year-old has congenital myopathy with low myosin ATPase activity. Likely symptom is:
a) Delayed muscle contraction
b) Rapid fatigue
c) Weakness
d) All of the above
Explanation: Low myosin ATPase impairs ATP hydrolysis, slowing cross-bridge cycling, reducing force generation, and causing weakness, delayed contraction, and rapid fatigue. Answer: d) All of the above.
9) Guess Question:
Which filament does not have ATPase activity?
a) Myosin
b) Actin
c) Both
d) None
Explanation: Only myosin has ATPase activity. Actin is a structural filament without enzymatic function. Therefore, actin cannot hydrolyze ATP. Answer: b) Actin.
10) Guess Question:
During rigor mortis, ATP is depleted. Effect on myosin ATPase activity is:
a) Increased activity
b) Decreased activity
c) No cross-bridge detachment
d) Enhanced contraction
Explanation: Without ATP, myosin heads cannot detach from actin despite ATPase presence. Cross-bridges remain attached, causing rigidity (rigor mortis). ATP hydrolysis is required for detachment and relaxation. Answer: c) No cross-bridge detachment.
Topic: Iron Metabolism
Subtopic: Ferritin and Iron Storage
Keyword Definitions:
• Ferritin: Intracellular protein that stores iron and releases it in a controlled fashion.
• Serum ferritin: Circulating ferritin that reflects body iron stores.
• Iron deficiency: Condition with low ferritin, hemoglobin, and iron stores.
• Iron overload: Condition with elevated ferritin and iron deposition in organs.
• Adult male normal range: Standard reference values for clinical interpretation.
Lead Question - 2013
Normal ferritin level in adult male ?
a) 5-10 ng/ml
b) 100-200 ng/ml
c) 500-700 ng/ml
d) 800-900 ng/ml
Explanation: Normal serum ferritin in adult males ranges from 100–200 ng/ml, reflecting adequate iron stores. Low levels indicate iron deficiency, while very high levels may indicate iron overload or inflammation. Answer: b) 100-200 ng/ml.
1) Guess Question:
Low ferritin is most commonly caused by:
a) Hemolysis
b) Chronic blood loss
c) Vitamin B12 deficiency
d) Renal failure
Explanation: Chronic blood loss is the most common cause of low ferritin, leading to iron deficiency anemia. Hemolysis can cause normal or high ferritin, and vitamin B12 deficiency or renal failure do not directly lower ferritin. Answer: b) Chronic blood loss.
2) Guess Question:
Which lab test best reflects total body iron stores?
a) Serum iron
b) Transferrin saturation
c) Serum ferritin
d) Hemoglobin
Explanation: Serum ferritin is the most reliable marker of body iron stores. Serum iron and transferrin saturation fluctuate with diet and inflammation, and hemoglobin changes are late indicators. Answer: c) Serum ferritin.
3) Guess Question:
A patient with chronic inflammation may have:
a) Low ferritin
b) High ferritin
c) Normal ferritin
d) Undetectable ferritin
Explanation: Ferritin is an acute phase reactant, and its levels rise in chronic inflammation or infection, even if iron stores are low. This can mask iron deficiency. Answer: b) High ferritin.
4) Guess Question:
Iron overload disorders are associated with:
a) Ferritin b) Ferritin 100-200 ng/ml
c) Ferritin >500 ng/ml
d) Ferritin
Explanation: Ferritin levels above 500 ng/ml suggest iron overload, as seen in hereditary hemochromatosis or repeated transfusions. Answer: c) Ferritin >500 ng/ml.
5) Guess Question:
Which organ primarily stores ferritin-bound iron?
a) Brain
b) Liver
c) Kidney
d) Heart
Explanation: The liver is the major organ storing iron as ferritin. The spleen and bone marrow also store iron, while the brain and kidney store minimal amounts. Answer: b) Liver.
6) Guess Question:
A 35-year-old man presents with fatigue. Labs: Hb 11 g/dl, ferritin 8 ng/ml. Diagnosis is:
a) Iron deficiency anemia
b) Thalassemia
c) Vitamin B12 deficiency
d) Aplastic anemia
Explanation: Very low ferritin (8 ng/ml) confirms iron deficiency anemia. Hb is mildly reduced, consistent with early anemia. Other causes like thalassemia or B12 deficiency show normal or high ferritin. Answer: a) Iron deficiency anemia.
7) Guess Question:
Which factor falsely elevates ferritin levels?
a) Hemochromatosis
b) Infection
c) Liver disease
d) All of the above
Explanation: Ferritin is an acute phase reactant; it rises in infection, inflammation, liver disease, and genetic iron overload disorders, potentially misleading iron status assessment. Answer: d) All of the above.
8) Guess Question:
Normal ferritin in adult females is generally:
a) 15-150 ng/ml
b) 100-200 ng/ml
c) 500-700 ng/ml
d) 5-10 ng/ml
Explanation: Adult females typically have lower ferritin than males, around 15–150 ng/ml, due to menstrual blood loss and lower iron stores. Answer: a) 15-150 ng/ml.
9) Guess Question:
A patient with ferritin 600 ng/ml and transferrin saturation 80% likely has:
a) Iron deficiency anemia
b) Iron overload
c) Vitamin B12 deficiency
d) Normal iron stores
Explanation: High ferritin and transferrin saturation indicate iron overload, such as hereditary hemochromatosis or repeated transfusions. Answer: b) Iron overload.
10) Guess Question:
Ferritin is measured primarily by:
a) ELISA
b) Western blot
c) PCR
d) Blood smear
Explanation: Serum ferritin is quantified using ELISA, which detects protein levels accurately. Western blot and PCR are not used for routine ferritin measurement. Answer: a) ELISA.
Topic: Fluid and Electrolyte Balance
Subtopic: Sweat and Daily Water Loss
Keyword Definitions:
• Water loss: Fluid eliminated from the body through sweat, urine, respiration, and feces.
• Sweat: Fluid secreted by sweat glands for thermoregulation.
• Normal activities: Routine daily tasks without heavy physical exertion.
• Thermoregulation: The body's process of maintaining internal temperature.
• Fluid balance: Equilibrium between water intake and water loss.
Lead Question - 2013
Daily water loss in sweat during normal activities ?
a) 50 - 100 ml
b) 200 - 400 ml
c) 500 - 700 ml
d) 1000 - 1200 ml
Explanation: During normal daily activities, sweat contributes to approximately 200–400 ml of water loss in adults, helping maintain thermoregulation. Excessive activity or heat can increase this. Other routes like urine and respiration also contribute. Answer: b) 200 - 400 ml.
1) Guess Question:
Which gland is primarily responsible for sweat secretion?
a) Sebaceous gland
b) Eccrine sweat gland
c) Apocrine sweat gland
d) Salivary gland
Explanation: Eccrine sweat glands are widely distributed and secrete watery sweat for thermoregulation. Apocrine glands contribute minimally in normal daily water loss. Sebaceous and salivary glands are not involved in sweat-mediated water loss. Answer: b) Eccrine sweat gland.
2) Guess Question:
What is the main purpose of sweating?
a) Excrete toxins
b) Thermoregulation
c) Lubrication
d) Immunity
Explanation: Sweating primarily helps maintain body temperature by dissipating heat through evaporation. While minor toxin excretion occurs, the main physiological purpose is thermoregulation. Answer: b) Thermoregulation.
3) Guess Question:
Which electrolyte is most abundant in sweat?
a) Potassium
b) Sodium
c) Calcium
d) Magnesium
Explanation: Sodium is the most abundant electrolyte in sweat, followed by chloride and potassium. This helps in water retention and electrolyte balance. Answer: b) Sodium.
4) Guess Question:
A 30-year-old worker in hot conditions loses 1 liter of sweat per hour. Likely symptom is:
a) Dehydration
b) Hypervolemia
c) Bradycardia
d) Hypernatremia
Explanation: Excessive sweating leads to significant water loss, causing dehydration, decreased plasma volume, and possible hypotension. Electrolytes may also be lost. Answer: a) Dehydration.
5) Guess Question:
Which factor increases daily sweat loss?
a) High ambient temperature
b) Fever
c) Exercise
d) All of the above
Explanation: All these factors increase sweat production to maintain body temperature. Normal daily activity contributes moderately, while fever, heat, and exercise significantly increase water loss. Answer: d) All of the above.
6) Guess Question:
During normal activities, respiratory water loss is approximately:
a) 100-200 ml
b) 400-600 ml
c) 700-900 ml
d) 1000-1200 ml
Explanation: Respiration contributes roughly 400–600 ml of daily water loss in adults at rest. Combined with sweat and urine, this maintains total fluid balance. Answer: b) 400-600 ml.
7) Guess Question:
Which hormone reduces sweat rate by increasing water retention?
a) Aldosterone
b) Cortisol
c) ADH
d) Epinephrine
Explanation: Aldosterone promotes sodium and water reabsorption in kidneys, indirectly conserving fluid and reducing excessive sweat loss. ADH also conserves water but acts mainly on kidneys. Answer: a) Aldosterone.
8) Guess Question:
A patient with hypohidrosis will likely show:
a) Excessive sweating
b) Reduced sweat and heat intolerance
c) Hypernatremia
d) Polyuria
Explanation: Hypohidrosis is reduced sweating, leading to impaired thermoregulation and heat intolerance. Other symptoms may include fatigue and hyperthermia during exertion. Answer: b) Reduced sweat and heat intolerance.
9) Guess Question:
Which nervous system controls sweat secretion?
a) Sympathetic
b) Parasympathetic
c) Somatic
d) Central only
Explanation: Sympathetic nervous system stimulates eccrine sweat glands via cholinergic fibers for thermoregulation. Parasympathetic fibers do not control sweat. Answer: a) Sympathetic.
10) Guess Question:
Daily water loss through feces is approximately:
a) 50-100 ml
b) 200-400 ml
c) 500-700 ml
d) 800-1000 ml
Explanation: Normal fecal water loss is small, about 50–100 ml per day in healthy adults. Most daily water loss occurs via urine, sweat, and respiration. Answer: a) 50-100 ml.