Topic: Autonomic Nervous System
Subtopic: Reflexes and Intracranial Pressure Regulation
Keyword Definitions:
- Cushing Reflex: A physiological nervous system response to increased intracranial pressure leading to hypertension, bradycardia, and irregular respiration.
- Intracranial Pressure (ICP): The pressure exerted by fluids such as cerebrospinal fluid (CSF) inside the skull.
- Bradycardia: A slower than normal heart rate, typically less than 60 beats per minute.
- Tachypnoea: Abnormally rapid breathing.
Lead Question - 2013
Cushing reflex is associated with all except ?
a) Hypotension
b) Increased intracranial pressure
c) Bradycardia
d) Tachyponea
Answer and Explanation:
The correct answer is a) Hypotension. The Cushing reflex is a protective physiological response to increased intracranial pressure characterized by hypertension, bradycardia, and irregular or tachypnoea respiratory patterns. Hypotension is not associated with Cushing reflex. Instead, elevated ICP leads to increased systemic blood pressure to maintain cerebral perfusion.
Guessed Questions for NEET PG:
1. Which of the following is not a feature of Cushing reflex?
a) Hypertension
b) Bradycardia
c) Tachypnoea
d) Hypotension
Explanation: The correct answer is d) Hypotension. Cushing reflex results from increased intracranial pressure and leads to hypertension, bradycardia, and tachypnoea to maintain cerebral perfusion. Hypotension is not part of the reflex response.
2. The Cushing reflex is primarily a response to:
a) Hypoxia
b) Hypercapnia
c) Increased intracranial pressure
d) Dehydration
Explanation: The correct answer is c) Increased intracranial pressure. Cushing reflex activates to maintain cerebral perfusion in the face of elevated intracranial pressure by increasing systemic blood pressure, inducing bradycardia and irregular breathing.
3. Clinical manifestation of the Cushing reflex includes:
a) Tachycardia
b) Hypotension
c) Bradycardia
d) Hyperthermia
Explanation: The correct answer is c) Bradycardia. The Cushing reflex features bradycardia, hypertension, and irregular breathing, as a compensatory mechanism to maintain cerebral perfusion pressure during raised ICP.
4. Which cranial nerve is mainly involved in mediating bradycardia during Cushing reflex?
a) Trigeminal nerve
b) Vagus nerve
c) Hypoglossal nerve
d) Facial nerve
Explanation: The correct answer is b) Vagus nerve. Increased ICP stimulates the vagus nerve leading to bradycardia, as part of the Cushing reflex to balance elevated systemic blood pressure.
5. A patient with severe head injury shows high blood pressure, slow pulse, and irregular respiration. This is indicative of:
a) Cushing reflex
b) Mydriasis
c) Horner's syndrome
d) Meniere's disease
Explanation: The correct answer is a) Cushing reflex. The triad of hypertension, bradycardia, and irregular respiration signifies the body's response to high intracranial pressure to maintain cerebral blood flow.
6. A 40-year-old patient with traumatic brain injury develops bradycardia and hypertension. This reflex helps:
a) Reduce ICP
b) Increase cerebral perfusion
c) Decrease cerebral perfusion
d) Cause vasodilation
Explanation: The correct answer is b) Increase cerebral perfusion. The Cushing reflex increases systemic arterial pressure to counteract elevated intracranial pressure, thereby preserving cerebral perfusion.
7. Tachypnoea in Cushing reflex is due to:
a) Metabolic acidosis
b) Medullary ischemia
c) Hyperventilation
d) Hypoxia
Explanation: The correct answer is b) Medullary ischemia. Increased ICP compresses the medulla, leading to irregular respiratory patterns or tachypnoea as part of the Cushing reflex.
8. In Cushing reflex, systemic hypertension occurs to:
a) Increase cardiac output
b) Reduce heart rate
c) Maintain cerebral perfusion
d) Stimulate sweat glands
Explanation: The correct answer is c) Maintain cerebral perfusion. Systemic hypertension compensates for high ICP, ensuring adequate oxygen and nutrient delivery to the brain despite compression.
9. Which part of the brain senses increased ICP in Cushing reflex?
a) Hypothalamus
b) Medulla oblongata
c) Cerebellum
d) Thalamus
Explanation: The correct answer is b) Medulla oblongata. The medulla senses increased intracranial pressure, triggering autonomic responses like bradycardia and hypertension to maintain cerebral blood flow.
10. Which of the following is not part of Cushing's triad?
a) Hypertension
b) Bradycardia
c) Tachypnoea
d) Hypothermia
Explanation: The correct answer is d) Hypothermia. Cushing's triad includes hypertension, bradycardia, and irregular or tachypnoea respiration. Hypothermia is unrelated to the reflex response.
Topic: Autonomic Nervous System
Subtopic: Sympathetic Nervous System
Keyword Definitions:
- Sympathetic Noradrenergic Fibers: Sympathetic nerve fibers that release norepinephrine to activate target organs, primarily involved in the 'fight or flight' response.
- Blood Vessels: Vessels transporting blood throughout the body, regulated by sympathetic nerves for vasoconstriction and vasodilation.
- Sweat Gland: Glands producing sweat, involved in thermoregulation, uniquely innervated by sympathetic cholinergic fibers.
- Heart: Muscular organ pumping blood, controlled by sympathetic noradrenergic fibers increasing heart rate and contractility.
- Eye: Organ of vision, with sympathetic innervation controlling pupil dilation (mydriasis).
Lead Question - 2013
Which of the following does not have sympathetic noradrenergic fibers?
a) Blood vessels
b) Sweat gland
c) Heart
d) Eye
Answer and Explanation:
The correct answer is b) Sweat gland. Unlike other sympathetic target organs that use noradrenaline, sweat glands are uniquely innervated by sympathetic cholinergic fibers. This allows acetylcholine to mediate sweat secretion during thermoregulation. Blood vessels, heart, and eye receive sympathetic noradrenergic fibers, facilitating vasoconstriction, increased cardiac output, and pupil dilation.
Guessed Questions for NEET PG:
1. Sympathetic innervation of sweat glands uses:
a) Noradrenaline
b) Acetylcholine
c) Dopamine
d) Serotonin
Explanation: The correct answer is b) Acetylcholine. Sweat glands are innervated by sympathetic cholinergic fibers, which release acetylcholine, distinguishing them from most other sympathetic targets that use noradrenaline.
2. Which of the following is a function of sympathetic noradrenergic fibers?
a) Increase salivation
b) Decrease heart rate
c) Vasoconstriction
d) Pupil constriction
Explanation: The correct answer is c) Vasoconstriction. Sympathetic noradrenergic fibers release norepinephrine, causing blood vessels to constrict, thereby increasing blood pressure during stress.
3. Sympathetic noradrenergic fibers in the eye control:
a) Lens accommodation
b) Mydriasis
c) Eyelid closure
d) Tear secretion
Explanation: The correct answer is b) Mydriasis. Sympathetic noradrenergic fibers stimulate radial muscles of the iris to dilate the pupil, aiding vision in low light.
4. Which gland uses cholinergic fibers despite being sympathetic?
a) Adrenal medulla
b) Sweat gland
c) Salivary gland
d) Lacrimal gland
Explanation: The correct answer is b) Sweat gland. Sweat glands are unique as they are innervated by sympathetic cholinergic fibers, releasing acetylcholine for thermoregulation.
5. In sympathetic stimulation, the heart responds by:
a) Decreasing rate
b) Increasing rate and contractility
c) Vasodilation
d) Secreting hormones
Explanation: The correct answer is b) Increasing rate and contractility. Sympathetic noradrenergic fibers release norepinephrine, increasing heart rate and force of contraction during stress.
6. Blood vessel constriction during sympathetic activation occurs via:
a) Cholinergic fibers
b) Adrenergic fibers
c) Dopaminergic fibers
d) Serotonergic fibers
Explanation: The correct answer is b) Adrenergic fibers. Sympathetic noradrenergic fibers release norepinephrine to stimulate vasoconstriction, increasing blood pressure during 'fight or flight' response.
7. Which of the following does not use norepinephrine in its sympathetic innervation?
a) Heart
b) Sweat gland
c) Blood vessels
d) Eye
Explanation: The correct answer is b) Sweat gland. Sweat glands use acetylcholine despite being sympathetic targets, whereas the heart, blood vessels, and eye use norepinephrine.
8. Adrenergic fibers primarily release:
a) Acetylcholine
b) Noradrenaline
c) Dopamine
d) GABA
Explanation: The correct answer is b) Noradrenaline. Adrenergic fibers, part of the sympathetic nervous system, release norepinephrine to stimulate target organs during stress responses.
9. Sympathetic control of pupil dilation involves:
a) Sphincter pupillae muscle
b) Ciliary muscle
c) Radial muscle of iris
d) Orbicularis oculi
Explanation: The correct answer is c) Radial muscle of iris. Sympathetic noradrenergic fibers stimulate the radial muscle, causing pupil dilation (mydriasis) for improved vision in dim light.
10. Sympathetic noradrenergic fibers originate from:
a) Parasympathetic ganglia
b) Sympathetic ganglia
c) Spinal cord gray matter
d) Dorsal root ganglion
Explanation: The correct answer is b) Sympathetic ganglia. Postganglionic sympathetic noradrenergic fibers arise from sympathetic ganglia and innervate target organs, releasing norepinephrine.
Topic: Renal Physiology
Subtopic: Glomerular Filtration Rate (GFR)
Keyword Definitions:
- GFR (Glomerular Filtration Rate): The volume of plasma filtered by the glomeruli per minute, indicating kidney function.
- Freely Filtered: A substance that passes easily through the glomerular filtration barrier without restriction.
- Freely Reabsorbed: Substances taken back into the bloodstream from the renal tubules.
- Secretion: Process by which substances are actively transported from the blood into the tubular fluid.
Lead Question - 2013
All should be features of a substance to measure GFR, except?
a) Freely reabsorbed
b) Freely filtered across glomerulus membrane
c) Not secreted by kidney
d) None
Answer and Explanation:
The correct answer is a) Freely reabsorbed. To accurately measure GFR, a substance must be freely filtered and neither reabsorbed nor secreted by the tubules. Substances like inulin are ideal because they meet these criteria. Reabsorption would lead to underestimation of GFR, making option a incorrect for GFR measurement.
Guessed Questions for NEET PG:
1. Inulin is used to measure GFR because it is:
a) Secreted
b) Reabsorbed
c) Neither reabsorbed nor secreted
d) Metabolized
Explanation: The correct answer is c) Neither reabsorbed nor secreted. Inulin is ideal for measuring GFR as it is freely filtered and neither reabsorbed nor secreted by the renal tubules, allowing accurate assessment of filtration.
2. Creatinine clearance is used to estimate:
a) Tubular secretion
b) GFR
c) Renal blood flow
d) Urine concentration
Explanation: The correct answer is b) GFR. Creatinine clearance approximates GFR because creatinine is freely filtered and only minimally secreted, offering a practical estimate despite slight overestimation.
3. A substance to measure GFR should be:
a) Protein-bound
b) Freely filtered
c) Partially metabolized
d) Actively secreted
Explanation: The correct answer is b) Freely filtered. Substances like inulin are ideal for GFR measurement as they are freely filtered across the glomerular membrane and not metabolized or bound to proteins.
4. Which of the following overestimates GFR?
a) Inulin clearance
b) Creatinine clearance
c) Urea clearance
d) PAH clearance
Explanation: The correct answer is b) Creatinine clearance. Creatinine clearance slightly overestimates GFR because a small amount of creatinine is secreted by renal tubules, increasing measured clearance.
5. Ideal GFR marker should not be:
a) Reabsorbed
b) Secreted
c) Freely filtered
d) Metabolized
Explanation: The correct answer is a) Reabsorbed. A GFR marker must not be reabsorbed, or else its clearance will be underestimated, leading to inaccurate assessment of kidney filtration function.
6. Urea clearance is not ideal for GFR measurement because:
a) It is protein-bound
b) It is actively secreted
c) It is reabsorbed in tubules
d) It is metabolized
Explanation: The correct answer is c) It is reabsorbed in tubules. Urea undergoes tubular reabsorption, making its clearance unreliable for accurate GFR measurement compared to inulin or creatinine.
7. Why is PAH clearance used to measure renal plasma flow (RPF)?
a) Completely filtered
b) Both filtered and secreted
c) Reabsorbed
d) Metabolized
Explanation: The correct answer is b) Both filtered and secreted. PAH is nearly completely extracted from plasma by glomerular filtration and tubular secretion, making its clearance a good estimate of RPF.
8. Glomerular filtration is driven by:
a) Active transport
b) Osmosis
c) Hydrostatic and oncotic pressure differences
d) Endocytosis
Explanation: The correct answer is c) Hydrostatic and oncotic pressure differences. GFR depends on the balance of hydrostatic pressure in glomerular capillaries and oncotic pressure in plasma.
9. A decrease in GFR is seen in:
a) Hypervolemia
b) Hypotension
c) Increased glomerular capillary pressure
d) Low plasma oncotic pressure
Explanation: The correct answer is b) Hypotension. Low systemic blood pressure reduces glomerular hydrostatic pressure, thereby decreasing GFR, potentially leading to renal dysfunction.
10. An ideal substance to measure GFR should have:
a) High protein binding
b) Minimal plasma concentration
c) Rapid renal metabolism
d) No tubular secretion or reabsorption
Explanation: The correct answer is d) No tubular secretion or reabsorption. This ensures the substance's clearance reflects true glomerular filtration without interference, allowing accurate GFR calculation.
Topic: Renal Physiology
Subtopic: Renal Blood Flow and Glomerular Filtration
Keyword Definitions:
- Renal Blood Flow (RBF): The volume of blood delivered to the kidneys per unit time, crucial for filtration and waste removal.
- Glomerular Filtration Rate (GFR): The rate at which plasma is filtered in the glomeruli, reflecting kidney function.
- Autoregulation: The kidney’s ability to maintain constant RBF and GFR despite fluctuations in systemic blood pressure.
Lead Question - 2013
Renal blood flow is ?
a) 1-1.5 L/min
b) 1.5-2 L/min
c) 2-2.5 L/min
d) 2.5-3 L/min
Answer and Explanation:
Correct answer is c) 2-2.5 L/min. In a healthy adult, approximately 20-25% of cardiac output, or around 1200 mL/min (1.2 L/min) of plasma, passes through the kidneys. Given hematocrit, total renal blood flow is about 2-2.5 liters per minute, essential for effective filtration and maintaining homeostasis.
Guessed Questions for NEET PG:
1. What percentage of cardiac output is renal blood flow?
a) 5-10%
b) 15-20%
c) 20-25%
d) 30-35%
Explanation: Correct answer is c) 20-25%. The kidneys receive about 20-25% of cardiac output, facilitating efficient filtration and removal of waste products to maintain internal homeostasis.
2. Renal blood flow autoregulation helps maintain:
a) Constant urine output
b) Stable glomerular filtration rate
c) Varying plasma protein levels
d) Invariable blood pressure
Explanation: Correct answer is b) Stable glomerular filtration rate. Autoregulation keeps GFR stable over a wide range of systemic blood pressures, ensuring efficient waste filtration without damage to nephrons.
3. Which structure primarily regulates renal blood flow?
a) Loop of Henle
b) Afferent and efferent arterioles
c) Collecting ducts
d) Bowman's capsule
Explanation: Correct answer is b) Afferent and efferent arterioles. These control renal blood flow by adjusting their tone, regulating glomerular pressure and filtration rate.
4. Decreased renal perfusion triggers:
a) Decreased renin release
b) Increased renin release
c) Decreased angiotensin II
d) Increased sodium excretion
Explanation: Correct answer is b) Increased renin release. Reduced renal blood flow activates the renin-angiotensin-aldosterone system to maintain blood pressure and perfusion.
5. High renal blood flow is essential for:
a) Muscle contraction
b) Oxygen transport
c) Waste filtration
d) Hormone production
Explanation: Correct answer is c) Waste filtration. High renal blood flow ensures effective filtration of plasma to remove metabolic waste and maintain fluid-electrolyte balance.
6. Which condition decreases renal blood flow?
a) Hypertension
b) Hypotension
c) Hypervolemia
d) Exercise
Explanation: Correct answer is b) Hypotension. Low systemic blood pressure reduces renal perfusion, risking acute kidney injury and impaired filtration.
7. An increase in renal blood flow leads to:
a) Decreased GFR
b) Increased GFR
c) Constant GFR
d) Urinary retention
Explanation: Correct answer is b) Increased GFR. Increased blood flow raises glomerular hydrostatic pressure, increasing the rate of filtration unless autoregulation compensates.
8. Measurement of renal blood flow helps assess:
a) Cardiac output
b) Liver function
c) Kidney perfusion
d) Lung capacity
Explanation: Correct answer is c) Kidney perfusion. Measuring renal blood flow evaluates kidney health, detecting conditions like ischemia or vascular obstruction.
9. Which technique measures renal plasma flow?
a) Inulin clearance
b) PAH clearance
c) Creatinine clearance
d) Urea clearance
Explanation: Correct answer is b) PAH clearance. Para-aminohippuric acid is almost completely cleared from plasma, making its clearance an accurate measure of effective renal plasma flow.
10. Low renal blood flow may cause:
a) Polyuria
b) Oliguria
c) Normal urine output
d) Excess filtration
Explanation: Correct answer is b) Oliguria. Insufficient blood flow reduces GFR, leading to decreased urine production and potential accumulation of waste products.
Topic: Renal Physiology
Subtopic: Sodium Reabsorption in Proximal Tubule
Keyword Definitions:
- Proximal Tubule: First segment of the nephron where most reabsorption of solutes and water occurs.
- Na+-K+-ATPase: An active transporter located at the basolateral membrane of tubular cells, pumping sodium out into interstitium.
- Cotransport: Simultaneous transport of sodium and other solutes like glucose or amino acids across the luminal membrane.
Lead Question - 2013
The primary active step for sodium reabsorption in the proximal tubule involves:
a) Sodium-glucose cotransport across the luminal membrane
b) Sodium/hydrogen ion countertransport across the luminal membrane
c) Sodium transport via the Na+-K+-ATPase at the basolateral membrane
d) Sodium-amino acid cotransport across the luminal membrane
Answer and Explanation:
Correct answer is c) Sodium transport via the Na+-K+-ATPase at the basolateral membrane. The Na+-K+-ATPase actively pumps sodium out of proximal tubular cells into the interstitial space, creating a gradient that drives passive sodium reabsorption from the tubular lumen. This is the primary active mechanism driving overall sodium reabsorption.
Guessed Questions for NEET PG:
1. Sodium reabsorption in the proximal tubule is mainly driven by:
a) Passive diffusion
b) Na+-K+-ATPase pump
c) Osmosis
d) Sodium channels
Explanation: Correct answer is b) Na+-K+-ATPase pump. Sodium reabsorption relies primarily on active extrusion of sodium from the tubular cells to the interstitial space by Na+-K+-ATPase, establishing the necessary gradient.
2. Which transporter facilitates sodium reabsorption along with glucose?
a) Na+-Cl- symporter
b) Sodium-glucose cotransporter
c) Na+-K+-ATPase
d) Aquaporin
Explanation: Correct answer is b) Sodium-glucose cotransporter. This transporter reabsorbs sodium coupled with glucose from the tubular lumen into the proximal tubular cell.
3. Sodium reabsorption in the proximal tubule is approximately:
a) 10%
b) 25%
c) 65%
d) 90%
Explanation: Correct answer is c) 65%. Around 65% of filtered sodium is reabsorbed in the proximal tubule, driven primarily by Na+-K+-ATPase activity.
4. Clinical implication of defective Na+-K+-ATPase in proximal tubule:
a) Hypertension
b) Reduced sodium reabsorption
c) Increased glucose reabsorption
d) Polyuria
Explanation: Correct answer is b) Reduced sodium reabsorption. Dysfunction of the Na+-K+-ATPase reduces the sodium gradient, impairing sodium reabsorption and potentially causing electrolyte imbalance.
5. Role of Sodium-Hydrogen Exchanger in proximal tubule:
a) Na+ reabsorption only
b) Acid-base balance and Na+ reabsorption
c) Water transport
d) Glucose reabsorption
Explanation: Correct answer is b) Acid-base balance and Na+ reabsorption. The exchanger facilitates Na+ reabsorption while secreting H+, aiding pH regulation.
6. Sodium reabsorption in the proximal tubule contributes to:
a) Urine concentration
b) Plasma osmolality maintenance
c) Water excretion
d) Electrolyte loss
Explanation: Correct answer is b) Plasma osmolality maintenance. Sodium reabsorption regulates plasma osmolality and volume, critical for blood pressure and homeostasis.
7. Major energy source for sodium reabsorption in proximal tubule:
a) ATP
b) Glucose
c) ADP
d) NADH
Explanation: Correct answer is a) ATP. Na+-K+-ATPase requires ATP to actively pump sodium out of tubular cells.
8. Sodium-amino acid cotransport occurs in:
a) Distal tubule
b) Proximal tubule
c) Collecting duct
d) Loop of Henle
Explanation: Correct answer is b) Proximal tubule. Amino acids are reabsorbed via sodium-coupled cotransporters in the proximal tubule.
9. Excess sodium reabsorption in proximal tubule may lead to:
a) Hypotension
b) Hypernatremia
c) Hypokalemia
d) Polyuria
Explanation: Correct answer is b) Hypernatremia. Overactive sodium reabsorption increases plasma sodium, risking hypernatremia and fluid retention.
10. Inhibiting Na+-K+-ATPase would cause:
a) Increased sodium reabsorption
b) Decreased sodium reabsorption
c) Increased potassium excretion
d) Unaffected GFR
Explanation: Correct answer is b) Decreased sodium reabsorption. Na+-K+-ATPase inhibition reduces sodium extrusion from tubular cells, impairing the sodium gradient necessary for reabsorption.
Subtopic: Glomerular Filtration Rate (GFR) Measurement
Keyword Definitions:
- GFR (Glomerular Filtration Rate): The volume of plasma filtered by the glomeruli per minute; a key indicator of kidney function.
- Serum Creatinine: A blood measurement of creatinine levels, reflecting kidney filtration ability.
- BUN (Blood Urea Nitrogen): Concentration of nitrogen in blood in the form of urea, indirectly related to kidney function.
- PAN (Para-aminohippuric acid): A compound used to estimate renal plasma flow, not GFR.
Lead Question - 2013
Best measure for GFR?
a) Serum creatinine
b) Urine output
c) BUN
d) PAN
Answer and Explanation:
Correct answer is a) Serum creatinine. Serum creatinine is widely used as the best indirect measure of GFR because it is freely filtered by the glomerulus, not significantly reabsorbed or secreted, and reflects kidney function. Though not perfect, it is a simple and commonly available test for GFR estimation.
Guessed Questions for NEET PG:
1. Which is a direct measure of GFR?
a) Inulin clearance
b) Serum creatinine
c) Urine output
d) BUN
Explanation: Correct answer is a) Inulin clearance. Inulin is freely filtered and neither secreted nor reabsorbed, making it the gold standard to directly measure GFR.
2. Elevated serum creatinine indicates:
a) High GFR
b) Low GFR
c) Normal kidney function
d) High urine output
Explanation: Correct answer is b) Low GFR. Elevated serum creatinine signifies impaired filtration due to reduced GFR and kidney dysfunction.
3. Which is NOT a characteristic of ideal GFR marker?
a) Freely filtered
b) Neither reabsorbed nor secreted
c) Metabolized in tubules
d) Non-toxic
Explanation: Correct answer is c) Metabolized in tubules. Ideal GFR markers should not be metabolized to avoid confounding results.
4. PAN clearance primarily estimates:
a) GFR
b) Renal plasma flow
c) Tubular reabsorption
d) Tubular secretion
Explanation: Correct answer is b) Renal plasma flow. PAN (Para-aminohippuric acid) is nearly completely extracted in one pass and estimates renal plasma flow.
5. Urine output as a GFR measure is:
a) Reliable
b) Best measure
c) Variable and indirect
d) Direct measure
Explanation: Correct answer is c) Variable and indirect. Urine output depends on multiple factors, making it unreliable for precise GFR estimation.
6. BUN is influenced by:
a) Only kidney function
b) Hydration, protein intake, and kidney function
c) Just GFR
d) Pancreatic function
Explanation: Correct answer is b) Hydration, protein intake, and kidney function. BUN is nonspecific due to multiple influencing factors.
7. Normal serum creatinine in adults is around:
a) 0.6 - 1.2 mg/dL
b) 2 - 3 mg/dL
c) 4 - 5 mg/dL
d) 5 - 6 mg/dL
Explanation: Correct answer is a) 0.6 - 1.2 mg/dL. Values in this range suggest normal renal function.
8. Inulin clearance is rarely used clinically because:
a) Expensive
b) Difficult procedure
c) Requires continuous infusion
d) All of the above
Explanation: Correct answer is d) All of the above. Inulin clearance is accurate but impractical for routine clinical use.
9. Which increases serum creatinine?
a) Increased muscle mass
b) Dehydration
c) Kidney disease
d) All of the above
Explanation: Correct answer is d) All of the above. Multiple factors affect serum creatinine levels, including muscle mass, hydration, and kidney function.
10. Ideal GFR marker must be:
a) Secreted by tubules
b) Reabsorbed in tubules
c) Only filtered
d) Metabolized in liver
Explanation: Correct answer is c) Only filtered. Markers like inulin are ideal because they are solely filtered, providing accurate GFR measurement.
Topic: Renin-Angiotensin-Aldosterone System (RAAS)
Subtopic: Functions of Angiotensin II
Keyword Definitions:
- Angiotensin II: A potent vasoconstrictor peptide that regulates blood pressure and fluid balance.
- Thirst Stimulation: The process of increasing water intake via hypothalamic centers.
- Aldosterone: A mineralocorticoid hormone that promotes sodium retention in kidneys.
- ADH (Antidiuretic Hormone): Hormone increasing water reabsorption in kidneys.
- Vasodilation: Widening of blood vessels leading to decreased blood pressure.
Lead Question - 2013
Angiotensin II causes all of the following, EXCEPT:
a) Stimulation of thirst
b) Aldosterone secretion
c) Increased ADH secretion
d) Vasodilation
Answer and Explanation:
Correct answer is d) Vasodilation. Angiotensin II is a powerful vasoconstrictor, not a vasodilator. It increases blood pressure by constricting arterioles, stimulates thirst, promotes aldosterone release from the adrenal cortex, and increases ADH secretion to conserve water, thereby helping maintain blood volume and pressure.
Guessed Questions for NEET PG:
1. Angiotensin II is synthesized from:
a) Renin
b) Angiotensinogen
c) Aldosterone
d) ADH
Explanation: Correct answer is b) Angiotensinogen. Renin converts angiotensinogen to angiotensin I, which is then converted to Angiotensin II by ACE.
2. Aldosterone acts primarily on:
a) Distal tubule
b) Proximal tubule
c) Collecting duct
d) Loop of Henle
Explanation: Correct answer is c) Collecting duct. Aldosterone increases sodium reabsorption and potassium excretion in the collecting duct.
3. ADH secretion is stimulated by:
a) Hypovolemia
b) Hypernatremia
c) Angiotensin II
d) All of the above
Explanation: Correct answer is d) All of the above. ADH release is stimulated by low blood volume, high plasma osmolality, and Angiotensin II.
4. Excess angiotensin II can cause:
a) Hypertension
b) Edema
c) Hypotension
d) Polyuria
Explanation: Correct answer is a) Hypertension. Excessive Angiotensin II leads to increased vasoconstriction, raising blood pressure.
5. ACE inhibitors block:
a) Renin release
b) Angiotensinogen synthesis
c) Angiotensin II formation
d) Aldosterone receptors
Explanation: Correct answer is c) Angiotensin II formation. ACE inhibitors block ACE, reducing Angiotensin II levels.
6. Thirst mechanism is controlled by:
a) Adrenal cortex
b) Hypothalamus
c) Kidneys
d) Pituitary gland
Explanation: Correct answer is b) Hypothalamus. Osmoreceptors in the hypothalamus stimulate thirst during dehydration.
7. Clinical effect of ACE inhibitors is:
a) Decreased blood pressure
b) Increased aldosterone
c) Increased vasoconstriction
d) Increased ADH secretion
Explanation: Correct answer is a) Decreased blood pressure. ACE inhibitors block Angiotensin II, causing vasodilation and lowering blood pressure.
8. Angiotensin II acts on adrenal cortex to:
a) Secrete cortisol
b) Secrete aldosterone
c) Secrete ADH
d) Inhibit renin
Explanation: Correct answer is b) Secrete aldosterone. Angiotensin II stimulates aldosterone secretion for sodium and water retention.
9. Angiotensin II effect on arterioles:
a) Vasodilation
b) Vasoconstriction
c) No effect
d) Only affects veins
Explanation: Correct answer is b) Vasoconstriction. Angiotensin II causes arteriolar constriction, raising systemic vascular resistance and blood pressure.
10. Blockade of Angiotensin II leads to:
a) Increased blood volume
b) Lower blood pressure
c) Hyperkalemia
d) All of the above
Explanation: Correct answer is d) All of the above. Inhibiting Angiotensin II lowers BP, reduces aldosterone leading to hyperkalemia, and may reduce blood volume.
Subtopic: Renal Threshold for Glucose
Keyword Definitions:
- Renal Threshold: Plasma concentration level at which a substance begins to appear in urine.
- Glucose: A simple sugar essential for energy production in cells.
- Proximal Tubule: Part of nephron where glucose reabsorption occurs.
- Glycosuria: Presence of glucose in urine, indicating threshold exceeded.
- Plasma Glucose Level: Concentration of glucose in blood plasma measured in mg/dL.
Lead Question - 2013
Normal renal threshold for glucose is at plasma glucose level ?
a) 100 mg/dl
b) 200 mg/dl
c) 300 mg/dl
d) 400 mg/dl
Answer and Explanation:
Correct answer is b) 200 mg/dl. Normally, glucose is completely reabsorbed by the proximal tubule until the plasma glucose level exceeds approximately 180-200 mg/dl. Beyond this threshold, the transport maximum (Tm) is surpassed, resulting in glucose appearing in urine, a condition termed glycosuria.
Guessed Questions for NEET PG:
1. Glycosuria is commonly seen in:
a) Diabetes mellitus
b) Hypertension
c) Anemia
d) Hypothyroidism
Explanation: Correct answer is a) Diabetes mellitus. High plasma glucose levels exceed renal threshold, causing glucose to spill into urine (glycosuria), a key diabetes symptom.
2. The main site of glucose reabsorption in nephron is:
a) Distal tubule
b) Collecting duct
c) Proximal tubule
d) Loop of Henle
Explanation: Correct answer is c) Proximal tubule. Most glucose reabsorption occurs in the proximal tubule via sodium-glucose cotransporters.
3. Transport maximum (Tm) refers to:
a) Maximal rate of substance secretion
b) Maximal rate of substance reabsorption
c) Maximal urine output
d) None of the above
Explanation: Correct answer is b) Maximal rate of substance reabsorption. When plasma concentration exceeds Tm, substance appears in urine.
4. In untreated diabetes mellitus, renal threshold glucose:
a) Decreases
b) Remains normal
c) Exceeded leading to glycosuria
d) Not related
Explanation: Correct answer is c) Exceeded leading to glycosuria. High plasma glucose surpasses threshold, causing glucose to appear in urine.
5. Fanconi syndrome involves defect in:
a) Glucose reabsorption
b) Sodium reabsorption
c) Amino acid reabsorption
d) All of the above
Explanation: Correct answer is d) All of the above. Fanconi syndrome impairs proximal tubule function causing generalized reabsorption defects.
6. Urinary glucose appears when plasma glucose is above:
a) 70 mg/dl
b) 150 mg/dl
c) 200 mg/dl
d) 250 mg/dl
Explanation: Correct answer is c) 200 mg/dl. The renal threshold for glucose is approximately 180–200 mg/dl.
7. Normal fasting plasma glucose level is:
a) 40-70 mg/dl
b) 70-110 mg/dl
c) 110-150 mg/dl
d) 150-200 mg/dl
Explanation: Correct answer is b) 70-110 mg/dl. Normal fasting glucose levels are tightly regulated within this range.
8. In pregnancy, renal glucose threshold:
a) Increases
b) Decreases
c) Remains constant
d) Becomes zero
Explanation: Correct answer is b) Decreases. Due to increased GFR, glucose threshold lowers leading to mild glycosuria.
9. Glycosuria without hyperglycemia suggests:
a) Renal glycosuria
b) Diabetes mellitus
c) Dehydration
d) Hyperthyroidism
Explanation: Correct answer is a) Renal glycosuria. A rare condition where glucose appears in urine despite normal plasma glucose due to tubular defects.
10. Sodium-glucose cotransporter is located in:
a) Collecting duct
b) Distal tubule
c) Proximal tubule
d) Loop of Henle
Explanation: Correct answer is c) Proximal tubule. SGLT2 in the proximal tubule facilitates glucose reabsorption with sodium.
Topic: Renal Physiology
Subtopic: Hyperosmolarity of Renal Medulla
Keyword Definitions:
- Hyperosmolarity: Increased solute concentration in a solution compared to another solution.
- Renal Medulla: Inner region of the kidney responsible for concentration of urine.
- Sodium (Na): Electrolyte crucial for maintaining fluid balance and generating osmotic gradient.
- Osmotic Gradient: Difference in solute concentration that drives water reabsorption in kidneys.
- Countercurrent Mechanism: Physiological process in nephron contributing to medullary hyperosmolarity.
Lead Question - 2013
Hyperosmolarity of renal medulla is due to?
a) K
b) Na
c) Glucose
d) Cl
Answer and Explanation:
Correct answer is b) Na. The hyperosmolarity of the renal medulla is primarily due to sodium and chloride ions accumulating in the interstitial space via active transport in the thick ascending limb of the loop of Henle. This gradient enables water reabsorption from the collecting duct, concentrating the urine effectively.
Guessed Questions for NEET PG:
1. Main site of sodium reabsorption in nephron is?
a) Collecting duct
b) Proximal tubule
c) Loop of Henle
d) Distal tubule
Explanation: Correct answer is b) Proximal tubule. About 65% of filtered sodium is reabsorbed in the proximal tubule through various sodium transporters.
2. Countercurrent multiplication occurs in?
a) Proximal tubule
b) Loop of Henle
c) Distal tubule
d) Collecting duct
Explanation: Correct answer is b) Loop of Henle. Countercurrent multiplication in the loop of Henle generates a high osmotic gradient important for urine concentration.
3. Urea contributes to medullary hyperosmolarity by?
a) Active transport
b) Passive diffusion
c) Active secretion
d) No role
Explanation: Correct answer is b) Passive diffusion. Urea passively diffuses from the collecting duct into the medullary interstitium, contributing to hyperosmolarity.
4. Thick ascending limb of Henle is impermeable to?
a) Water
b) Sodium
c) Chloride
d) Urea
Explanation: Correct answer is a) Water. The thick ascending limb actively transports Na and Cl but is impermeable to water, aiding in osmolarity generation.
5. ADH acts on which part of nephron?
a) Proximal tubule
b) Distal tubule
c) Collecting duct
d) Loop of Henle
Explanation: Correct answer is c) Collecting duct. ADH increases water permeability in the collecting duct, enhancing water reabsorption and concentrating urine.
6. Medullary osmolarity in mOsm/kg is approximately?
a) 100
b) 300
c) 1200
d) 600
Explanation: Correct answer is c) 1200. The inner medulla achieves a high osmolarity (~1200 mOsm/kg) necessary for water reabsorption and urine concentration.
7. The primary pump generating medullary gradient is?
a) Na+/K+ ATPase
b) K+/Cl- cotransporter
c) Glucose transporter
d) Aquaporin
Explanation: Correct answer is a) Na+/K+ ATPase. Active sodium transport out of tubular cells into interstitium drives osmotic gradient generation.
8. Clinical consequence of impaired medullary osmolarity?
a) Polyuria
b) Oliguria
c) Anuria
d) Hematuria
Explanation: Correct answer is a) Polyuria. Inability to concentrate urine due to loss of medullary gradient results in excessive urine production.
9. Hyperosmolarity is essential for?
a) Glomerular filtration
b) Tubular secretion
c) Urine concentration
d) Filtration pressure
Explanation: Correct answer is c) Urine concentration. The osmotic gradient enables water reabsorption, concentrating urine according to body needs.
10. Thick ascending limb reabsorbs Na+ by?
a) Passive diffusion
b) Na-K-2Cl symporter
c) Sodium-amino acid cotransporter
d) Sodium-glucose cotransporter
Explanation: Correct answer is b) Na-K-2Cl symporter. This symporter reabsorbs sodium along with potassium and chloride, playing a key role in medullary osmolarity.
Topic: Acid-Base Balance
Subtopic: Extracellular Buffer Systems
Keyword Definitions:
- Buffer: Substance that resists changes in pH upon addition of acid or base.
- Extracellular Fluid (ECF): Fluid outside cells, including plasma and interstitial fluid.
- Bicarbonate (HCO3-): A major component in the bicarbonate buffering system, neutralizes excess acids.
- Phosphate Buffer: Buffer system more important intracellularly than extracellularly.
- Ammonia: Weak base involved in renal acid-base regulation.
Lead Question - 2013
Most important extracellular buffer ?
a) Phosphate
b) Plasma proteins
c) Ammonia
d) Bicarbonates
Answer and Explanation:
Correct answer is d) Bicarbonates. Bicarbonate buffer system is the most important extracellular buffer. It maintains blood pH within a narrow range by reacting with hydrogen ions to form carbonic acid, which is then converted to CO₂ and water, preventing drastic pH changes essential for normal cellular function.
Guessed Questions for NEET PG:
1. Primary organ regulating bicarbonate concentration?
a) Liver
b) Kidney
c) Lung
d) Pancreas
Explanation: Correct answer is b) Kidney. Kidneys regulate bicarbonate concentration by reabsorbing bicarbonate and excreting hydrogen ions, crucial for acid-base homeostasis.
2. Henderson-Hasselbalch equation relates?
a) pH, pKa, bicarbonate
b) Osmolarity and solute concentration
c) CO₂ pressure and pH
d) pH and protein concentration
Explanation: Correct answer is a) pH, pKa, bicarbonate. It calculates pH based on bicarbonate concentration and CO₂ partial pressure, essential in acid-base physiology.
3. Respiratory compensation corrects?
a) Metabolic acidosis
b) Respiratory alkalosis
c) Metabolic alkalosis
d) None
Explanation: Correct answer is a) Metabolic acidosis. Respiratory system increases ventilation to expel CO₂ and compensate acidosis.
4. In metabolic alkalosis, expected HCO3- level?
a) Decreased
b) Increased
c) Unchanged
d) Zero
Explanation: Correct answer is b) Increased. Metabolic alkalosis causes elevated bicarbonate levels due to acid loss or alkali gain.
5. Which is a volatile acid?
a) Sulfuric acid
b) Hydrochloric acid
c) Carbonic acid
d) Lactic acid
Explanation: Correct answer is c) Carbonic acid. CO₂ from metabolism forms carbonic acid, removable via lungs, making it volatile.
6. Plasma protein buffer works by?
a) Binding hydrogen ions
b) Excreting acids
c) Producing bicarbonate
d) Increasing respiration
Explanation: Correct answer is a) Binding hydrogen ions. Plasma proteins, especially albumin, buffer acids by binding free H+ ions.
7. Main buffer of intracellular fluid?
a) Bicarbonate
b) Phosphate
c) Ammonia
d) Protein
Explanation: Correct answer is d) Protein. Intracellular proteins serve as major buffers by binding hydrogen ions.
8. Normal plasma bicarbonate concentration?
a) 24-28 mEq/L
b) 15-20 mEq/L
c) 30-35 mEq/L
d) 10-15 mEq/L
Explanation: Correct answer is a) 24-28 mEq/L. This range maintains physiological pH in plasma.
9. In respiratory acidosis, cause is?
a) Hypoventilation
b) Hyperventilation
c) Excess bicarbonate
d) Loss of acid
Explanation: Correct answer is a) Hypoventilation. Reduced breathing causes CO₂ accumulation, increasing carbonic acid and lowering pH.
10. Ammonia buffer system mainly operates in?
a) Liver
b) Kidney
c) Lung
d) Plasma
Explanation: Correct answer is b) Kidney. Ammonia is produced and secreted by renal tubular cells, combining with H+ to facilitate acid excretion.