Regulation & Osmoregulation — NEET Biology MCQs with Solutions
Free NEET Biology Regulation & Osmoregulation MCQs with step-by-step solutions (50 questions). Part of Excretory Products and Their Elimination. Practise online on Prepizo — no login needed.
▶ Practise Regulation & Osmoregulation online (free)
Questions with solutions
Q1 — Regulation & Osmoregulation · easy · theory
The hormone that promotes water reabsorption in the kidney (reducing urine volume) is:
A. Adrenaline
B. Thyroxine
C. Insulin
D. ADH (vasopressin) ✓ Correct
Solution: ADH (anti-diuretic hormone) increases water reabsorption from the DCT/collecting duct, concentrating urine.
Q2 — Regulation & Osmoregulation · easy · theory
When the body is dehydrated, ADH secretion ______ and urine becomes ______:
A. Stops; watery
B. Increases; more concentrated (less volume) ✓ Correct
C. Decreases; more dilute
D. Increases; more dilute
Solution: Dehydration → more ADH → more water reabsorbed → concentrated, low-volume urine.
Q3 — Regulation & Osmoregulation · medium · theory
Aldosterone, secreted by the adrenal cortex, acts on the DCT to promote the reabsorption of:
A. Na⁺ (and water) ✓ Correct
B. Proteins
C. Urea
D. Glucose
Solution: Aldosterone increases Na⁺ (and hence water) reabsorption, raising blood volume and pressure.
Q4 — Regulation & Osmoregulation · medium · theory
The Atrial Natriuretic Factor (ANF), released when atrial walls are stretched by high blood pressure, causes:
A. Water retention
B. Vasoconstriction
C. Vasodilation and reduced blood pressure ✓ Correct
D. Increased ADH secretion
Solution: ANF counters the renin-angiotensin system: it dilates vessels and reduces blood volume/pressure.
Q5 — Regulation & Osmoregulation · hard · theory
The renin-angiotensin-aldosterone system responds to a fall in blood pressure/GFR by ultimately:
A. Constricting vessels and increasing Na⁺/water reabsorption to raise blood pressure ✓ Correct
B. Increasing urine output
C. Lowering blood pressure further
D. Reducing sodium reabsorption
Solution: Renin → angiotensin II (vasoconstriction) + aldosterone (Na⁺/water retention) → restores blood pressure and GFR.
Q6 — Regulation & Osmoregulation · hard · theory
The counter-current mechanism in the medulla involves the ______ and the ______ working together:
A. Collecting duct; Bowman's capsule
B. DCT; ureter
C. PCT; glomerulus
D. Loop of Henle; vasa recta ✓ Correct
Solution: The loop of Henle (filtrate) and vasa recta (blood) run counter-current to maintain the medullary osmotic gradient.
Q7 — Regulation & Osmoregulation · easy · numerical
Antidiuretic hormone (ADH) concentrates the urine mainly by:
A. Blocking sodium reabsorption in the proximal tubule
B. Increasing water reabsorption from the distal tubule and collecting duct ✓ Correct
C. Increasing filtration by dilating the afferent arteriole
D. Promoting the loss of large amounts of dilute urine
Solution: ADH raises the water permeability of the DCT and collecting duct, so more water is reabsorbed and a smaller volume of concentrated urine is formed.
Q8 — Regulation & Osmoregulation · easy · numerical
The osmoreceptors that trigger the release of ADH in response to a rise in blood osmolarity are located in the:
A. Hypothalamus ✓ Correct
B. Wall of the atria
C. Adrenal cortex
D. Juxtaglomerular apparatus
Solution: Hypothalamic osmoreceptors detect the increased osmotic concentration (or fall in blood volume) and stimulate ADH release from the neurohypophysis.
Q9 — Regulation & Osmoregulation · easy · numerical
The urge for micturition (passing of urine) is normally triggered when:
A. The collecting duct becomes impermeable to water
B. The glomerulus stops filtering blood into the nephron
C. The kidneys secrete large amounts of renin into the blood
D. Stretch receptors in the wall of the filled urinary bladder are stimulated ✓ Correct
Solution: As the bladder fills, its stretched wall stimulates stretch receptors, sending signals to the CNS that produce the reflex urge to urinate (the micturition reflex).
Q10 — Regulation & Osmoregulation · easy · numerical
ADH is also known by the alternative name:
A. Vasopressin ✓ Correct
B. Angiotensinogen
C. Aldosterone
D. Oxytocin
Solution: Antidiuretic hormone is also called vasopressin because, besides promoting water reabsorption, it can constrict blood vessels and raise blood pressure.
Q11 — Regulation & Osmoregulation · medium · numerical
Arrange the events of the renin–angiotensin–aldosterone mechanism in the correct sequence: (1) angiotensin II stimulates the adrenal cortex to release aldosterone (2) JG cells release renin (3) angiotensin I is converted to angiotensin II (4) renin converts angiotensinogen to angiotensin I.
A. 2 → 4 → 3 → 1 ✓ Correct
B. 4 → 2 → 1 → 3
C. 1 → 2 → 3 → 4
D. 2 → 3 → 4 → 1
Solution: A fall in GFR makes JG cells release renin, which converts angiotensinogen to angiotensin I; this is converted to angiotensin II, which then triggers aldosterone secretion.
Q12 — Regulation & Osmoregulation · medium · numerical
Which set of actions is correctly attributed to angiotensin II?
A. It directly increases water excretion by acting on the collecting duct
B. It causes vasoconstriction and stimulates aldosterone release, raising blood pressure and GFR ✓ Correct
C. It is released by the atria when their walls are over-stretched
D. It dilates blood vessels and inhibits aldosterone, lowering blood pressure
Solution: Angiotensin II is a powerful vasoconstrictor that also stimulates the adrenal cortex to secrete aldosterone; together these actions raise arterial blood pressure and restore GFR.
Q13 — Regulation & Osmoregulation · medium · numerical
Assertion (A): The Atrial Natriuretic Factor (ANF) acts as a check on the renin–angiotensin mechanism. Reason (R): When blood pressure rises, ANF released by the stretched atria causes vasodilation and thereby reduces blood pressure. Choose the correct option.
A. A is false but R is true
B. Both A and R are true and R is the correct explanation of A ✓ Correct
C. A is true but R is false
D. Both A and R are true but R is NOT the correct explanation of A
Solution: ANF released on a rise in blood pressure causes vasodilation and lowers blood pressure, counteracting the pressure-raising renin–angiotensin system; so R correctly explains A.
Q14 — Regulation & Osmoregulation · medium · numerical
In the counter-current mechanism that concentrates urine, the descending and ascending limbs of the loop of Henle behave differently. Which description is correct?
A. The descending limb is permeable to water but the ascending limb is impermeable to water while it transports NaCl ✓ Correct
B. The ascending limb is permeable to water while the descending limb pumps out salt
C. Both limbs are freely permeable to water and to sodium chloride
D. Neither limb allows any movement of water or salt across its wall
Solution: Water leaves the water-permeable descending limb, while the ascending limb is impermeable to water but transports NaCl into the interstitium, building the medullary osmotic gradient.
Q15 — Regulation & Osmoregulation · medium · numerical
A gradient of solute concentration is maintained in the medullary interstitium, increasing from the cortex to the inner medulla. This gradient runs approximately from:
A. A uniform 300 mOsmol/L throughout the cortex and medulla alike
B. 1200 mOsmol/L near the cortex to about 300 mOsmol/L in the inner medulla
C. 100 mOsmol/L near the cortex to about 300 mOsmol/L in the inner medulla
D. 300 mOsmol/L near the cortex to about 1200 mOsmol/L in the inner medulla ✓ Correct
Solution: The medullary osmotic gradient rises from about 300 mOsmol/L in the cortex to roughly 1200 mOsmol/L in the inner medulla, mainly due to NaCl and urea, allowing water to be drawn out of the collecting duct.
Q16 — Regulation & Osmoregulation · medium · numerical
A person who cannot produce enough ADH would be expected to:
A. Pass a small volume of highly concentrated urine
B. Stop forming any glomerular filtrate
C. Reabsorb almost all the filtered water
D. Pass a large volume of very dilute urine ✓ Correct
Solution: Without adequate ADH the collecting duct stays poorly permeable to water, so little water is reabsorbed and copious dilute urine is produced (as in diabetes insipidus).
Q17 — Regulation & Osmoregulation · easy
Which one of the following is produced in the kidneys?
A. Uricase
B. Arginase
C. Rennin
D. Renin ✓ Correct
Solution: Renin is an enzyme produced by the juxtaglomerular (JG) cells of the kidney (Rennin is a gastric enzyme).
Q18 — Regulation & Osmoregulation · easy
Reabsorption of Na+ is controlled by:
A. Vasopressin or ADH
B. Renin
C. Aldosterone ✓ Correct
D. Rennin
Solution: Aldosterone promotes reabsorption of Na+ (and water) from the DCT and collecting tubule.
Q19 — Regulation & Osmoregulation · easy
The reabsorption of water in the kidneys is under the control of a hormone:
A. LH
B. ADH/Vasopressin ✓ Correct
C. ACTH
D. STH
Solution: ADH (vasopressin) increases water reabsorption by making the DCT and collecting duct more permeable to water.
Q20 — Regulation & Osmoregulation · medium
Antidiuretic hormone secretion increases when the hypothalamus is stimulated by:
A. Renin receptors
B. Angiotensin receptors
C. Glucose receptors
D. Osmoreceptors ✓ Correct
Solution: Osmoreceptors are activated by changes in blood volume/ionic concentration and stimulate the hypothalamus to increase ADH release.
Q21 — Regulation & Osmoregulation · medium
The kidneys help regulate acid-base balance by controlling the level of ____ in the blood.
A. HCO3
B. H+
C. 2 and 3 ✓ Correct
D. CO2
Solution: The kidneys regulate acid-base balance by controlling the levels of H+ and HCO3- (bicarbonate) in the blood.
Q22 — Regulation & Osmoregulation · easy
The functioning of the kidneys is efficiently monitored and regulated by hormonal feedback mechanisms involving:
A. JGA only
B. The heart only
C. Hypothalamus, JGA and heart (to certain extent) ✓ Correct
D. Hypothalamus only
Solution: Kidney function is monitored and regulated by the hypothalamus, the juxtaglomerular apparatus (JGA), and, to some extent, the heart.
Q23 — Regulation & Osmoregulation · medium
Osmoreceptors in the body are activated by changes in:
A. Blood volume, body fluid volume and ionic concentration ✓ Correct
B. Body fluid volume but not blood volume
C. Blood volume and body fluid volume
D. Blood volume but not body fluid volume
Solution: Osmoreceptors are activated by changes in blood volume, body fluid volume and ionic concentration of the body fluids.
Q24 — Regulation & Osmoregulation · hard
Which of the following sequences is correct for regulation of kidney function?
A. An excess loss of fluid from body → Osmoreceptors → Hypothalamus → Neurohypophysis → Aldosterone → Water permeability of DCT and CT increases → Prevention of diuresis
B. An excess loss of fluid from body → Osmoreceptors → Hypothalamus → Neurohypophysis → ADH → Increases water permeability of DCT and CT → Prevention of diuresis ✓ Correct
C. An excess loss of fluid from body → osmoreceptor → Hypothalamus → Adenohypophysis → ADH → Increases water permeability of DCT and CT → Prevention of diuresis
D. An excess loss of water from body → Stimulates hypothalamus → Osmoreceptors → Neurohypophysis → ADH → Increases water permeability of DCT and CT → Prevention of diuresis
Solution: Fluid loss activates osmoreceptors, which stimulate the hypothalamus; ADH is released from the neurohypophysis, increasing water permeability of the DCT and CT and preventing diuresis.
Q25 — Regulation & Osmoregulation · easy
Osmoregulation is the function of:
A. None of the above
B. Oxytocin
C. Prolactin
D. Vasopressin (ADH) ✓ Correct
Solution: Vasopressin (ADH) regulates water balance (osmoregulation) by controlling water reabsorption in the kidney.
Q26 — Regulation & Osmoregulation · medium
ADH is synthesised by ______, released by ______ and acts on ______.
A. Hypothalamus, Neurohypophysis, Loop of Henle
B. Hypothalamus, Neurohypophysis, DCT and CT ✓ Correct
C. Hypothalamus, Adenohypophysis, Loop of Henle
D. Hypothalamus, Adenohypophysis, DCT and CT
Solution: ADH is synthesised in the hypothalamus, released by the neurohypophysis (posterior pituitary), and acts on the DCT and collecting tubule.
Q27 — Regulation & Osmoregulation · hard
Which of the following sequences is correct?
A. All of the above ✓ Correct
B. ADH → Constricting effect on blood vessel → B.P. high → Glomerular blood flow more → GFR more
C. An increase in body fluid volume → switch off the Osmoreceptors → suppresses the ADH release
D. Angiotensinogen → Angiotensin I → Angiotensin II → Adrenal cortex → Aldosterone
Solution: All three sequences correctly describe osmoreceptor feedback, the vasoconstrictor effect of ADH, and the renin-angiotensin-aldosterone pathway.
Q28 — Regulation & Osmoregulation · medium
Which of the following factors can activate the JG cells to release renin?
A. A fall in GFR / GBP / GBF ✓ Correct
B. A fall in glomerular blood flow (GBF)
C. A fall in GFR
D. A fall in glomerular blood pressure (GBP)
Solution: A fall in glomerular blood pressure, blood flow, or GFR activates the JG cells to release renin.
Q29 — Regulation & Osmoregulation · medium
Which of the following statements is false?
A. Angiotensin II activates the adrenal cortex to release aldosterone
B. Angiotensin II, being a powerful vasoconstrictor, increases glomerular pressure and thereby GFR
C. Aldosterone promotes reabsorption of Na+ and water from the DCT and CT leading to an increase in B.P. and GFR
D. ANF causes vasoconstriction ✓ Correct
Solution: ANF (Atrial Natriuretic Factor) causes vasodilation, not vasoconstriction, thereby decreasing blood pressure.
Q30 — Regulation & Osmoregulation · medium
RAAS (Renin-Angiotensinogen-Aldosterone System):
A. Are stimulated when ANF is more in blood
B. Is responsible for regulation of kidney function
C. Is triggered when the juxtaglomerular cells of JGA release renin in response to various stimuli
D. Both (1) and (2) are correct ✓ Correct
Solution: RAAS is triggered by the JG cells releasing renin and is responsible for regulating kidney function.