40 past paper MCQs on Homeostasis and the Kidney, from the Homeostasis unit of MDCAT Biology. The year each question appeared is shown where known; tap “Show answer” for the correct option and a short solution.
1.Kidneys perform their osmoregulatory role under the effect of Antidiuretic Hormone, which type of urine is produced in this situation? (UHS MDCAT 2025)
Correct answer: (c) Hypertonic urine with decreased volume
ADH makes the collecting ducts reabsorb more water, so a smaller volume of concentrated, hypertonic urine leaves.
2.The process of osmoregulation refers to: (UHS MDCAT 2025)
Correct answer: (b) The regulation of solute and water movement between an organism and its environment
Osmoregulation is the control of the water and solute balance between the organism and its surroundings.
3.Which type of nephron is responsible for the development of osmotic gradients in the renal medulla? (KMU MDCAT 2025)
Correct answer: (c) Juxtamedullary
Only the juxtamedullary nephrons have loops long enough to build the osmotic gradient of the medulla.
4.Which of the following describes how the distal convoluted tubule contributes to regulation of blood pH in the body? (KMU MDCAT 2025)
Correct answer: (b) Active secretion of hydrogen ions into the filtrate
The distal tubule secretes hydrogen ions into the filtrate, which is how the blood is kept from turning acidic.
5.The sodium potassium pumps in the distal convoluted tubule are activated by: (KMU MDCAT 2025)
Correct answer: (a) Aldosterone
Aldosterone from the adrenal cortex drives the sodium potassium pumps of the distal tubule.
6.If a person drinks excessive amount of water, how does the kidney respond to maintaining osmoregulation? (KMU MDCAT 2025)
Correct answer: (d) Decrease ADH release and increase water excretion
Dilute blood suppresses ADH, the ducts stay impermeable, and the surplus water leaves as dilute urine.
7.The primary function of glomerular capillaries is: (KMU MDCAT 2025)
Correct answer: (c) Filtration of blood from glomerular filtrate
High pressure in the glomerulus forces water and small solutes out of the blood as the filtrate.
8.Hyperparathyroidism may lead to the formation of: (KMU MDCAT 2025)
Correct answer: (a) Calcium phosphate stones
Too much parathyroid hormone frees calcium from the bones, and the excess settles as calcium phosphate stones.
9.Overconsumption of which of the following foods increases the risk of calcium oxalate stone? (SIBA MDCAT 2025)
Correct answer: (a) Leafy vegetables
Spinach and other leafy vegetables are rich in oxalate, which settles with calcium as a stone.
10.Which of the following substances pass through the glomerulus into Bowman's capsule? (SIBA MDCAT 2025)
Correct answer: (a) Glucose
Glucose is small enough to be filtered; cells and plasma proteins are held back.
11.The water content of human kidney is regulated by ADH. Which of the following gland is involved in its secretion process? (SIBA MDCAT 2025)
Correct answer: (b) Pituitary gland
Antidiuretic hormone is released from the posterior lobe of the pituitary.
12.Osmotic gradient of inner medulla of kidney is increased by: (SZABMU MDCAT 2025)
Correct answer: (a) Urea
Urea diffusing out of the collecting duct is what makes the inner medulla so concentrated.
13.The hormone, when overproduced can lead to hypercalcemia and stone formation is: (SZABMU MDCAT 2025)
Correct answer: (c) Parathyroid hormone
Excess parathyroid hormone frees calcium from bone, and the surplus settles in the kidney as stones.
14.Additional capillaries present in the juxtamedullary nephrons to form a loop of vessels are: (SZABMU MDCAT 2025)
Correct answer: (c) Vasa recta
The vasa recta are the straight capillaries that follow the long loops of the juxtamedullary nephrons.
15.How do the kidneys contribute to maintain normal blood calcium level? (SZABMU MDCAT 2025)
Correct answer: (b) By reabsorbing calcium and activating vitamin D
The kidney reabsorbs calcium from the filtrate and makes vitamin D active so the gut absorbs more.
16.Osmoreceptors that detect the osmotic pressure of blood are primarily located in the: (SZABMU MDCAT 2025)
Correct answer: (c) Hypothalamus
The osmoreceptors of the hypothalamus watch the osmotic pressure of the blood and call for ADH.
17.A desert mammal faces severe dehydration in a hot sunny day. Which internal condition would lead to secretion of ADH? (NUMS MDCAT 2024)
Correct answer: (a) High osmotic pressure of blood
Losing water concentrates the blood, and the osmoreceptors answer that by calling for ADH.
18.Hormone secreted in bulk due to decreased water content of blood is: (NUMS MDCAT 2023)
Correct answer: (a) Anti-Diuretic Hormone (ADH)
Concentrated blood is sensed by the hypothalamus, which calls for antidiuretic hormone.
19.The target cells of this hormone are present in kidney tubules: (PMC MDCAT 2022)
Correct answer: (a) Aldosterone
Aldosterone acts on the distal tubule of the nephron to reabsorb sodium.
20.The mechanism of regulation, generally between organism and Its environment, of solutes and the gain and the loss of water is called? (PMC MDCAT 2022)
Correct answer: (c) Osmoregulation
Controlling the water and solute balance with the surroundings is osmoregulation.
21.The active uptake of sodium in the ascending limb or thick loop of Henle is promoted by the action of: (PMC MDCAT 2020)
Correct answer: (a) Aldosterone
Aldosterone drives the sodium pumps of the nephron.
22.The excretion of hypertonic urine in humans is associated best with the: (PMC MDCAT 2020)
Correct answer: (c) Loop of Henle
The loop of Henle builds the salt gradient of the medulla that lets water be drawn from the collecting duct.
23.The capillaries of glomerulus rejoin to form an _______. (UHS MDCAT 2018)
Correct answer: (a) Efferent arteriole
The glomerular capillaries gather again into the efferent arteriole, which is narrower than the afferent one.
24.When filtration is completed the waste products through distal tube of Nephrons empties to: (UHS MDCAT 2018)
Correct answer: (b) Collecting Tubules
The distal tubule empties into the collecting duct, which carries the urine down through the medulla.
25._________ hormone is released from the posterior lobe of the pituitary gland. (UHS MDCAT 2018)
Correct answer: (d) Antidiuretic hormone
The posterior pituitary releases antidiuretic hormone and oxytocin.
26.The hormone which controls the uptake of Sodium ions in kidney and its maintenance in blood plasma is: (UHS MDCAT 2018)
Correct answer: (b) Aldosterone Hormone
Aldosterone drives the sodium pumps of the distal tubule.
27.Keeping correct balance of ions and water in our body is called as: (UHS MDCAT 2018)
Correct answer: (b) Osmoregulation
Keeping the water and solute balance right is osmoregulation.
28.Blood solute potential is controlled by the following hormone. (UHS MDCAT 2018)
Correct answer: (d) Vasopressin
Vasopressin, that is antidiuretic hormone, sets how much water the kidney returns to the blood.
29.Blood leaves the Bowman’s capsule by: (UHS MDCAT 2017)
Correct answer: (c) Efferent arterioles
The glomerular capillaries gather into the efferent arteriole.
30.The mechanism of regulation, generally between organisms and its environment, of (UHS MDCAT 2017)
Correct answer: (b) Osmoregulation
Controlling the water and solute balance with the surroundings is osmoregulation.
31.End-stage renal failure is called: (UHS MDCAT 2017)
Correct answer: (c) Uremia
Uraemia is the accumulation of urea and other wastes when the kidneys fail.
32.Which structure receives about 20% of total blood and has a weight less than 1% of the total body: (UHS MDCAT 2017)
Correct answer: (c) Kidney
The kidneys take about a fifth of the cardiac output though they weigh less than a hundredth of the body.
33.Bowman’s capsule continues as extensively convoluted portion known as: (UHS MDCAT 2016)
Correct answer: (b) Proximal convoluted tubules
The Bowman capsule leads into the proximal convoluted tubule.
34.A hormone released from posterior pituitary lobe acts to be actively transport water from filtrate is collecting tubules back to kidney is shown as: (UHS MDCAT 2016)
Correct answer: (b) Antidiuretic hormone
Antidiuretic hormone makes the collecting duct permeable, so water returns to the blood.
35.Those nephrons which are present along the border of the cortex and medulla are called: (UHS MDCAT 2015)
Correct answer: (a) Juxtamedullary nephrons
The juxtamedullary nephrons sit at the border and send their long loops into the medulla.
36.When water is in short supply, increased water retention occurs through the: (UHS MDCAT 2015)
Correct answer: (c) Juxtamedullary nephrons
Only their long loops can build the gradient that lets water be drawn back.
37.In nephrons, counter-current multiplier occurs at: (UHS MDCAT 2015)
Correct answer: (a) Loop of Henle
The two limbs of the loop of Henle work against each other to multiply the gradient.
38.Ascending loop of Henle does not allow outflow of: (UHS MDCAT 2015)
Correct answer: (d) Water
The ascending limb is impermeable to water; it pumps out salt instead.
39.A larger quantity of dilute urine is produced in diabetes insipidus. This disease is due to the deficiency of: (UHS MDCAT 2015)
Correct answer: (a) Antidiuretic Hormone
Without antidiuretic hormone the collecting duct stays impermeable and a great deal of dilute urine is passed.
40.Water and sodium ions are reabsorbed in: (UHS MDCAT 2015)
Correct answer: (d) Proximal Convoluted Tubule & Collecting Duct
Most water and sodium return in the proximal tubule, and the rest under hormonal control in the collecting duct.