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Quiz Chapter 13: Homeostasis and the Human Urinary System

10 questions ยท Form 4 Biology Bab 13: Homeostasis and the Human Urinary System

Question 1 of 10Score: 0

Where are osmoreceptors responsible for detecting changes in blood osmotic pressure located?

Full Question List & Answer Key

Prefer reading to quizzing? All 10 questions are listed below with the answer and explanation under each one.

1. Where are osmoreceptors responsible for detecting changes in blood osmotic pressure located?

  1. A. Carotid sinus
  2. B. Medulla oblongata
  3. C. Hypothalamus
  4. D. Adrenal cortex
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Answer: C

Osmoreceptors in the hypothalamus sense changes in blood solute concentration and adjust thirst and ADH release accordingly.

2. What is the effect of erector muscles relaxing during hot weather?

  1. A. Hairs stand upright to trap a thick layer of still air.
  2. B. Hairs lie flat, preventing air from being trapped next to the skin so heat escapes easily.
  3. C. Sweat production is immediately halted.
  4. D. Subcutaneous fat layers melt away.
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Answer: B

When erector muscles relax, hair follicles lie flat against the skin surface, reducing the trapped insulating layer of still air.

3. A rise in carbon dioxide concentration ($pCO_2$) in the blood leads directly to which physiological change?

  1. A. Increase in blood pH (alkalosis)
  2. B. Decrease in blood pH (acidosis)
  3. C. Inhibition of the respiratory centre
  4. D. Vasoconstriction of pulmonary capillaries
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Answer: B

CO2 reacts with water to form carbonic acid ($H_2CO_3$), which dissociates into $H^+$ ions, lowering blood pH.

4. In hemodialysis, why does the dialysis fluid flow in the opposite direction to the patient's blood (counter-current flow)?

  1. A. To maintain a concentration gradient along the entire length of the membrane for efficient waste removal
  2. B. To prevent blood clot formation inside the artificial dialyzer tubing
  3. C. To increase blood pressure before it re-enters the vein
  4. D. To force red blood cells across the semi-permeable membrane
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Answer: A

Counter-current flow maximizes the concentration gradient between blood and dialysis fluid, ensuring maximum diffusion of urea and excess solutes out of blood.

5. Diabetes insipidus is a disorder caused by an inability of the body to produce or respond to which hormone?

  1. A. Insulin
  2. B. Antidiuretic hormone (ADH)
  3. C. Glucagon
  4. D. Aldosterone
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Answer: B

Deficiency of ADH prevents water reabsorption in distal tubules, causing Diabetes Insipidus characterized by excessive excretion of dilute urine.

6. What primary mechanism allows ultrafiltration to occur within the glomerulus of the nephron?

  1. A. High hydrostatic pressure caused by the afferent arteriole having a larger diameter than the efferent arteriole
  2. B. Active transport of blood proteins across the glomerular membrane
  3. C. Low osmotic pressure in the peritubular capillary network
  4. D. Selective pinocytosis by podocyte epithelial cells
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Answer: A

The difference in diameter between the wider afferent arteriole and narrower efferent arteriole creates high hydrostatic pressure in glomerular capillaries, forcing fluid into Bowman's capsule.

7. Which physiological mechanism contributes to heat loss when body temperature rises?

  1. A. Shivering of skeletal muscles
  2. B. Contraction of erector muscles
  3. C. Evaporation of sweat from skin surface
  4. D. Secretion of adrenaline by adrenal medulla
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Answer: C

Sweat evaporation absorbs latent heat of vaporization from the skin, efficiently cooling the body.

8. When a person consumes a large volume of water, what change occurs in ADH secretion and the resulting urine produced?

  1. A. ADH secretion increases; small volume of concentrated urine
  2. B. ADH secretion decreases; large volume of dilute urine
  3. C. ADH secretion increases; large volume of dilute urine
  4. D. ADH secretion decreases; small volume of concentrated urine
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Answer: B

Excess water lowers blood osmotic pressure, causing the posterior pituitary to release less ADH. The distal tubule becomes less permeable to water, leading to a large volume of dilute urine.

9. What is the primary action of glucagon when blood glucose levels fall below normal?

  1. A. Stimulating liver cells to convert glycogen into glucose
  2. B. Increasing rate of glucose uptake in skeletal muscle cells
  3. C. Promoting storage of excess glucose into fat tissue
  4. D. Inhibiting gluconeogenesis in liver tissues
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Answer: A

Glucagon secreted by pancreatic alpha cells accelerates glycogenolysis (breakdown of glycogen to glucose) in the liver to elevate blood glucose.

10. Where does 100% of useful filtered nutrients, such as glucose and amino acids, get reabsorbed back into the bloodstream under normal healthy conditions?

  1. A. Descending limb of Loop of Henle
  2. B. Proximal convoluted tubule
  3. C. Distal convoluted tubule
  4. D. Collecting duct
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Answer: B

The proximal convoluted tubule actively reabsorbs all filtered glucose and amino acids back into the surrounding peritubular capillaries.

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