HKDSE · DSE Biology
DSE Biology: Human Physiology: Regulation and Control (Elective) — Practice Questions & Answers
How the human body keeps its internal conditions stable through nervous and hormonal coordination, regulates water and temperature, and reproduces.
432 practice questions available for this topic — here are 10 with full answers and explanations.
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Practice questions with answers
1
Multiple choice · Medium
During recovery from exercise, the sodium concentration of a drink affects water balance mainly by influencing:
- the osmotic concentration of the body fluids and hence ADH secretion
- the rate of cellular respiration in muscle
- the breathing rate
- the speed of nerve impulses
Tap an answer to check it.
WhySodium sets the osmotic concentration of body fluids, which controls ADH secretion.
2
Multiple choice · Hard
A drink containing no sodium leads to a large urine output because it:
- lowers plasma osmolarity, suppressing ADH and reducing water reabsorption
- raises plasma osmolarity, increasing ADH secretion
- increases the filtration of plasma proteins
- directly damages the collecting duct
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WhyLowering plasma osmolarity suppresses ADH and reduces water reabsorption.
3
Multiple choice · Easy
Which structure of the nephron is the main site of ADH-controlled water reabsorption?
- Collecting duct
- Glomerulus
- Bowman's capsule
- Loop of Henle ascending limb
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WhyADH increases the water permeability of the collecting duct.
4
Fill in the blank · Medium
ADH is secreted from the posterior gland when blood osmotic concentration rises.
Answer:
pituitary
WhyThe posterior pituitary releases ADH.
5
Fill in the blank · Easy
ADH increases the permeability of the collecting duct to , increasing its reabsorption.
Answer:
water
WhyADH opens aquaporins so water is reabsorbed.
6
Fill in the blank · Hard
A sodium-rich drink helps athletes retain water because the sodium maintains the concentration of the body fluids.
Answer:
osmotic / solute / salt
WhyMaintaining osmotic concentration keeps ADH active and conserves water.
7
Multiple choice · Medium
If both the surrounding temperature and humidity are very high, vigorous exercise is dangerous because:
- sweat cannot evaporate, so body heat is not lost and core temperature rises
- the body loses too much heat and cools down
- sweating increases and cools the body too much
- cellular respiration stops completely
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WhySweat cannot evaporate, so body heat is not lost and core temperature rises.
8
Multiple choice · Hard
During thermoregulation in the heat, the combined effect of vasodilation and sweating is to:
- increase heat loss from the body surface to restore normal core temperature
- reduce heat loss to conserve energy
- raise the set point of the hypothalamus
- increase metabolic heat production
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WhyBoth responses raise heat loss to restore normal core temperature.
9
Multiple choice · Easy
Which receptor and control centre detect and regulate a rise in core body temperature?
- Thermoreceptors and the hypothalamus
- Chemoreceptors and the medulla
- Photoreceptors and the cerebrum
- Baroreceptors and the cerebellum
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WhyThermoreceptors send signals to the hypothalamus.
10
Fill in the blank · Medium
A dangerous rise in core body temperature when heat loss fails is called heat .
Answer:
stroke / exhaustion
WhyHeat stroke results when thermoregulation is overwhelmed.
Key terms in Human Physiology: Regulation and Control (Elective)
Homeostasis: The maintenance of a stable internal environment within narrow limits in the body.
Negative feedback: A control mechanism in which a change triggers a response that reverses the change.
Nervous system: The system of neurons that allows rapid communication and coordination in the body.
Neuron: A specialised cell that transmits electrical impulses in the nervous system.
Synapse: The junction between two neurons where a signal is passed by chemical neurotransmitters.
Reflex action: A rapid automatic response to a stimulus that does not involve conscious thought.
Reflex arc: The nerve pathway of a reflex action from receptor to effector.
Receptor: A cell or organ that detects a stimulus and produces a nerve impulse.
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