- If the core body temperature of a human rises above normal, which of the following processes would be initiated sequentially for Thermo-regulation?
(1) Peripheral vasodilation, increased rate of respiration, tachycardia.
(2) Peripheral vasoconstriction, increased rate of respiration, bradycardia.
(3) Peripheral vasodilation, decreased rate of respiration, tachycardia.
(4) Peripheral vasodilation, decreased rate of respiration, bradycardia.
Sequential Thermoregulatory Processes When Core Body Temperature Rises
The human body maintains a tightly controlled core temperature around 37°C via a sophisticated homeostatic mechanism. When this temperature rises above normal, the body activates specific responses to cool itself and restore balance. These responses are orchestrated primarily by the hypothalamus.
Key Thermoregulatory Responses to Increased Body Temperature
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Peripheral Vasodilation:
The first and most significant response is the dilation of blood vessels near the skin’s surface. This increases blood flow to the skin, facilitating heat loss through radiation and convection. -
Increased Rate of Respiration:
As part of the heat loss process, respiration may increase. Breathing faster helps release more heat via expiration of warm air and moisture. -
Tachycardia (Increased Heart Rate):
To support increased blood flow to the periphery, the heart rate increases. This ensures more blood circulates near the skin surface for effective heat dissipation.
Why These Responses Occur in This Order
Peripheral vasodilation immediately increases heat transfer from the body core to the external environment. Faster breathing aids in additional heat loss and removal of moisture. Meanwhile, the heart compensates by increasing its rate to maintain adequate circulation during these changes.
Incorrect Options Explained
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Peripheral vasoconstriction would conserve heat, counterproductive during hyperthermia.
-
Decreased respiration rate would hinder heat loss, not promote it.
-
Bradycardia (reduced heart rate) would limit blood flow and reduce cooling efficiency.
Physiological Summary Table
Step Physiological Effect Purpose Peripheral vasodilation Blood vessels widen near skin Increase heat loss via radiation and convection Increased rate of respiration Breathing becomes faster Heat loss through exhaled air Tachycardia (increased heart rate) Heart pumps blood faster Support increased skin blood flow Conclusion
When the core body temperature rises above normal, the body sequentially initiates:
-
Peripheral vasodilation
-
Increased rate of respiration
-
Tachycardia
These processes together optimize heat dissipation and restore normal temperature.
Therefore, the correct answer is:
(1) Peripheral vasodilation, increased rate of respiration, tachycardia. -
