Thermoregulation — MCQs

Q: Which of the following statements about sweat glands is true?

The hypothalamic preoptic nucleus plays a key role in sweating.. ***The hypothalamic preoptic nucleus plays a key role in sweating.*** - The **hypothalamic preoptic nucleus** is the primary thermoregulatory center in the brain, integrating temperature signals and initiating responses such as sweating to maintain **homeostasis**. - Its activation leads to the stimulation of sympathetic cholinergic nerves that innervate the **eccrine sweat glands**, driving sweat production. *Sweat glands are most numerous on the back and least on the sole.* - **Eccrine sweat glands** are most numerous on the **palms, soles**, and forehead, areas critical for grip and fine motor control. - The back has a moderate density of sweat glands, but not the highest, and the soles have one of the highest densities. *Palm and sole sweat glands are the last to appear.* - **Palm and sole sweat glands** are among the first to develop during fetal development, appearing around the **4th gestational month**. - Other sweat glands, such as those on the trunk and limbs, develop later. *Sweat ducts produce hypotonic sweat.* - Sweat is initially **isotonic** as it is formed by the secretory coil of the gland. - As sweat passes through the sweat duct, **sodium and chloride** are reabsorbed, making the final sweat secreted onto the skin surface **hypotonic**.

Q: The maximum allowable sweat rate during intense physical exercise for a healthy adult is approximately:

2.5 ltrs. ***2.5 ltrs*** - A healthy adult's body can typically **cool itself effectively** through sweating up to an average rate of **2.5 liters per hour** during intense physical exercise. - This rate balances **effective thermoregulation** with the body's capacity to replenish fluids and electrolytes to maintain **homeostasis**. *3.5 ltrs* - While individuals can sweat at rates exceeding 2.5 L/hr, consistently higher rates like **3.5 L/hr** over prolonged periods of intense exercise would put a significant strain on the body's **fluid balance** and electrolyte regulation, increasing the risk of **dehydration** and heat-related illness. - Such rates are often seen in **elite athletes** under extreme conditions and are not a sustainable maximum for general healthy adults. *21 ltrs* - A sweat rate of **21 liters per hour** is physiologically impossible and would lead to immediate, severe, and life-threatening **dehydration**. - The human body simply cannot produce sweat at this volume nor could it sustain such a rapid fluid loss. *4.5 ltrs* - Sweating at **4.5 liters per hour** is an extremely high rate that would be difficult to sustain and would rapidly lead to **severe dehydration** and **electrolyte imbalances** in virtually any individual. - This rate is far beyond what the body can safely manage during prolonged intense exercise without rapid and aggressive fluid replenishment.

Practice by Chapter

Heat Production and Loss

Practice Questions

Temperature Sensing Mechanisms

Practice Questions

Hypothalamic Regulation of Temperature

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Behavioral Thermoregulation

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Fever and Hyperthermia

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Hypothermia

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Exercise and Thermoregulation

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Thermoregulation in Extreme Environments

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Age-Related Changes in Thermoregulation

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Disorders of Thermoregulation

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