What role does the sympathetic nervous system play in thermoregulation during hypothermia?

• A. Vasodilation of blood vessels
• B. Inducing shivering
• C. Sweating
• D. Increasing heart rate

Answer: (B)

The sympathetic nervous system plays a crucial role in thermoregulation during hypothermia primarily by inducing shivering. Shivering is a physiological response that generates heat through rapid, involuntary muscle contractions. When the body temperature falls below normal levels, the hypothalamus, which acts as the body's thermostat, signals the sympathetic nervous system to activate shivering. This involuntary muscle activity raises the body's temperature by increasing metabolic heat production.

While the sympathetic nervous system does influence other responses such as increased heart rate, which helps in maintaining necessary blood flow during cold exposure, the direct role in thermoregulation during hypothermia is most effectively achieved through shivering. This mechanism is essential for re-establishing normal body temperature and preventing further cold stress.

In contrast, vasodilation of blood vessels would lead to increased blood flow to the skin, promoting heat loss, which is counterproductive in a state of hypothermia. Sweating also serves to cool the body; therefore, it is not a relevant response in cold conditions. Overall, the induction of shivering stands out as the primary protective thermoregulatory response mediated by the sympathetic nervous system during episodes of hypothermia.