Which of the following statements about thermoregulatory responses to increased heat is correct?

• A. They are controlled exclusively by voluntary muscle activity.
• B. They do not involve the autonomic nervous system.
• C. They are primarily mediated by the parasympathetic nervous division.
• D. They are primarily mediated by the sympathetic nervous division.

Answer: (D)

Verified step by step guidance

1. Understand the concept of thermoregulation: Thermoregulation is the process by which organisms maintain their internal body temperature within a certain range, even when the external environment changes. This involves physiological and behavioral responses.
2. Identify the role of the autonomic nervous system (ANS): The ANS is responsible for involuntary physiological functions, including thermoregulation. It has two main divisions: the sympathetic and parasympathetic nervous systems.
3. Clarify the role of the sympathetic nervous system: The sympathetic nervous system is primarily responsible for the body's 'fight or flight' responses, including thermoregulatory mechanisms like sweating and vasodilation (widening of blood vessels) to dissipate heat.
4. Eliminate incorrect options: Voluntary muscle activity is not the primary mechanism for thermoregulation, and the parasympathetic nervous system is more involved in 'rest and digest' functions rather than heat dissipation. Additionally, thermoregulation does involve the autonomic nervous system, so that option is also incorrect.
5. Conclude with the correct answer: The correct statement is that thermoregulatory responses to increased heat are primarily mediated by the sympathetic nervous division, as it controls processes like sweating and blood flow adjustments to regulate body temperature.