Which of the following is an example of feedforward regulation?

Feedforward regulation is a physiological response that anticipates a change in the internal state of the body before it occurs, enabling the body to prepare for or mitigate the effects of that change.

The presence of food triggering salivation is a classic example of feedforward regulation. When food is sensed or anticipated, the salivary glands secrete saliva in preparation for digestion. This anticipatory mechanism enhances the efficiency of the digestive process by ensuring that digestive enzymes are ready when food enters the oral cavity. Salivation in response to the sight or smell of food demonstrates how the body can proactively adjust its physiology to enhance food intake and digestion.

In contrast, the other options involve feedback mechanisms that respond to changes after they have occurred, rather than anticipating them. For instance, the decrease in heart rate after exercise reflects the body's response to reduced physical demand, rather than a preparatory action. Similarly, increases in body temperature due to external heat and the increase in sweating during exercise occur in response to conditions already present, rather than in anticipation of those conditions.