Question

The temperature yesterday was an uncomfortable 98°F. You unwisely chose to play tennis at noon, counting on your body's internal defenses to protect you against heat exhaustion. How did your body respond to this distress?

Answer 1

Body temperature is regulated by hypothalamus, which sets the normal range of body temperature. The set point, under normal physiological conditions is 37°C. Hypothalamus has two centers which regulate the body temperature:  

a.Heat loss center that is present in preoptic nucleus of anterior hypothalamus.

b.Heat gain center that is situated in posterior hypothalamic nucleus

When body temperature increases, it stimulates the thermoreceptors present in the heat loss center in preoptic nucleus. Now, the heat loss center brings the temperature back to normal by two mechanisms:

1. Promotion of heat loss --- When body temperature increases, heat loss center promotes heat loss from the body by two ways:

i. By increasing the secretion of sweat: When sweat secretion increases, more water is lost from skin along with heat

ii. By inhibiting sympathetic centers in posterior hypothalamus: This causes cutaneous vaso dilatation. Now, the blood flow through skin increases causing excess sweating. It increases the heat loss through sweat, leading to decrease in body temperature.

2. Heat loss center prevents heat production in the body by inhibiting mechanisms involved in heat production, such as shivering and chemical (metabolic) reactions.