Answer:
What makes the sweat glands in the skin secrete more sweat when the body is hot is the brain signaling the sweat glands to secrete sweat to cool the body.
Step-by-step explanation:
The sweat produced by the sweat glands is an important mechanism of body thermoregulation.
The perception of the increase in temperature is captured by specific receptors, which send the information to the central nervous system, specifically to the preoptic area, placed near the hypothalamus. Once the information is processed, the brain sends an efferent response to the effector cells, in this case, the secretory cells of the sweat glands.
The body temperature decreases with sweating because evaporation means that the water in the sweat absorbs heat so that this process occurs, which lowers the body temperature.