Question

in negative feedback, if your body temperature rises above a set point

Answer 1

You'll start to sweat.

Answer 2

Temperature receptors in the skin detect changes in the external temperature. They pass this information to the processing centre in the brain, called the hypothalamus.

The processing centre also has temperature receptors to detect changes in the temperature of the blood. The processing centre automatically triggers changes to the effectors to ensure our body temperature remains constant, at 37°C.

The effectors are sweat glands and muscles.

If we are too hot or too cold, the processing centre sends nerve impulses to the skin, which has two ways to either increase or decrease heat loss from the body's surface.
Cross section of skin showing hairs and the muscles that control them.

Tiny muscles in the skin can quickly pull the hairs upright to reduce heat loss, or lay them down flat to increase heat loss.

Hairs on the skin trap more warmth if they are standing up, and less if they are lying flat. Tiny muscles in the skin can quickly pull the hairs upright to reduce heat loss, or lay them down flat to increase heat loss.

If the body is too hot, glands in the skin secrete sweat onto the surface to increase heat loss by evaporation. This cools the body. Sweat secretion slows when the body temperature returns to normal.