When the human body perceives internal and external stimuli it responds to maintain a stable internal enviroment how does the human body respond to an increase in the environmental temperature?

The body will begin to produce sweat in order to cool the body down.

Similarly, when the temperature decreases, the body will begin to shake because of muscle contractions and this makes the body warm up. When the hair stands up on your arms, it's acting as an insulator to help warm the body.