What is the process of maintaining a constant internal environment called ?

i guess because there isn't enough love going around. < 3

answer an inhibitory neurotransmitter in the brain;

i took a test for bio that had this question and these were the correct answers, not sure if this is any now lol

the nervous system and the muscular system work together.  

sweat reaches the surface of the skin and evaporates into the air.

muscles underneath the skin relax, causing hair on the skin to lay flat.