Coordination and response
Humans need to be able to respond to changes in the body and in the environment.
The body responds to changes in two ways: through the nervous system . . .
. . . and through the endocrine (or hormonal) system.
For more details see our section on the Endocrine System
Some responses – for instance, swallowing, blinking, and controlling the amount of fluid in the body – are taken care of automatically, without any thought. Other responses – such as standing up, walking, and raising a drink to your lips – require conscious thought and coordination.