“The peripheral nervous system can also be divided into two major divisions: the somatic nervous system and the autonomic nervous system. Basically, the somatic nervous system is concerned with your awareness of and reactions to the external environment, to the world outside your body. It consists of all the nerves bringing sensory information into your CNS and all the motor nerves going out to skeletal muscles that enable you to move and otherwise react to incoming information.

“By contrast, the autonomic nervous system is concerned with the internal environment, with what’s going on inside your body.”