The peripheral nervous system connects the central nervous system to the rest of the body and is divided into sensory and motor divisions. It has two main subdivisions: the somatic nervous system which controls voluntary skeletal muscles, and the autonomic nervous system which regulates involuntary functions like digestion. The autonomic nervous system has two divisions - the sympathetic "fight or flight" system and the parasympathetic "rest and digest" system. Reflexes are involuntary responses to stimuli that involve reflex arcs in the spinal cord or brain.