Biological Psychology/Anatomy of the Nervous System

Divisions of the Nervous System

Peripheral Nervous System (PNS)

Autonomic Nervous System

The autonomic nervous system controls all "automatic" functions, including visceral, endocrine, and homeostatic functions. It is divided into the sympathetic and parasympathetic nervous systems. The sympathetic system is thought of as the "fight or flight" system. Sympathetic activation involves dilation of the pupils and blood vessels, increased blood pressure, increased respiration, and a sense of "readiness". Stimulants engage this system and have similar effects. In contrast, parasympathetic activation involves contraction of pupils and blood vessels, decreased blood pressure, shallow breathing, and a sense of relaxation. Opiates engage this system. In general, the two systems balance each other, but there are exceptions.