Īctivation of the SNS leads to a state of overall elevated activity and attention: the “fight or flight” response. It contains over 100 million neurons of over 15 morphologies, greater than the sum of all other peripheral ganglia, and is chiefly responsible for the regulation of digestive processes.
The enteric nervous system (ENS) is an extensive, web-like structure that is capable of function independently of the remainder of the nervous system. Generally, the SNS and PNS motor pathways consist of a two-neuron series: a preganglionic neuron with a cell body in the CNS and a postganglionic neuron with a cell body in the periphery that innervates target tissues. The sympathetic nervous system (SNS) and the parasympathetic nervous system (PNS) contain both afferent and efferent fibers that provide sensory input and motor output, respectively, to the central nervous system (CNS). It contains three anatomically distinct divisions: sympathetic, parasympathetic, and enteric. The autonomic nervous system is a component of the peripheral nervous system that regulates involuntary physiologic processes including heart rate, blood pressure, respiration, digestion, and sexual arousal.
