Autonomic (involuntary/visceral) nervous system (ANS)
The ANS is responsible for maintaining the internal environment of the body (homeostasis) by exerting control over many organs and tissues (works in conjunction with endocrine system). It provides motor fibres to smooth muscles, cardiac muscles and glands (effector or target organs). Each efferent pathway consists of two neurons – the preganglionic (presynaptic) neuron in the CNS and the postganglionic (postsynaptic) neuron. The ANS consists of two opposing subsytems – the sympathetic (prepares body for emergency and expending energy) and parasympathetic systems (conserves energy). Some texts consider the ANS as having 3 divisions – the third or enteric systems (associated with the GI tract) does not neatly fit into the existing sympathetic and parasympathetic divisions.