Somatic Nervous System                                     The Autonomic Nervous System

Both Sensory and motor neurons                                   Motor neurons

Input from the special senses, proprioreceptors,             General visceral sensory neurons
and general somatic receptors

Operates with conscious control                                     Usually without conscious control

Effect of motor neurons is excitation                                 Effects can be excitatory or inhibitory

Single motor neuron                                                         Two motor neurons in series

Releases Acetylcholine at synapses                                     Releases acetylcholine or
                                                                                            norepinephrine at synapses
 
 

Sympathetic N.S.                                                         Parasympathetic N. S.
 

Originates in the thoracic and lumbar segements                 Originates in the brain stem and sacral
of the spinal cord : Thoracolumbar system                         segments: Craniosacral system

Synapses near the spinal cord                                             Synapses near visceral effector

Preganglionic neuron synapses with neurons to                     Preganglionic neuron synapses with
several organs                                                                     neurons to a single organ

Effect is wide spread                                                             Effect is local

"Fight-or-Flight" - "E's":                                                         "Feed and Breed" - "SLUD"
emergency, excitement, exercise, embarrassment                     salivation, lacrimation, urination,
                                                                                              defecation

Postganglionic fibers release norepinephrine                             Postganglionic fibers release ACh

Receptors are alpha and beta                                                   Receptors are nicotinic and
                                                                                                muscarinic