Unit 14: Key Terms
Autonomic nervous system (ANS)
involuntary arm of peripheral nervous system (PNS), also know as visceral motor division, divided into 2 parts, oversees most vital functions
Visceral reflex arcs
ANS manages vital processes through this
Autonomic ganglia
send impulses via other efferent neurons to various target organs, trigger motor response
Somatic motor division
neurons innervate skeletal muscles, leading to voluntary muscle contraction, initiated consciously
Autonomic motor division
neurons innervate smooth muscle cells, cardiac muscle cells, and glands, produce involuntary actions
Two-neuron circuit: Preganglionic neuron
initial efferent neuron, cell body resides within CNS, all axons release acetylcholine
Two-neuron circuit: Postganglionic neuron
cell body resides in the autonomic ganglion in PNS, axons travel to target cells, trigger specific changes (inhibitory or excitatory responses) by releasing either acetylcholine or norepinephrine
Ganglion
cluster of neuronal cell bodies
Sympathetic nervous system
preganglionic axons are usually short and postganglionic axons are usually long
Parasympathetic nervous system
preganglionic parasympathetic axons are long while postganglionic axons are short
Thoracolumbar division
sympathetic nervous system, preganglionic cell bodies originate in thoracic and upper lumbar spinal cord
Sympathetic ganglion
generally located near the spinal cord, preganglionic axons synapse with postganglionic neuron cell bodies, postganglionic axons proceed to target
Sympathetic nervous system
The "fight or flight" division of ANS, prepares the body for emergency situation, has a vital role in the maintenance of homeostasis when the body is engaged in physical work, mediates the body's responses to emotions
Craniosacral division
preganglionic cell bodies located within nuclei of several cranial nerves in brainstem and sacral region of spinal cord
Cranial nerves
innervate structures of head and neck, thoracic viscera, and most abdominal viscera
Sacral nerves
innervate structures within pelvic cavity
Parasympathetic nervous system
"rest and digest" division, role in digestion and in maintaining body's homeostasis at rest, cell bodies of postganglionic neurons are usually located near target organs requires only short axon to make connection
The balance between parasympathetic and sympathetic nervous system
actions of parasympathetic division directly antagonize those of sympathetic division, together, maintain the delicate balance to ensure homeostasis is preserved