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Peripheral Nervous System
consists of spinal & cranial nerves, their associated ganglia [groupings of cell bodies], & portions of the ANS
Spinal Nerves
Combined motor-sensory nerve
Spinal Nerves
Dorsal [afferent] sensory nerve fibers or roots
Spinal Nerves
Ventral [efferent] motor fibers or roots
Voluntary Motor System
located in anterior horn of spinal cord gray matter
Autonomic [involuntary] Motor System
located in anterolateral portion of spinal cord gray matter
Dorsal Rami
collection of motor & sensory fiber that eventually go to peripheral structures [skin, muscles, viscera]
- area of skin innervated by sensory fibers of a single dorsal root of a spinal nerve - gives general picture of somatic sensory innervation by spinal segments
muscle group innervated by primary motor neurons of a single ventral root
Cranial Nerves
- 12 paired nerves composed of cell bodies w. fibers that exit from cranial cavity - unlike spinal nerves which always have both afferent sensory & efferent motor fibers, some CNs have ONLY afferent & some only efferent fibers; others have both
Cranial Nerves
- Most CNs are located in specific segments of brain w. EXCEPTION of CN I [Olfactory] & CN II [Optic] - Olfactory nerve located in nasal epithelium - Optic nerve located in retina - CN XI [Accessory] is a spinal nerve, & its efferent fibers migrate upward before exiting the neuroaxis at level of medulla
Autonomic Nervous System
- governs involuntary functions of cardiac muscle, smooth [involuntary] muscle, & glands - divided into 2 components: sympathetic & parasympathetic
Major Neurotransmitter Released By Postganglionic Fibers of SNS
Norepinephrine, & the neurotransmitter released by the preganglionic fibers is Acetylcholine
Neurotransmitter Released @ Both Preganglionic & Postganglionic For PSNS
Sympathetic Nervous System
- increases rate & force of heart contraction - dilates bronchi & bronchioles of lungs - activation of "fight or flight"
Parasympathetic Nervous System
- decreases rate & force of heart contraction - constricts bronchi & bronchioles of lungs - act in localized & discrete regions, it serves to conserve & restore energy stores of body
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