Peripheral Nervous System I Composed of Nerves A

Peripheral Nervous System

I. Composed of Nerves A. Bundle of neurons surrounded by connective tissue

B. Classification of nerves 1. Sensory/Afferent – composed entirely of sensory neurons 2. Motor/Efferent – composed entirely of motor neurons 3. Mixed – composed of both sensory and motor neurons

II. Divided into 2 subcomponents A. Somatic and Autonomic Nervous Systems 1. Somatic – voluntary control of skeletal muscles 2. Autonomic – involuntary control of smooth muscle, cardiac muscle, and glands

Somatic Voluntary? Usually Never Skeletal Muscles Glands, smooth muscle, cardiac muscle Acetylcholine – always! Acetylcholine, epinephrine, norepinephrine Effectors Neurotransmitters Autonomic

III. Autonomic Nervous System A. Controls involuntary responses to regulate physiological responses B. Further divided into Sympathetic and Parasympathetic divisions

1. Sympathetic division – “Fight or Flight” a. Nerves originate from center of spinal cord b. Uses epinephrine and norepinephrine as neurotransmitters

c. Response to unusual circumstances – increases activity d. “E” division – exercise, excitement, emergency, embarrassment Sympathetic = Snake

2. Parasympathetic division – “Rest and digest” a. Nerves originate from the brain stem and upper and lower parts of the spinal cord b. Uses acetylcholine as neurotransmitter

c. Conserves energy and handles the usual circumstances d. “D” division – digestion, defecation, diuresis Parasympathetic = Panda

IV. Cranial Nerves A. Peripheral nerves that arise from the brain instead of the spinal cord B. For the most part control parts things from the neck up (vagus nerve is the exception)

I – Olfactory – sensory, smell

II – Optic – sensory, vision

III – Oculomotor – motor, eye muscles – moves eyelids and eyeball, adjusts pupils and lenses

IV – Trochlear, motor, moves eyeballs

V – Trigeminal – sensory for face, motor for chewing

VI – Abducens – motor, moves eyeballs

VII – Facial Sensory – taste Motor - face

VIII – Vestibulocochlear Sensory – balance and hearing

IX – Glossopharyngeal Sensory – taste Motor – pharynx (swallowing)

X – Vagus – sensory & motor, throat and internal organs

XI – Accessory – motor, neck & upper back

XII – Hypoglossal – motor, tongue