Chapter 11Peripheral Nervous System

Peripheral Nervous System

• Cranial nerves arising from the brain• Connect to the skin and skeletal muscles• Connect to viscera(organs)

• Spinal nerves arising from the spinal cord• Connect to the skin and skeletal muscles• Connecting to viscera(organs)

Structure of a Peripheral Nerve

Nerve Fiber Classification

• Sensory Nerves – conduct impulses into CNS• Motor Nerves – conduct impulses to muscles or glands• Mixed Nerves – contain both sensory nerve fibers and motor nerve fibers; most nerves

Cranial Nerves

Cranial Nerves I and II

Olfactory (I)•sensory •smell

Optic (II)•sensory •vision

Cranial Nerves III and IV

Trochlear (IV)• primarily motor• motor impulses to muscles that move the eyes

Oculomotor (III)• primarily motor• motor impulses to muscles that

• raise eyelids• move the eyes• focus lens•adjust light entering eye

Cranial Nerve V

Trigeminal (V)• mixed (both)• opthalmic division

• sensory from surface of eyes, tear glands, scalp, forehead, and upper eyelids

• maxillary division• sensory from upper teeth, upper gum, upper lip, palate, and skin of face

• mandibular division• sensory from scalp, skin of jaw, lower teeth, lower gum, and lower lip• motor to muscles of mastication and muscles in floor of mouth

Muscles of Mastication

Cranial Nerves VI and VII

Abducens (VI)• primarily motor• motor impulses to muscles that move the eyes

Facial (VII)• mixed (both)• sensory from taste receptors• motor to muscles of facial expression, tear glands, and salivary glands

Muscles of Facial Expression

Cranial Nerves VIII and IX

Vestibulocochlear (VIII)• aka Auditory • sensory• sensory from equilibrium receptors of ear (balance)• sensory from hearing receptors

Glossopharyngeal (IX)• mixed (both)• sensory from pharynx, tonsils, tongue, and carotid arteries• motor to salivary glands and muscles of pharynx

Cranial Nerve X

Vagus (X)• mixed (both)• motor to muscles of speech and swallowing• motor to viscera of thorax and abdomen• sensory from pharynx, larynx, esophagus, and viscera of thorax and abdomen

Cranial Nerves XI and XII

Accessory (XI)•Aka Spinal Accessory •primarily motor• motor to muscles of soft palate, pharynx, larynx, neck (sternocleidomastoid), and back (trapezius)

Hypoglossal (XII)• primarily motor• motor to muscles of the tongue

Spinal Nerves

• mixed nerves• 31 pairs

• 8 cervical (C1 to C8)• 12 thoracic (T1 to T12)• 5 lumbar (L1 to L5)• 5 sacral (S1 to S5)• 1 coccygeal (Co)

Dermatome

• an area of skin that the sensory nerve fibers of a particular spinal nerve innervate

Cervical Plexus

Nerve plexus – complex networks formed by anterior branches of spinal nerves; fibers of various spinal nerves are sorted and recombined

Cervical Plexus• C1-C4• lies deep in the neck• supply muscles and skin of the neck• contribute to phrenic nerve

Brachial Plexus

• C5-T1• lies deep within shoulders• musculocutaneous nerves

• biceps brachii; brachialis• ulnar nerves

• “funny bone”• flexor carpi ulnaris

• median nerves• flexor carpi radialis

•radial nerves• posterior muscles• triceps brachii• extensors

• axillary nerves• deltoid

Muscles That Move the Forearm

Muscles That Move the Hand

Lumbosacral Plexus

• T12 – S5• obturator nerves

• supply adductors of thighs

• femoral nerves• supply muscles and skin of quads and sartorius

• tibial nerves•supply posterior leg muscles; hams, calves

• sciatic nerves• longest and largest nerve of the body

Muscles That Move the Thigh

Muscles That Move the Leg

Muscles That Move the Foot

Autonomic Nervous System

• functions without conscious effort• controls visceral activities• regulates smooth muscle, cardiac muscle, and glands

Two Divisions• sympathetic – prepares body for fight or flight situations• parasympathetic – prepares body for resting and digesting activities

Sympathetic Division

Parasympathetic Division

Control of Autonomic Activity

• Controlled largely by CNS• Medulla oblongata regulates cardiac, vasomotor and respiratory activities• Hypothalamus regulates visceral functions• Cerebral cortex control emotional responses