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Peripheral Nervous System • Cranial nerves arising from the brain • Somatic fibers connecting to the skin and skeletal muscles • Autonomic fibers connecting to viscera • Spinal nerves arising from the spinal cord • Somatic fibers connecting to the skin and skeletal muscles • Autonomic fibers connecting to viscera 11-42 Structure of a Peripheral Nerve 11-43 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 General somatic efferent fibers • carry motor impulses from CNS to skeletal muscles General somatic afferent fibers • carry sensory impulses to CNS from skin and skeletal muscles General visceral efferent fibers • carry motor impulses away from CNS to smooth muscles and glands General visceral afferent fibers • carry sensory impulses to CNS from blood vessels and internal organs 11-44 Nerve Fiber Classification Special somatic efferent fibers • carry motor impulses from brain to muscles used in chewing, swallowing, speaking, and forming facial expressions Special visceral afferent fibers • carry sensory impulses to brain from olfactory and taste receptors Special somatic afferent fibers • carry sensory impulses to brain from receptors of sight, hearing, and equilibrium 11-45 Cranial Nerves 11-46 Cranial Nerves I and II Olfactory (I) • sensory • fibers transmit impulses associated with smell Optic (II) • sensory • fibers transmit impulses associated with vision 11-47 Cranial Nerves III and IV Oculomotor (III) • primarily motor • motor impulses to muscles that • raise eyelids • move the eyes • focus lens •adjust light entering eye Trochlear (IV) • primarily motor • motor impulses to muscles that move the eyes 11-48 Cranial Nerve V Trigeminal (V) • mixed • 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 11-49 Cranial Nerves VI and VII Abducens (VI) • primarily motor • motor impulses to muscles that move the eyes Facial (VII) • mixed • sensory from taste receptors • motor to muscles of facial expression, tear glands, and salivary glands 11-50 Cranial Nerves VIII and IX Vestibulocochlear (VIII) • sensory • sensory from equilibrium receptors of ear • sensory from hearing receptors Glossopharyngeal (IX) • mixed • sensory from pharynx, tonsils, tongue, and carotid arteries • motor to salivary glands and muscles of pharynx 11-51 Cranial Nerve X Vagus (X) • mixed • somatic motor to muscles of speech and swallowing • autonomic motor to viscera of thorax and abdomen • sensory from pharynx, larynx, esophagus, and viscera of thorax and abdomen 11-52 Cranial Nerves XI and XII Accessory (XI) • primarily motor • motor to muscles of soft palate, pharynx, larynx, neck, and back Hypoglossal (XII) • primarily motor • motor to muscles of the tongue 11-53 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) 11-54 Spinal Nerves Dorsal root • axons of sensory neurons in the dorsal root ganglion Dorsal root ganglion • cell bodies of sensory neurons Ventral root • axons of motor neurons whose cell bodies are in spinal cord Spinal nerve • union of ventral root and dorsal root 11-55 Dermatome • an area of skin that the sensory nerve fibers of a particular spinal nerve innervate 11-56