PNS  Structure of Nerves  Cranial Nerves  Spinal Nerves  Sensory receptors  Motor control

Structure & Classification of Nerves Classification: Sensory, Motor, Mixed, Cranial & Spinal nerves; Ganglia

Cranial Nerves 12 pair of nerves –arise from brain –exit through foramina leading to muscles, glands and sense organs in head & neck Input & output ipsilateral except CN II and IV

I: Olfactory Nerve II: Optic Nerve

III: Oculomotor Nerve & IV: Trochlear Nerve

V: Trigeminal Nerve VI: Abducens Nerve

VII: Facial Nerve VIII: Vestibulocochlear Nerve

IX: Glossopharyngeal Nerve X: Vagus Nerve

XI: Accessory Nerve XII: Hypoglossal Nerve

Cranial Nerve Disorders Trigeminal neuralgia (tic douloureux)Trigeminal neuralgia (tic douloureux) –recurring episodes of intense stabbing pain in trigeminal nerve area –pain triggered by touch, drinking, washing face –treatment may require cutting nerve Bell’s palsyBell’s palsy –disorder of facial nerve causes paralysis of facial muscles on one side –may appear abruptly w/ full recovery w/in 3-5 weeks

Spinal Nerves - 31 pairs of mixed nerves - connect to cord via dorsal & ventral roots and rootlets - away from cord branch into dorsal & ventral rami - nerve plexuses - nerve damage

Dermatomes: skin segment innervated by cutaneous sensory spinal nerve

Sensory Receptors Stimulus typeStimulus type: –mechanoreceptor, thermoreceptors, nociceptors, chemoreceptors & photoreceptors SourceSource: –exteroceptors, interoceptors & proprioceptors Structural complexityStructural complexity : –simple vs. c omplex

Organization of Somatosensory System Receptor level 1. Receptor level: sensory receptors Circuit level 2. Circuit level: ascending fiber tracts Perceptual level 3. Perceptual level: cerebral cortex

Hierarchy of Motor Control