PNS Structure of Nerves Cranial Nerves Spinal Nerves

PNS Ø Ø Ø 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) – recurring episodes of intense stabbing pain in trigeminal nerve area – pain triggered by touch, drinking, washing face – treatment may require cutting nerve • Bell’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 type: type – mechanoreceptor, thermoreceptors, nociceptors, chemoreceptors & photoreceptors • Source: Source – exteroceptors, interoceptors & proprioceptors • Structural complexity: – simple vs. complex

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

Hierarchy of Motor Control