PNS
Structure of NervesStructure of Nerves Cranial NervesCranial Nerves Spinal Nerves Spinal Nerves Sensory receptorsSensory receptors Motor controlMotor control
Structure & Classification of Structure & Classification of NervesNerves
Classification:Classification:Sensory, Motor, Mixed, Cranial & Spinal nerves; Ganglia
Cranial NervesCranial 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 Spinal NervesNerves
- 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:Dermatomes: skin segment skin segment innervated by cutaneous innervated by cutaneous sensory spinal nervesensory spinal nerve
Sensory ReceptorsSensory Receptors
• Stimulus typeStimulus type:– mechanoreceptor, thermoreceptors, nociceptors,
chemoreceptors & photoreceptors
• SourceSource:– exteroceptors, interoceptors & proprioceptors
• Structural complexityStructural complexity:– simple vs. complex
Organization of Organization of Somatosensory Somatosensory SystemSystem
1. Receptor levelReceptor level: sensory receptors
2. Circuit levelCircuit level: ascending fiber tracts
3. Perceptual levelPerceptual level: cerebral cortex
Hierarchy of Motor ControlHierarchy of Motor Control