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Cranial and Spinal Nerves

Cranial and Spinal Nerves. Cranial Nerves. emerge from the brain emerge through holes in the cranium - cranial foramina 12 pairs of cranial nerves Contains: - sensory fibers (afferent) - motor fibers (efferent) - both sensory and motor fibers. I Olfactory II Optic

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Cranial and Spinal Nerves

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  1. Cranial and Spinal Nerves

  2. Cranial Nerves • emerge from the brain • emerge through holes in the cranium - cranial foramina • 12 pairs of cranial nerves • Contains: - sensory fibers (afferent) - motor fibers (efferent) - both sensory and motor fibers

  3. I Olfactory II Optic III Oculomotor IV Trochlear V Trigeminal VI Abducens VII Facial VIII Vestibulocochlear IX Glossopharyngeal X Vagus XI Accessory XII Hypoglosseal Cranial Nerves (cont.)

  4. I Olfactory • sensory nerve • Function: - smell (olfactory bulbs) anosmia - loss of sense of smell

  5. II Optic • sensory nerve • Function: - vision (retina) anopsia - defective vision

  6. III Oculomotor • mixed nerve (primarily motor) • Functions: - eyeball movement (4 eyeball muscles and 1 eyelid muscle) - lens accommodation - pupil constriction - muscle proprioception

  7. III Oculomotor (cont.) • Injury or lesion may cause: - strabismus - squinting - ptosis - drooping of upper eye lid - diplopia - loss of accommodation for near vision and double vision

  8. IV Trochlear • mixed nerve (primarily motor) • Functions: - eyeball movement (superior oblique muscles) - muscle proprioception

  9. V Trigeminal • mixed nerve • Functions: - sensations ( face, scalp, teeth, lips, eyeballs, nose and throat lining) - general sensations from the tongue - proprioception (face and scalp) - chewing (muscles of mastication)

  10. VI Abducens • mixed nerve (primarily motor) • Functions: - eyeball movement (lateral rectus muscle) - muscle proprioception

  11. VII Facial • mixed nerve • Functions: - taste (anterior 2/3 of tongue) - proprioception (face and scalp) - facial expression (muscles of the face) • Injury: Bell’s palsy - loss of taste, inability to close eyes

  12. VIII Vestibulocochlear • sensory nerve • Functions: - balance (vestibular apparatus of the internal ear) - hearing (cochlea of internal ear)

  13. VIII Vestibulocochlear (cont.) • Injury may cause: - tinnitus - ringing of the ear or deafness - vertigo - feeling of rotation, dizziness - ataxia and nystagmus - involuntary rapid movement of the eyeball

  14. IX Glossopharyngeal • mixed nerve • Functions: - taste (posterior 1/3 of the tongue) - proprioception for swallowing (throat muscles) - blood pressure receptors (carotid sinuses)

  15. X Vagus • mixed nerve • Functions: - chemoreceptors (blood oxygen concentration, aortic bodies) - pain receptors (respiratory and digestive tracts) - sensations (external ear, larynx, and pharynx) - taste (tongue)

  16. X Vagus (cont.) • Functions: - heart rate and stroke volume (pacemaker and ventricular muscles) - peristalsis (smooth muscles of the digestive tract) - airflow (smooth muscles in bronchial tubes) - speech and swallowing (muscles of larynx and pharynx)

  17. XI Accessory • mixed nerve (primarily motor) • Function: - head rotation (trapezius and sternocleidomastoid muscles

  18. XII Hypoglosseal • mixed nerve (primarily motor) • Functions: - speech and swallowing (tongue and throat muscles)

  19. Classification of Spinal Nerves • all emerge from spinal cord • emerge through holes formed by notches on adjoining vertebrae • 31 pairs • all mixed nerves (containing both sensory and motor) • named and numbered according to region and level of spinal cord from which they emerge

  20. Classification of Spinal Nerves (cont.) • 8 pairs of cervical nerves - first cervical pair emerges between atlas (first cervical vertebra) and occipital bone - first 7 emerge above vertebra of the same number - 8th emerges between 7th cervical vertebra and 1st thoracic vertebra

  21. Classification of Spinal Nerves (cont.) • 12 pairs of thoracic nerves • 5 pairs of lumbar nerves • 5 pairs of sacral nerves • 1 pair of coccygeal nerves - all emerge below vertebra of the same number - emerge through intervertebral foramina

  22. Plexuses (plexus = braid) network of adjacent nerves • cervical plexus: C1 - C5 • brachial plexus: C5 - T1 • lumbar plexus: L1 - L4 • sacral plexus: L4 - S4

  23. Brachial Plexus C 4 C 5 C 6 C 7 C 8 T 1

  24. Lumbo-Sacral Plexus

  25. Dermatomes • specific segment of skin which each spinal nerve innervates • knowledge can help physician determine which segment of the spinal cord or which spinal nerve is affected

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