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Human Anatomy

Human Anatomy. Peripheral Nervous System PNS Part I. 2 Components of PNS. 12 pr. of cranial nerves 31 pr. of spinal nerves So….what is a nerve?. Structure of a Nerve. Structure of a Nerve. Connective tissue organized similar to muscle Epineurium – surrounds the entire nerve.

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Human Anatomy

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  1. Human Anatomy Peripheral Nervous System PNS Part I

  2. 2 Components of PNS • 12 pr. of cranial nerves • 31 pr. of spinal nerves So….what is a nerve?

  3. Structure of a Nerve

  4. Structure of a Nerve • Connective tissue organized similar to muscle • Epineurium – surrounds the entire nerve

  5. Structure of a Nerve 2. perineurium– surrounds a fascicle fascicle Fascicle – a bundle of axons perineurium

  6. Structure of a Nerve Fascicle Perineurium

  7. Structure of a Nerve 3. Endoneurium – surrounds each axon

  8. Types of Nerves • Sensory – all axons in all fascicles going from periphery to spinal cord • Motor – all axons in all fascicles going from spinal cord to skeletal muscle (or other organs) • Mixed – axons within the nerve going in different directions BUT not within the same fascicles. • All axons within a single fascicle are going in only one direction

  9. Structure of a Nerve Axons

  10. Cranial Nerves (12)

  11. Cranial Nerves • Found on inferior surface of brain

  12. Cranial Nerves • Some are sensory n. • Periphery (skin or other organs) to brain • Some are motor n. • Brain to periphery (muscle or another organ) • Some are mixed n. • Both directions • All 12 pr. can be used to test various areas of the brain For instance….

  13. The Optic Nerve A patient comes in with a vision problem

  14. Study Hint for the Cranial Nerves • Make a table with 6 columns • The headings for the 6 columns (L to R) should be: • Number • Name • S, M, or B (B = mixed) • Function • Test • Special features

  15. I Olfactory • Sensory • Olfaction • Bulb

  16. I Olfactory

  17. I Olfactory Olfactory bulb Cribriform plate

  18. Location of Olfactory Bulb Cribriform plates

  19. II Optic • Sensory • Vision • Comprised of axons from rods and cones of retina

  20. II Optic

  21. Extrinsic Eye Muscle • Six muscles that attach to eyeball and are responsible for moving (gazing) the eye within the orbit.

  22. Extrinsic Eye Muscles • Names: • Superior rectus • Inferior rectus • Lateral rectus • Medial rectus • Superior oblique • Inferior oblique

  23. III, IV and VI • Cranial n. III, IV and VI innervate the 6 extrinsic eye muscles • All 3 nerves are pure motor nerves • III – oculomotor • IV – trochlear • VI -- abducens

  24. Extrinsic Eye Muscles • Which nerve innervates which muscle(s)? • LR6SO4 • Superior rectus III • Inferior rectus III • Lateral rectus VI • Medial rectus III • Superior oblique IV • Inferior oblique III

  25. V Trigeminal • Three divisions (branches) of V: V1, V2 and V3

  26. V Trigeminal • V1 – ophthalmic branch, purely sensory

  27. V Trigeminal • V2 – maxillary branch, purely sensory

  28. V Trigeminal • V3 – mandibular branch, both motor and sensory – a mixed nerve branch • Therefore, because V3 is a mixed nerve, the trigeminal nerve has to be considered a mixed cranial nerve.

  29. V3 Trigeminal • Motor to muscles of mastication (chewing) sensory

  30. Tic Douloureux • Sudden discharge of V2 and V3 • Causes intense pain to areas innervated by V2 and V3 • Trigeminal neuralgia • 1/25,000 and usually 40 yo and older

  31. VII Facial

  32. VII Facial • Mixed • Motor to facial muscles (5 branches) • Sensory from taste buds – anterior 2/3 of the tongue • Exits through stylomastoid foramen • Bell’s Palsey -- dysfunction of VII because of viral inflammation • Results in facial muscle paralysis on one side • Usually “cures itself” within weeks or a few months

  33. VII Facial

  34. VIII Vestibulocochlear • Semicircular canals – balance abd equilibrium • Cochlea – hearing

  35. VIII Vestibulocochlear • Sensory • Hearing and balance • Cochlea and semicircular canals

  36. IX Glossopharyngeal

  37. IX Glossopharyngeal • Mixed • Motor to: • Swallowing muscles of pharynx • Parotid salivary gland (saliva producing) • Sensory from: • Taste from posterior 1/3 of tongue • Lining of pharynx • Soft palate

  38. X Vagus • Longest cranial n. in human body • Innervates head, neck, thorax and abdomen

  39. X Vagus • Mixed • Motor to: • Pharyngeal and laryngeal muscles • Organs in thorax and abdomen • Lungs and heart • Liver, stomach, intestines

  40. X Vagus

  41. X Vagus • Mixed • Sensory from: • Pharynx • External auditory canal • Organs of thorax and abdomen

  42. X Vagus Vagotomy – to inhibit gastric acid secretion

  43. XI Accessory

  44. XI Accessory • Motor • Motor to: • Sternocleidomastoid • Trapezius • Pharyngeal and laryngeal muscles

  45. XII Hypoglossal • Motor to muscles of the tongue • Tongue points to side of lesion

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