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Peripheral

Peripheral. Nervous System. Ch 13. ____Cranial nerves attach to brain. ___Spinal nerves attach to spinal cord. 12 pair. 31 pair. Nerves. Bundles of axons in the PNS. Sensation: The conscious or subconscious awareness of external or internal stimuli. Perception:

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Peripheral

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  1. Peripheral Nervous System Ch 13

  2. ____Cranial nerves attach to brain ___Spinal nerves attach to spinal cord

  3. 12 pair 31 pair

  4. Nerves Bundles of axons in the PNS

  5. Sensation: • The conscious or subconscious awareness of external or internal stimuli. • Perception: • The conscious awareness and the interpretation of meaning of sensations.

  6. Peripheral sensory receptors By location: • Exteroceptors • Sensitive to stimuli arising from outside body • Interoceptors • Or visceroreceptors, from internal viscera • Proprioceptors • Monitor degree of stretch in skeletal muscles, tendons, joints and ligaments

  7. General Sensesvs. Special Senses • Pain • Temperature • Light touch • Pressure • Sense of body and limb position • Taste • Smell • Vision • Hearing • Balance

  8. Sensory Receptors • Mechanoreceptors • Thermoreceptors • Photoreceptors • Chemoreceptors • Nociceptors • Osmoreceptors

  9. General Senses Unencapsulated Nerve Endings Encapsulated Nerve Endings vs Free nerve endings skin, bones, internal organs, joints Deeper tissue, muscles Encapsulated nerve endings

  10. Unencapsulated Nerve Endings • Free Nerve Endings • Pain & Temperature • Merkel’s Discs • Light Touch & Pressure • Root Hair Plexuses • Light Touch

  11. Encapsulated Nerve Endings Meissner’s Corpuscles Discriminative Touch in Hairless Skin Areas Pacinian Corpuscles Deep Pressure Krause’s End-Bulbs Discriminative Touch in Mucous Membranes Ruffini’s Corpuscles Deep Pressure & Stretch (Proprioception)

  12. The Epidermis Merkel cell Merkel Cells- slow mechanoreceptors (basal layer)

  13. Skin Receptors free nerve endings Merkel disc Meissner’s corpuscles Ruffini corpuscle root hair plexus Pacinian corpuscles

  14. Encapsulated Nerve Endings Proprioceptors Muscle Spindles - Skeletal Muscle Stretching Golgi Tendon Organs - Tendon Stretching Joint kinesthetic receptors – monitors stretch in synovial joints; sends info to cerebellum and spinal reflex arcs • to cerebrum, • cerebellum and • spinal reflex arcs

  15. Muscle Spindle & Tendon Organ

  16. Peripheral motor endings • Innervation of skeletal muscle • Innervation of visceral muscles and glands

  17. Motor axons innervate skeletal muscle fibers at neuromuscular junctions = motor end plates

  18. Motor unit: motor neuron & all the muscle fibers it innervates All muscles in motor unit contract together when neuron fires Stimulation of single motor unit causes weak contraction of entire muscle (spread out)

  19. Innervation of visceral muscles & glands • Near end organ visceral motor axon swells = presynaptic terminals (vesicles with neurotransmitters): action slow (NT diffuses)

  20. Pain- protective function Somatic Pain-results from injuries to skin, muscle, joints, tendon vs.Visceral Pain- pain in body organs

  21. Referred Pain-felt on the body surface

  22. Referred Pain

  23. Nerve Damage & Repair in PNS • Mature neurons are amitotic • If the soma of a damaged nerve is intact, axon will regenerate • Involves coordinated activity among: • Macrophages—remove debris • Schwann cells—form regeneration tube and secrete growth factors • Axons—regenerate damaged part • CNS oligodendrocytes bear growth-inhibiting proteins that prevent CNS fiber regeneration

  24. Endoneurium Schwann cells 1 The axon becomes fragmented at the injury site. Droplets of myelin Fragmented axon Site of nerve damage Figure 13.4 (1 of 4)

  25. Macrophages clean out the dead axon distal to the injury. 2 Schwann cell Macrophage Figure 13.4 (2 of 4)

  26. Axon sprouts, or filaments, grow through a regeneration tube formed by Schwann cells. 3 Aligning Schwann cells form regeneration tube Fine axon sprouts or filaments Figure 13.4 (3 of 4)

  27. The axon regenerates and a new myelin sheath forms. 4 Site of new myelin sheath formation Schwann cell Single enlarging axon filament Figure 13.4 (4 of 4)

  28. Cranial Nerves • On OldOlympus Towering Tops A Fat Voracious German Viewed A Hop • Olfactory- smell • Optic- vision • Oculomotor- 4 of the 6 extrinsic eye muscles • Trochlear- extrinsic eye muscles • Trigeminal- sensory fibers to the face and motor fibers to the chewing muscles • Abducens- controls eye muscles that turn the eye laterally • Facial- facial expression • Vestibulocochlear- hearing and balance • Glosopharyngeal- tongue and pharynx • Vagus- parasympathetic control of heart, lungs & abdominal organs • Accessory- accessory part of vagus nerve, neck & throat muscles • Hypoglossal- moves muscles under tongue

  29. Cranial Nerves

  30. Olfactory Nerves I Olfactory bulb Olfactory tract Filaments of olfactory nerve Olfactory receptor cell

  31. Optic Nerves II

  32. Oculomotor Nerves III

  33. Trochlear Nerves IV

  34. Trigeminal Nerves V

  35. Abducens Nerves VI Lateral rectus muscle cut Abducens nerve

  36. Facial Nerves VII

  37. Vestibulocochlear Nerves VIII

  38. Glosopharyngeal Nerves IX

  39. Vagus Nerves X

  40. Accessory Nerves XI

  41. Hypoglossal Nerves XII

  42. sensory pathway motor pathway Nerve Pathways into the Spinal Cord

  43. Spinal nerves

  44. Spinal nerves • Dorsal roots – sensory fibers arising from cell bodies in dorsal root ganglia • Ventral roots – motor fibers arising from anterior gray column of spinal cord Ventral root ganglia

  45. Dorsal and ventral roots join in an intervertebral foramen forming spinal nerve • Outside foramen, re-branch as rami (sing., ramus):Dorsal and ventral rami (somatic) Rami communicantes (visceral) Spinal nerve

  46. Dorsal rami serve the muscles and skin of the posterior trunk • Back, from neck to sacrum, innervated in a neatly segmented pattern: horizontal strip at same level as emergence from spinal cord • Ventral rami serve the muscles and skin of the lateral and anterior trunk • In thorax only, a simple segmented pattern as intercostal nerves • Also serve the limbs

  47. Dorsal ramus Cross section of thorax showing main roots and branches of a spinal nerve • In the thorax, each ventral ramus continues as an intercostal nerve Ventral ramus Intercostal nerve

  48. Spinal Nerves Nerve plexuses Cervical nerves C1-C8 • Networks of successive ventral rami that exchange fibers (crisscross & redistribute) • Mainly innervate the limbs • Thoracic ventral rami do not form nerve plexuses Thoracic nerves T1-T12 Lumbar nerves L1-L5 Sacral nerves S1-S5 Coccygeal nerve C0

  49. Cervical Plexus • Formed by ventral rami of C1–C4 • Innervates skin and muscles of the neck, ear, back of head, and shoulders • Phrenic nerve • Major motor and sensory nerve of the diaphragm (receives fibers from C3–C5)

  50. Cervical Plexus

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