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Spinal Cord and Spinal Nerves

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Spinal Cord and Spinal Nerves Spinal Cord Enclosed in the vertebral canal, extends from the foramen magnum of the skull to the first or second lumbar vertebra where ... – PowerPoint PPT presentation

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Title: Spinal Cord and Spinal Nerves


1
Spinal Cord and Spinal Nerves

2
Spinal Cord
  • Enclosed in the vertebral canal, extends from the
    foramen magnum of the skull to the first or
    second lumbar vertebra where it terminates in the
    cone shaped conus medullaris

3
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4
Spinal Cord
  • Spinal meninges
  • Dura Mater outer
  • Arachnoid Mater middle
  • Pia Mater inner

5
Spinal Cord
  • Dura Mater composed of dense, irregular
    connective tissue

6
Spinal Cord
  • Arachnoid Mater It is an avascular covering
    with a spiders web arrangement of delicate
    collagen fibers and some elastic fibers

7
Spinal Cord
  • Pia Mater A vascular and thin transparent
    connective tissue layer composed of interlacing
    bundles of collagen fibers and some fine elastic
    fibers

8
Spinal Cord
  • Subarachnoid space between the arachnoid mater
    and pia mater which contains cerebrospinal fluid

9
Spinal Cord
  • The dura mater and arachnoid meningeal coverings
    extend beyond the conus medullaris, approximately
    to the level of S2

10
Spinal Cord
  • Filium terminale a fibrous extension of the pia
    mater, extends farther and attaches to the
    posterior coccyx

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12
Spinal Cord
  • 31 pairs of spinal nerves, which exit via the
    intervertebral foramina

13
Spinal Cord
  • Since the spinal cord doesnt extend to the end
    of the vertebral column, the spinal nerves
    emerging from the inferior end must travel
    through the vertebral canal until reaching the
    appropriate intervertebral foramina

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15
Spinal Cord
  • This collection of spinal nerves are called the
    cauda equina

16
Spinal Cord / Gray Matter
  • Looks like an H

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18
Spinal Cord / Gray Matter
  • Posterior or dorsal horns posterior projections

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20
Spinal Cord / Gray Matter
  • Anterior or ventral horns anterior projections
    that contain cell bodies of motor neurons

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22
Spinal Cord / Gray Matter
  • Lateral Horns In the thoracic and lumbar
    regions there is a lateral outpocketing of gray
    matter

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24
Spinal Cord / Gray Matter
  • Gray commissure central area of gray matter

25
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26
Spinal Cord / Gray Matter
  • Dorsal root Sensory fibers enter the cord here

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28
Spinal Cord / Gray Matter
  • Dorsal Root Ganglia Cell bodies of sensory
    neurons located here

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30
Spinal Cord / Gray Matter
  • Ventral Roots Motor neurons leave the cord here

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32
Spinal Cord / Gray Matter
  • Spinal nerves are formed from the fusion of the
    dorsal and ventral roots

33
Spinal Cord / Gray Matter
  • Spinal Nerves
  • 8 pairs of cervical nerves
  • 12 pairs of thoracic nerves
  • 5 pairs of lumbar nerves
  • 5 pairs of sacral nerves
  • 1 pair of coccygeal nerves

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35
Spinal Cord / White Matter
  • The anterior median fissure and the posterior
    median sulcus divide the spinal cord into R. and
    L. sides

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Spinal Cord / White Matter
  • White matter is divided into columns
  • Posterior Funiculus, Anterior Funiculus, and
    Lateral Funiculus

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39
Spinal Cord / White Matter
  • Each column contains distinct bundles of nerve
    axons called tracts

40
Spinal Cord / White Matter
  • Two Types of Tracts
  • 1. Sensory (ascending) tracts conduct nerve
    impulses toward the brain

41
Spinal Cord / White Matter
  • 2. Motor (descending) tracts conduct impulses
    down the cord

42
Connective Tissue Coverings of Spinal Nerves
  • A fiber is a single axon within an endoneurium

43
Connective Tissue Coverings of Spinal Nerves
  • A fascicle is a bundle of fibers within a
    perineurium

44
Connective Tissue Coverings of Spinal Nerves
  • A nerve is a bundle of fascicles within an
    epineurium

45
Spinal Nerves and Nerve Plexus
  • Each nerve divides into dorsal and ventral rami

46
Spinal Nerves and Nerve Plexus
  • Rami contains both motor and sensory rami

47
Spinal Nerves and Nerve Plexus
  • Dorsal rami serve the skin and musculture of
    the posterior body trunk at their approximate
    level of emergence

48
Spinal Nerves and Nerve Plexus
  • Ventral rami of spinal nerves T2 T12 pass
    anteriorly to supply the muscles of intercostal
    spaces, and the skin and muscles of the anterior
    and lateral trunk

49
Spinal Nerves and Nerve Plexus
  • Ventral rami of all other nerves form complex
    networks of nerves called plexuses

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51
Spinal Nerves and Nerve Plexus
  • The plexuses diverge again to form peripheral
    nerves

52
Spinal Nerves and Nerve Plexus
  • Four Plexuses
  • Cervical
  • Brachial
  • Lumbar
  • Sacral

53
Spinal Nerves and Nerve Plexus
  • Cervical Plexus
  • Supplies the skin and muscles of the head, neck,
    and upper part of the shoulders and diaphragm

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55
Spinal Nerves and Nerve Plexus
  • Damage to the spinal cord above the origin of the
    phrenic nerves causes respiratory arrest.

56
Spinal Nerves and Nerve Plexus
  • Breathing stops because the phrenic nerves stops
    sending impulses to the diaphragm

57
Spinal Nerves and Nerve Plexus
  • Brachial Plexus
  • Supplies the upper extremities and a number of
    neck and shoulder muscles

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59
Spinal Nerves and Nerve Plexus
  • In carpal tunnel syndrome there is damage to the
    median nerve

60
Spinal Nerves and Nerve Plexus
  • Lumbar Plexus
  • Supplies the anterolateral abdominal wall,
    external genitals, and part of the lower
    extremities

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62
Spinal Nerves and Nerve Plexus
  • Femoral Nerve - Largest nerve arising from the
    lumbar plexus

63
Spinal Nerves and Nerve Plexus
  • 4. Sacral Plexus
  • Supplies the buttocks and part of the lower
    extremities

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65
Spinal Nerves and Nerve Plexus
  • Sciatic Nerve Largest nerve arising form the
    sacral plexus

66
Spinal Nerves and Nerve Plexus
  • Sciatica Pain that extends from the buttock
    down the back of the leg due to injury to the
    sciatic nerve

67
Spinal Cord Physiology
  • The white matter tracts are highways for nerve
    impulse conduction to and from the brain

68
Spinal Cord Physiology
  • The gray matter receives and integrates incoming
    and outgoing information

69
Spinal Cord Physiology / Sensory Tracts
  • Sensory information from receptors travels up the
    spinal cord via the
  • Spinothalamic tracts
  • Posterior column tract

70
Spinal Cord Physiology / Sensory Tracts
  • Spinothalamic tracts carry pain, touch, and
    temperature impulses

71
Spinal Cord Physiology / Sensory Tracts
  • Posterior columns carry proprioception and
    vibration

72
Spinal Cord Physiology / Motor Tracts
  • Motor info. travels from the brain down the
    spinal cord to muscles and glands via the
  • Pyramidal tracts
  • Extrapyramidal tracts

73
Spinal Cord Physiology / Motor Tracts
  • Pyramidal tracts control voluntary, purposeful
    motor movement of eyes, mouth, face, arms, and
    legs

74
Spinal Cord Physiology / Motor Tracts
  • Extrapyramidal tracts control more complex
    things like the accessory adjustments we make to
    muscle tone to adjust our posture

75
Spinal Cord Physiology / Reflexes
  • The gray matter of the spinal cord serves as an
    integrating center for spinal reflexes

76
Spinal Cord Physiology / Reflexes
  • A reflex is a fast, predictable, automatic
    response to changes in the environment that helps
    to maintain homeostasis

77
Spinal Cord Physiology / Reflex Arc
  • Five functional components
  • Receptor
  • Sensory Neuron
  • Motor Neuron
  • Integrating Center Neuron
  • Effector

78
Stretch Reflex
  • 1. Slight stretching of a muscle stimulates
    sensory receptors in the muscle called muscle
    spindles

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80
Stretch Reflex
  • 2. In response to being stretched the muscle
    spindle generates a nerve impulse along a somatic
    sensory neuron and enters the spinal cord via the
    posterior root

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82
Stretch Reflex
  • 3. In the integrating center of the spinal cord
    the sensory neuron makes an excitatory synapse
    with a motor neuron in the anterior gray horn

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84
Stretch Reflex
  • 4. If the excitation is strong enough a nerve
    impulse is propagated along the motor neuron
    which extends from the spinal cord to the muscle

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86
Stretch Reflex
  • 5. ACh is released at the NMJ which triggers a
    muscle action potential in the stretched muscle
    (effector) and the muscle contracts

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