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The Spinal Cord and Spinal Nerves

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Radial Nerve Injury Caused by improper intramuscular injections into the deltoid or when the cast is applied too tightly around the mid-humerus. – PowerPoint PPT presentation

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Title: The Spinal Cord and Spinal Nerves


1
The Spinal Cord and Spinal Nerves
  • Dr. Michael P. Gillespie

2
Protective Structures
  • Bony vertebrae
  • Meninges
  • Cerebrospinal fluid (produced in the brain)

3
Vertebral Column
  • The spinal cord is located within the vertebral
    canal of the vertebral column.
  • The vertebral foramina form the canal.
  • The vertebrae form a shelter for the cord.
  • The vertebral ligaments, meninges and CSF also
    provide protection.

4
Functions of the Spinal Cord and Spinal Nerves
  • White matter contains the sensory and motor
    tracts (highways).
  • Gray matter site for integration (summing) of
    action potentials.
  • Spinal nerves connect the CNS to sensory
    receptors, muscles, and glands.

5
Meninges
  • Connective tissue coverings that encircle the
    spinal cord and brain.
  • Spinal meninges.
  • Cranial meninges.

6
Meninges
  • 3 spinal meninges.
  • Dura mater (most superficial).
  • Epidural space between dura mater and wall of
    vertebral canal.
  • Arachnoid mater (middle layer) spider web
    arrangement.
  • Subdural space between dura and arachnoid.
  • Pia mater (innermost layer).
  • Subarachnoid space between arachnoid and pia
    contains CSF.
  • Denticulate ligaments extend from pia and fuse
    with arachnoid.

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8
External Anatomy of the Spinal Cord
  • Cervical enlargement nerves to and from the
    upper limbs
  • Lumbar enlargement nerves to and from the lower
    limbs

9
External Anatomy of the Spinal Cord
  • Conus medullaris the spinal cord tapers to a
    conical portion
  • Filum terminale an extension of the pia mater
    that anchors the spinal cord to the coccyx

10
External Anatomy of the Spinal Cord
  • Cauda equina horses tail
  • Spinal nerves paths of communication between
    the cord and the nerves innervating specific
    regions of the body
  • Posterior (dorsal) root
  • Sensory nerve axons
  • Posterior (dorsal) root ganglion swelling
    cell bodies
  • Anterior (ventral) root
  • Motor nerve axons

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12
Spinal Tap
  • Spinal tap (lumbar puncture).
  • Local anesthetic is given and a long needle is
    inserted into the subarachnoid space.
  • Uses.
  • Withdraw CSF for diagnosis.
  • Introduce antiobiotics, contrast media,
    anesthetics.
  • Introduce chemotherapy.
  • Measure CSF pressure.

13
Internal Anatomy of the Spinal Cord
  • Anterior median fissure.
  • Posterior median sulcus.

14
Internal Anatomy of the Spinal Cord
  • Gray commissure form the crossbar of the H.
  • Anterior (ventral) gray horns cell bodies of
    somatic motor neurons and motor nuclei.
  • Posterior (dorsal) gray horns - cell bodies of
    somatic and autonomic sensory nuclei.
  • Lateral gray horns cell bodies of autonomic
    motor neurons that regulate smooth muscle,
    cardiac muscle and glands.
  • Central canal in the center of the gray
    commissure.

15
Internal Anatomy of the Spinal Cord
  • White columns.
  • Sensory (ascending) tracts.
  • Motor (descending) tracts.

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17
Spinal Cord Physiology
  • 2 principle functions.
  • Nerve impulse propagation white matter tracts.
  • Sensory impulses flow toward the brain.
  • Motor impulses flow from the brain.
  • Information integration gray matter.

18
Sensory Motor Tracts
  • The name of the tract often indicates its
    position in the white matter and where it begins
    and ends.

19
Sensory Tracts
  • Lateral and anterior spinothalamic tracts.
  • Convey impulses for pain, warmth, tickling,
    itching, deep pressure, and a crude sense of
    touch (poorly localized).
  • Posterior columns.
  • Convey impulses for proprioception,
    discriminative touch, 2 point discrimination,
    light pressure sensations, and vibrations.

20
Motor Tracts
  • Direct pathways convey precise voluntary
    movements.
  • Lateral corticospinal.
  • Anterior corticospinal.
  • Corticobulbar.

21
Motor Tracts
  • Indirect pathways govern automatic movements
    (I.E. Reflexes).
  • Rubrospinal.
  • Tectospinal.
  • Vestibulospinal.

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23
Reflexes and Reflex Arcs
  • Reflex a fast, unplanned sequence of actions
    that occurs in response to a particular stimulus.
  • Location of integration.
  • Spinal reflex.
  • Cranial reflex integration in brain stem.
  • Types of reflexes.
  • Somatic reflexes contraction of skeletal
    muscles.
  • Autonomic (visceral) reflexes responses of
    smooth muscle, cardiac muscle, and glands.

24
Reflex Arc
  • Reflex arc (reflex circuit) - the pathway
    followed by nerve impulses.

25
Five Functional Components of a Reflex Arc
  • Sensory receptor.
  • Distal end of a sensory neuron.
  • Responds to a stimulus.
  • Sensory neuron.
  • Nerves terminate in the brain stem or spinal cord.

26
Five Functional Components of a Reflex Arc
  • Integrating center.
  • Monosynaptic reflex arc - A synapse between a
    sensory neuron and a motor neuron.
  • Polysynaptic reflex arc one or more
    interneurons and a motor neuron.

27
Five Functional Components of a Reflex Arc
  • Motor neuron.
  • Effector.
  • The part of the body that responds to the motor
    nerve impulse.
  • Somatic reflex the effector is a skeletal
    muscle.
  • Autonomic reflex the effector is smooth muscle,
    cardiac muscle or a gland.

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29
Reflexes
  • Reflexes are normally predictable.
  • They can provide information about the health of
    the nervous system.

30
Reflexes
  • Damage or disease anywhere along the reflex arc
    can cause the reflex to be absent or abnormal.
  • Somatic reflexes can be tested by tapping or
    stroking the body surface.
  • Autonomic reflexes cannot be tested easily
    because the visceral receptors are deep inside
    the body.

31
Four Important Somatic Spinal Reflexes
  • Stretch reflex
  • Tendon reflex
  • Flexor (withdrawal) reflex
  • Crossed (extensor) reflex

32
Stretch Reflex
  • A stretch reflex causes contraction of a skeletal
    muscle in response to stretching of the muscle.
  • Monosynaptic reflex arc.
  • Ipsilateral reflex.
  • This reflex helps avert injury by preventing
    overstretching of a muscle.
  • Reciprocal inhibition when the stretched muscle
    contracts, the antagonistic muscle(s) relax.

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34
Tendon Reflex
  • The tendon reflex controls muscle tension by
    causing muscle relaxation before muscle forces
    become so great that they tear tendons.
  • Ipsilateral reflex.
  • Sensory receptors tendon (Golgi tendon) organs.

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36
Flexor (Withdrawal Reflex)
  • Causes withdrawal from a painful stimulus.
  • This reflex causes contraction of the flexor
    muscles with causes withdrawal from a painful
    stimulus.
  • Ipsilateral reflex.
  • Several motor units at different levels of the
    spinal cord are recruited intersegmental reflex
    arc.
  • Reciprocal innervation occurs.

37
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38
Crossed Extensor Reflex
  • Helps you maintain balance.
  • Contralateral reflex arc.
  • Reciprocal innervation occurs.

39
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40
Plantar Flexion Reflex
  • The plantar flexion reflex is elicited by
    stroking the lateral outer margin of the sole.
  • The normal response is curling under of the toes.
  • Babinski sign the great toe extends this
    indicates damage to the descending motor
    pathways.
  • The babinski sign is normal in children under 18
    months due to incomplete myelination of the
    axons.

41
Spinal Nerves
  • The spinal nerve has two connections to the cord
    a posterior root and an anterior root.
  • The posterior and anterior roots unite to form a
    spinal nerve at the intervertebral foramen.
  • The posterior root contains sensory axons and the
    anterior root contains motor axons Therefore,
    the spinal nerve is a mixed nerve.

42
Connective Tissue Coverings of Spinal Nerves
  • Endoneurium surrounds individual axons.
  • Perineurium - surrounds bundles of axons called
    fascicles.
  • Epineurium surrounds the entire nerve.

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44
Branches
  • After passing through the IVF, the spinal nerve
    forms rami (branches).
  • Posterior (dorsal) ramus.
  • Anterior (ventral) ramus.
  • Meningeal branch.
  • Rami communicantes serves the autonomic nervous
    system.

45
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46
Plexuses
  • A network of axons.
  • Principle plexuses
  • Cervical plexus.
  • Brachial plexus.
  • Lumbar plexus.
  • Sacral plexus.
  • Coccygeal plexus.
  • The nerves have branches named for the structures
    they innervate.

47
Cervical Plexus
  • The cervical plexus supplies the skin and muscles
    of the head, neck, and superior part of the
    shoulders and chest.
  • The phrenic nerves arise from the cervical plexus
    and innervates the diaphragm.
  • C3, 4 5 keep the diaphragm alive.

48
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49
Brachial Plexus
  • The brachial plexus provides the entire nerve
    supply of the shoulders and upper limbs.

50
Brachial Plexus
  • Major nerves
  • Axillary nerve supplies deltoid and teres minor
    mm.
  • Musculocutaneous nerve supplies arm flexors.
  • Radial nerve supplies posterior arm and forearm
    mm.
  • Median nerve supplies anterior forearm mm and
    some hand mm.
  • Ulnar nerve supplies anteromedial mm of the
    forearm and most of the hand muscles.

51
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53
Erb-Duchenne Palsy
  • Known as waiters tip position.
  • Results from forceful pulling away of the head
    from the shoulder.

54
Radial Nerve Injury
  • Caused by improper intramuscular injections into
    the deltoid or when the cast is applied too
    tightly around the mid-humerus.
  • Indicated by wrist drop.

55
Median Nerve Injury
  • Numbness, tingling, and pain in the palm and
    fingers.
  • Inability to pronate the forearm.
  • Weak wrist flexion.

56
Ulnar Nerve Injury
  • Inability to abduct or adduct the fingers.
  • Atrophy of the interosseous mm of the hand.
  • Clawhand.
  • Loss of sensation over the little finger.

57
Ulnar Nerve Palsy
58
Long Thoracic Nerve Injury
  • Paralysis of the serratus anterior mm.
  • The scapula protrudes.
  • Winged scapula.

59
Long Thoracic Nerve Injury
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61
Lumbar Plexus
  • The lumbar plexus supplies the anterolateral
    abdominal wall, external genitals, and part of
    the lower limbs.

62
Lumbar Plexus Injuries
  • Femoral nerve injury.
  • Can be caused by a stab or gunshot wounds.
  • Inability to extend the leg and lost sensation.
  • Obturator nerve injury.
  • Complication of childbirth.
  • Paralysis of the adductor muscles of the leg and
    loss of sensation.

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65
Sacral and Coccygeal Plexuses
  • The sacral plexus supplies the buttocks, perineum
    and lower limbs.
  • The sciatic nerve originates here.
  • The coccygeal plexus supplies a small patch of
    skin in the coccygeal region.

66
Sciatic Nerve Injury
  • Injury to the sciatic nerve causes sciatica
    pain the extends from the buttock, down the
    posterolateral aspect of the leg and to the foot.
  • Damage to the fibular nerve can cause
  • Footdrop.
  • Equinovarus inverted foot.
  • Calcaneovalgus injury of the tibial portion of
    the sciatic nerve resulting in dorsiflexion.

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68
Dermatomes
  • Specific segments of skin that are innervated by
    specific spinal segments or specific cranial
    nerves.
  • The nerve supply in adjacent segments overlaps
    somewhat.
  • Knowing which spinal segments supply each
    dermatome allows us to determine the location of
    nerve damage.

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70
Terminolgy
  • Meningitis inflammation of the meninges.
  • Nerve block loss of sensation in a region due
    to injection of a local anesthetic.
  • Neuralgia pain along the course of a sensory
    nerve.
  • Neuritis inflammation of the nerves.
  • Paresthesia abnormal sensation.
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