Central Nervous System: The Spinal Cord

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Central Nervous System The Spinal Cord
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Spinal Cord

• It is about 18 inches long.
• Extends from the brain to the 1st or 2nd lumbar
  vertebrae.
• Long cylinder, 31 continuous segments.
• Each segment contains a pair of spinal nerves.
• Relay information from PNS to CNS.
• Cervical Enlargement Swelling in the spinal cord
  that serves the upper appendages.
• Lumbrosacral Enlargement Swelling in the spinal
  cord that serves the lower appendages.

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Connective Tissue Coverings of the Spinal Cord

• Dura Matter outer most covering of the spinal
  cord
• Not attached to the vertebral column, has a
  space(epidural block) filled with connective
  tissue, blood vessel, and adipose tissue.
• Epidural Block injection of anesthesia to the
  epidural space to block pain from spinal nerves
  in that area.
• Archnoid Middle layer, contains collagen
  elastic fibers.
• Pia Matter Inner layer attached to the neural
  tissue, contains a network of blood vessels.

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Structures of the Spinal Cord

• External Structures
• Conus Medularis Location where spinal cord
  tapers(L2).
• Caudia Equina Horses Tail collection of
  nerves that extend beyond the end of the spinal
  cord.

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Structures of the Spinal Cord

• Internal Structures
• Anterior Posterior Medial Sulcus
  Fissures(grooves) that divide the spinal cord
  into right and left halves.
• Central Canal Narrow passageway filled with
  cerebrospinal fluid (center of cord).
• Gray Matter
• Forms H or butterfly shape in the center of the
  cord.
• Contains unmyelinated fibers neuroglia that
  integrate
• Contains motor, sensory, association neurons.

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Structures of the Spinal Cord

• Internal Structures (cont.)
• White Matter
• Surrounds the gray matter.
• Contains mostly myelinated neurons that relay
  information from sensory to motor neurons.
• Contains two tracts that carry information to and
  from the brain.(Ascending Tract, Descending Tract)

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Anatomical Structures of the Spinal Cord
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Function of the Spinal Cord

• Conduction Pathways
• Ascending Tract Carries sensory information to
  the brain.
• Descending Tract Conveys motor commands from the
  brain.

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Function of the Spinal Cord

• Reflex Arc Rapid way of responding to an
  emergency situation, impulse only travels through
  the spinal cord, not to the brain.
• Receptor Sensory receptor end of dendrite that
  senses change.
• Sensory Neuron Carries impulse to spinal cord.
• Association Neuron Connects sensory neruron to
  motor neuron (carries out response) to illicit
  response.

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Function of the Spinal Cord

• Reflex Arc
• Somatic Reflex Effect skeletal muscle
  (withdrawal reflex, patellar reflex).
• Visceral Reflex Effects smooth or cardiac muscle
  (heart rate, breathing, vomiting, sneezing,
  coughing).

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Reflex Arc
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Damage Disease

• Quadriplegia- Damage to the 4th or 5th cervical
  vertebrae that produces paralysis to the upper
  and lower limbs.
• Paraplegia- Damage to the thoracic vertebrae that
  produces paralysis to the lower limbs.
• Meningitis (spinal or cerebral)- Bacterial or
  viral infection of the coverings of the spinal
  cord or brain, affects the blood supply or
  cerebrospinal fluid resulting in the death of
  neurons.