A&P Exam 3 - ch 12

  1. CNS tissue is enclosed within the vertebral columns:
    from the foramen magnum to L1
  2. Provides two-way communication to and from the brain
    Spinal cord
  3. The spinal cord is protected by...
    • bone
    • meninges
    • CSF
  4. Epidural Space
    • space between the vertebrae and the dural sheath (dura
    • mater) filled with fat and a network of veins
  5. Sub-arachnoid space
    • filled with CSF
    • best place for spinal tap = cauda equina region
  6. Conus medullaris
    terminal portion of the spinal cord
  7. Filum terminale
    fibrous extension of the pia mater; anchors the spinal cord to the coccyx
  8. Denticulate ligaments
    delicate shelves of menigeal tissue; attach the spinal cord to the vertebrae - entire length
  9. Spinal nerves
    31 pairs attach to the cord by paired roots (Compare to cranial nerves)
  10. Cervical and lumbar enlargements
    sites where nerves serving the upper and lower limbs emerge
  11. Cauda equina
    collection of nerve roots at the inferior end of the vertebral canal
  12. Anterior median fissure
    separates anterior funiculi (columns)
  13. Posterior median sulcus
    divides posterior funiculi (columns)
  14. Gray matter consists of:
    • soma
    • unmyelinated processes
    • neuroglia
  15. Gray commissure
    connects masses of gray matter; encloses central canal
  16. Posterior (dorsal) horns
    interneurons for sensory tracts
  17. Anterior (ventral) horns
    interneurons and somatic motor neurons
  18. Lateral horns
    contain sympathetic nerve fibers (ANS)
  19. Gray Matter: Organization
    • Dorsal half – sensory roots and ganglia;
    • Ventral half – motor roots
    • Dorsal and ventral roots fuse laterally to form spinal nerves
    • Four zones are evident within the gray matter – somatic sensory (SS), visceral sensory (VS), visceral motor (VM), and somatic motor (SM)
  20. white matter - fibers run in three directions
    • ascending
    • descending
    • transversely
  21. white matter - Divided into three funiculi (columns)
    • posterior
    • lateral
    • anterior

    • Each funiculus contains several fiber tracks
    • –Fiber tract names reveal theirorigin and destination, eg. Corticospinal, spinothalamic
    • –Fiber tracts are composed of axons with
    • similar functions
  22. White Matter: Ascending pathways
    Pathways decussate (Why is it important to know WHERE different pathways decussate?)

    • Most consist of two or three neurons
    • –First order: sensory receptor to
    • spinal cord or brain stem (soma in ganglion)
    • –Second order: from cord or brain
    • stem to thalamus (soma in dorsal horn or medulla)
    • –Third order: thalamus to somatosensory cortex (soma in thalamus)

    Most exhibit somatotopy (precise spatial relationships)

    Pathways are paired (one on each side of the spinal cord or brain)
  23. Three Ascending Pathways
    • Dorsal column
    • –Skin sensation & proprioception - Discriminative touch, pressure, limb & joint position
    • –Cuneatus = upper limbs & trunk
    • –Gracialis, lower limbs & lower trunk

    • Spinocerebellar tracts
    • –send impulses to the cerebellum and do not contribute to sensory perception - unconscious proprioception

    • Spinothalamic tracts
    • –Pain, temperature, crude touch
  24. Descending (Motor) Pathways
    • Descending tracts deliver efferent impulses from the brain to the spinal cord, and are
    • divided into two groups
    • –Direct pathways equivalent to the pyramidal tracts
    • –Indirect pathways, essentially all others

    • Motor pathways involve two neurons (upper and lower motor neurons)
    • –Upper = brain to spinal cord
    • –Lower = spinal cord to effector muscle
  25. The Direct (Pyramidal) System
    • Direct pathways originate with the pyramidal neurons in the precentral gyrus (upper motor neuron)
    • Impulses are sent through the corticospinal tracts and synapse in the anterior horn
    • Stimulation of anterior horn neurons activates skeletal muscles via lower motor neurons
    • Parts of the direct pathway, called corticobulbar tracts, innervate cranial nerve nuclei
    • The direct pathway regulates fast and fine (skilled) movements
  26. Indirect (Extrapyramidal) System
    • Includes the brain stem, motor (basal) nuclei, and all motor pathways not part of the pyramidal system
    • This system includes the rubrospinal, vestibulospinal, reticulospinal, and tectospinal tracts
  27. Extrapyramidal (Multineuronal) Pathways
    • Reticulospinal tracts – maintain balance
    • Rubrospinal tracts – control flexor muscles (help regulate antagonistic movement, eg gait)
    • Superior colliculi and tectospinal tracts mediate head movements
  28. Paralysis
    loss of motor function
  29. Flaccid paralysis
    severe damage to the ventral root or anterior horn cells

    –Lower motor neurons are damaged and impulses do not reach muscles

    –There is no voluntary or involuntary control of muscles
  30. Spastic paralysis
    only upper motor neurons of the primary motor cortex are damaged

    –Spinal neurons remain intact and muscles are stimulated irregularly

    –There is no voluntary control of muscles
  31. Spinal Cord Trauma: Transection
    Cross sectioning of the spinal cord at any level results in total motor and sensory loss in regions inferior to the cut

    Paraplegia – transection between T1 and L1

    Quadriplegia – transection in the cervical region

    Partial transection? Only cut one side: is it above or below decussation point?
  32. Poliomyelitis
    Destruction of the anterior horn motor neurons by the poliovirus

    Early symptoms – fever, headache, muscle pain and weakness, and loss of somatic reflexes

    Sadly, motor neurons targeted are often involved in respiration.

    Vaccines are available and can prevent infection. Polio is NOT eradicated. If you have not been vaccinated, you are susceptible.
  33. Amyotrophic Lateral Sclerosis (ALS)
    Lou Gehrig’s disease – neuromuscular condition involving destruction of anterior horn motor neurons and fibers of the pyramidal tract

    Symptoms – loss of the ability to speak, swallow, and breathe, as well as walk & use arms/hands

    Death occurs within five years

    Linked to malfunctioning genes for glutamate transporter and/or superoxide dismutase - involved in protection of neuron health.
Card Set
A&P Exam 3 - ch 12
A&P Exam 3