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Flashcards in Spinal Cord Deck (32):
1

Conus Medullaris

End tip of the spinal cord

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Level of conus medullaris in newborns and adults

Newborns: L3/L4 Adults: L1/L2

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Areas of the spinal cord that are enlarged

Cervical (5-T1) , Lumbosacral (L1-L3) : limbs need more innervation

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Ventral median fissure

Wide groove on the anterior midline

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Dorsal median sulcus

Narrow groove on the posterior midline

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Order of nerves from medial to lateral

Spinal cord, rootlet, root, spinal nerve, rami

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White matter: 3 tracts

Dorsal, spinothalamic, Lateral corticopinal (pyramid) tracts

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Dorsal column of white matter

  • Primary ascending fibers
  • Transmits ipsilateral fine touch/proprioception
  • Subsets: Fasciculus gracilis/cuneatus
  • Synapses w/ 2º fibers within the nuclei of medulla, then decussates

9

Ascending fibers

Sensory fibers

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Fasciculus gracilis

Subset of dorsal column that carries lower body info

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Fasciculus cuneatus

  • Subset of dorsal column, carries upper body information
  • Only found in the upper body

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Decussation

Crossing over the midline

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Spinothalamic tract

  • in both lateral and ventral columns
  • 2º ascending fibers (synpasing in dorsal gray horn)
  • Lateral tract transmits Contralateral pain/temp
  • Anterior tract transmits crude touch/pressure
  • synapse with 3º in thalamus

14

Clinical: unilateral lesions of spinothalamic tract cause what?

Contralateral anesthesia, 1-2 segments below lesion

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Lateral Corticospinal (pyramidal tract)

  • Lateral column of white matter
  • Formed by descending upper motor neurons
  • Synapse with lower motor neurons in ventral gray horn for distribution to keletal muscle for voluntary motor  control

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Descending neurons

Motor neurons

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Upper motor neurons

  • Originate in the motor cortices of the Cerebrum
  • decussate in medulla at the pyramids
  • Run contralaterally in spinal cord
  • Contralateral motor control

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Lower motor neurons

  • Synapse with UMN in ventral gray horn
  • Connect UMN with muscles for voluntary muscle control

19

Clinical: what happens if there is a lesion in the lateral cortiocospinal tract?

Paralysis below the level of damage

20

Gray matter: neurons and portions

  • Primarily formed by neural cell bodies, axon terminal branches, dendrites
  • Ventral, lateral, dorsal, horns and gray commissure

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Ventral horns of gray matter

  • Found in all levels of the spinal cord
  • Contains Somatic motor neurons

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Somatic

voluntary, skeletal muscle

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Efferent

Going away (exiting) the CNS to motor neurons

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General Somatic efferents

  • aka Lower motor neurons
  • Innervate skeletal muscles

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Dorsal Horns of gray matter

  • Found in all levels of spinal cord
  • contains central processes of sensory neuron axons and interneurons

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General Somatic Afferents

  • aks sensory neuron axons
  • Take sensory info to the brain

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Interneurons

  • aka Ia
  • Integrate various sensory and motor neurons

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Lateral horns of gray matter

  • Found only in spinal cord segments T1 to L2
  • Contains preganglionic sympathetic neuron cell bodies

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General Visceral Efferents

  • Relays information for the preganglionic (autonomic nervous system) sympathetic (excitement neurons) neuron bodies
  • Goes to the involuntary muscles

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Gray Commissure

  • Found at all levels of the spinal cord
  • Connects the left and righ gray columns
  • Area of decussation

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Central Canal

  • Continuous with the 4th ventrical of the brain
  • Contains cerebrospinal fluid
  • May be occluded in aged or diseased spinal cord

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