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Neurology > Spinal Cord 2 > Flashcards

Spinal Cord 2 Flashcards

1
Q

where are the motornuerons found?

A

in the ventral horn

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2
Q

2 kinds of motorneurons

A
  • alpha

- gamma

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3
Q

alpha motorneurons

A
  • go to skeletal muscle
  • somatic efferent fibers
  • go to extrafusal fibers
  • end as motor end plate
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4
Q

gamma motorneurons

A
  • go to intrafusal fibers (muscle spindle)

- send sensory info to tell how contracted the muscle is

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5
Q

distribution of motorneurons

A
  • shoulder muscles: upper cervical region
  • hand muscles: low cervical/upper thoracic

*what’s the point? explains our segmental arrangement

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6
Q

what is a similarity of the motorneurons in the ventral horn to the dosral horn?

A

both are arranged somatitopically

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7
Q

intermediolateral column contains what?

A

visceral motor nuerons

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8
Q

lateral motor column supplies:

A

muscles of the limb

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9
Q

medial motor column supplies:

A

axial muscles

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10
Q

describe the convergence of afferents to a ventral horn motorneuron

A
  • 4 descending tracts come down to converge on the neuron (corticospinal, reticulospinal, vestibulospinal, rubrospinal and tectospinal)
  • an inhibitor and excitatory spinal reflex converges on it
  • the motorneuron axon extends as the final common pathway to a muscle
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11
Q

lower motor neurons =

A

alpha motor neurons - arise from anterior horn cells and project to skeletal muscle

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12
Q

upper motor neurons =

A

arise in the CNS, stay in CNS, and descend to act on lower motor neurons

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13
Q

what would happen if there were a lesion on a lower motor neuron? and why?

A
  • hyporeflexive

- reflex arc is no longer in tact

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14
Q

what would happen if there were a lesion on a upper motor neuron? and why?

A
  • hyperreflexive
  • reflex arc still intact
  • think of McNeils example of the women w/ massive stroke that kicked him in the head
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15
Q

what are the afferent fibers that enter the dorsal root?

A
  • group A fibers

- C fibers

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16
Q

group A fibers

A
  • large and myelinated
  • come into dorsal column w/o synapsing and ascend
  • FAST
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17
Q

what do group A fibers carry?

A
  • proprioception
  • discriminative touch
  • vibration
  • 2 point sensory info
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18
Q

C fibers

A
  • tiny unmyelinated fibers
  • from spinothalamic tract
  • slower
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19
Q

what do C fibers carry?

A

signals related to . . .

  • pain
  • temp
  • poorly localized touch
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20
Q

how is the group A fibers / C fibers interaction significant in real life?

A
  • when you hurt yourself, there is a second where you know what happened but it doesn’t hurt, you just know the pain is coming
  • the “something touched me” sense is faster than the pain sense
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21
Q

where does sensory start?

A

at the sensory endings for primary afferents in the DRG

  • there are specialized receptors for everything
  • examples: pacinian corpuscle, ruffini endings, meissner corpuscle, etc.
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22
Q

fasciculus proprius

A
  • interconnects segments of SC - helps w/ reflexes
  • has axons that don’t leave SC
  • sends info up and down more segments
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23
Q

Why is a spinal cord injury not a precise cut off?

A
  • the fasciculus proprius

- the fact that dermatomes also overlap

24
Q

What are the clinically important long tract systems (note: this is repetitive)

A 
SENSORY
-spinothalamic 
-dorsal column aka medial lemniscal 
-spinocerebellar 
MOTOR
-corticospinal
25
Q

spinothalamic tract

A

-transmits pain, temp and poor localization into the CNS and up to thalamus

26
Q

dorsal column aka medial lemniscal system

A

-transmits discriminative touch, proprioception, vibration, 2 pt discrimination to consciousness into the CNS and up to thalamus

27
Q

spinocerebellar projections

A

-relay info about muscle tension, limb position and spinal cord level of activity to cerebellum for planning of movements

28
Q

corticospinal projections

A

-most important of the upper motorneurons in the control of fine movement

29
Q

where are primary afferent (first order) sensory neurons?

A

in the DRG

30
Q

where do primary afferent axons synapse?

A

on the same side as the DRG cell body (ipsilateral)

31
Q

what do secondary afferent neurons (second order) receive?

A

primary afferent synapses form ipsilateral DRG cells

32
Q

secondary afferent neurons project where?

A

to the contralateral ventral thalamus to synapse on 3rd order neurons

33
Q

tertiary afferent (3rd order) neurons project where?

A

from thalamus to cerebral cortex

34
Q

spinothalamic tract

  • enters where?
  • synapses where?
A

enters and synapses in lamina 2 then crosses (decussates in cord)

35
Q

dorsal column aka medial lemniscal pathway (group A fibers)

  • enter?
  • synapse?
  • go where?
A
  • enter and ascend on same side
  • synpase w/ 2nd order neuron in MEDULLA
  • cross there and got to VPL then cortex
36
Q

what must happen for us to be aware of these pathways?

A

they MUST reach the cortex

37
Q

if you see a pathway crossing in the white commissure, what does it tell you?

A

it’s spinothalamic tract

38
Q

once the pathways reach the VPL of thalamus, where specifically do they go?

A

post central gyrus

39
Q

post central gyrus is aka

A

primary somatosensory area

40
Q

distribution of the sensory homunculus

A
  • more nervous system in the post central gyrus is dedicated to face and index finger than anything else
  • indicates importance
41
Q

what is the origin of the corticospinal tract?

A

motor cortex aka pre central gyrus

42
Q

motor homunculus

A

-closely resembles the sensory homunculus

43
Q

blood supply of motor homunculus that supplies the face and upper extremity?

A

middle cerebral a.

44
Q

blood supply of motor homunculus that supplies the leg?

A

anterior cerebral a.

45
Q

corticospinal projections

  • what it provides
  • what happens when lost
  • where decussation occurs
A
  • cortex provides volitional control over intended movements
  • w/o it, one loses fine fractionated control
  • pyramidal decussation occurs at the spinomedullary junction
46
Q

describe the pathway of the corticospinal projections

A

precentral gyrus –> bottom of medulla to decussate –> descend down lateral corticospinal tract –> synapse on motor nuerons –> muscle

47
Q

spinal injury above the medulla would effect what? give example

A
  • upper motor neurons

- ex: stroke

48
Q

spinal injury below the medulla would effect what? give example

A
  • lower motor neurons

- ex: SC injury

49
Q

UMN lesion

A
  • disuse atrophy
  • fasciculations (quivering)
  • spastic paralysis
  • hyperreflexia
50
Q

LMN lesion

A
  • atrophy
  • flaccid
  • flaccid paralysis
  • hyporeflexia
51
Q

syringomyelia

A
  • damage around the central canal

- pressure on crossing fibers causes a loss of pain and temp to those segments on both sides

52
Q

tabes dorsalis

A
  • damage to dorsal column
  • almost always secondary to tertiary syphilis
  • lose touch and proprioception
  • when they walk they can’t feel their feet touch the ground
53
Q

in a drug deal gone bad when the bullet hits the lateral faniculus, what does it affect?

A

corticospinal and spinothalamic tracts but NOT dorsal column

54
Q

brown-sequard syndrome

A
  • hemisection of SC

- causes 4 neural deficits

55
Q

what are the 4 neural deficits caused by brown-sequard syndrome?

A
  1. loss of pain and temp at opposite side and below
  2. loss of light tough and 2pt ipsilateral and below
  3. upper motor lesion ipsilateral below level of lesion
  4. lower motor lesion at level of lesion d/t injury of cells directly, not axons

Neurology (11 decks)

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