Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Neuro Exam I > Lower Motor Neurons: Poliomyelitis > Flashcards

Lower Motor Neurons: Poliomyelitis Flashcards

1
Q

brifly describe the architecture of the spinal cord

A
  • grey-white orientation opposite of cerebral cortex
    • white matter = outside: axons
    • grey matter = inside: a mix - parikaryons, dendrites, synapses, axons, ect.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

describe a “typical” mutlipolar neuron

A
  • perikaryon (cell body)
  • dendites: input side
  • axon: output side
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

label picture & explain important features

A
  • outside = white matter, divided into R and L halves by:
    • ventral median fissure
      • deeper (aka fissure): makes broader split between halves
    • dorsal median sulcus
  • inside = grey matter surrounding central canal
    • gray matter:
      • dorsal horn: extends to spinal cord surface (d for distance)
      • ventral horn: wider, does NOT extend to spinal cord surface - contain LMNS*
      • lateral horn - contain LMNs*
    • central canal: continuation of the 4th ventricle
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

where are lower motor neurons (LMNS) found?

A
  • ventral horns (gray matter)
  • lateral horns (gray matter)
  • cranial nerves - except I, II & VIII
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

LMNs in the ventral horn

  • are divdided in what groups?
  • will take what path out of the spinal cord?
A
  • path: ventral roolets -> ventral roots -> spinal nerve -> ventral ramus -> muscle
  • can be categorized in two ways based on:
    1. types of muscle fibers innervated:
      • alpha: extrafusal
        • these extrafusal fibers form motor end plates
        • carry excitatory impules only (cholinergic)
        • receive inputs from interneurons (m/c), UMNs, dorsal root ganglion neuron
      • beta: intrafusal & extrafusal (b for both)
      • gamma: intrafusal fibers of spindle apparatus
    2. location of muscle fibers innervated - ie., somatropoic map:
      • distal parts (extremities): lateral ventral horn
      • flexors: dorsal ventral horn
      • extensors: ventral ventral horn
      • proximal parts (trunk): medial ventral horn
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

describe the innervation mediated by alpha motor neurons

A

(alpha motor neurons = LMNs in ventral horn)

  • receive input from either
    • UMNs (brain)
    • interneurons (m/c)
    • dorsal root ganglion neurons (sensory)
  • deliver: excitatory (cholinergic) innervation only
  • innervate: extrafusal fibers that form a motor end plate
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

alpha motor neurons most commonly receive input from….?

A

(LMNs in the ventral horn)

interneurons

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

what is a motor unit?

A

the total muscle fibers innervated by a single alpha motor neuron

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

what is muscle recrtuiement?

A

activating additional motor units

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

the smaller the motor unit the…?

A

more refined the movement

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

damage to LMNs

  • results in what pathology?
  • explain the mechanism
A
  • flaccid paralysis: hypo - reflexia, tonia in a somatotropic map
  • LMNs cannot receive:
    • hypotonia b/c:
      • no input from UMNs (brain), thus nocontraction via conscious thought
      • UMNs & LMNS required
    • hyporeflexia b/c:
      • no contraction following sensory feedback
      • LMNs required
      • what renders the paralysis “flaccid”
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

somatgotropic map in ventral horn

A
  • lateral: distal body parts (appendages)
  • dorsal: flexors
  • ventral: extensors
  • medial: proximal body parts (trunk + proximal appendages)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

what infection can lead to acute flaccid paralyis?

A

= hyporeflexia, hypotonia

polio infection

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

what part of the pathology behind flaccid paralysis renders the paralysis flaccid?

A
  • the disrupted communication sensation from the motor unit and the LMNs
    • stimulation of muscle does not yield reflex
    • = hyporeflexia component of definition
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

summarize the clinical and histological presentation poliomyeltitis

A
  • clinical: acute flaccid paralysis due to LMN destruction
    • hypotonia: muscles appear flacid
    • hyporeflexia: no DTR or Bakinsi reflexes
    • however, SENSATION INFACT
  • histologically:
    • muscle: denervation neurogenic atrophy
      • shrinked fibers
      • filled with adipose tissue
    • spinal cord: neuronophagia
      • microglial nodules (microglial cells surrounding necrotic tissue), d/t microglial cells -> transform into macrophages -> ingest damaged tissue
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

identify & explain

A

decreased neurogenic atrophy: shrinked fibers size + adipose in perimysial muscle

manifestation of poliomyeltiis

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

identify & explain

A

neuronphagia - microglial nodules in spinal cord

manifestation of poliomyelitis

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

identify & explain

A

neuronphagia - microglial nodules in spinal cord

manifestation of poliomyelitis

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

what key relay centers are found in the dorsal horn?

list them & explain their arrangement:

A
  • from most superficial - i.e., from most distal part of horn, to most deep - ie., most proximal part of horn
    • dorsolateral tract
    • substantia gelatinosa
    • nucleus propius
    • dorsal nucleus of clark
20
Q

which dorsal horn center (s) feed into the spinothalamic tract?

A
  • dorsolateral tract
  • substantia gelatinosa
  • nucleus proprius
21
Q

which dorsal horn centers feed into the spinocerebellar pathway?

A

dorsal nucleus (of clarke)

22
Q

which dorsal horn centers serve as synapses?

list the key information transmitted at each synapse.

A
  • substantia gelatinosa: pain + temp + light touch
    • pain = important: can be modulated via this tract*
  • nucleus proprius: mechanical info + temp
  • dorsal nucleus: propriorecption
23
Q

which dorsal horn centers are secondary neurons?

what does this mean?

A
  • this means they are synaptic centers. therefore
    • substantia gelatinosa
    • nucleus proprius
    • dorsal nucleus
24
Q

dorsalolateral tract

  • relative location on dorsal horn
  • carries what sensations?
  • synaptic center - y/n
  • contributes to what pathway?
A
  • recieves information for dorsal root ganglion*
  • location: most superficial / distal relay center - forms “cap over dorsal horn”
  • carries:
    • discrete pain
    • temperature
  • synapse center - NO
  • contributes to - spinothalamic pathway
25
Q

substantial gelatinosa

  • relative location on dorsal horn
  • carries what sensations?
  • synaptic center - y/n
  • contributes to what pathway?
A
  • location: most distal relay (synaptic) center - dorsalateral most distal overall
  • carries:
    • pain (can modulate)
    • temperature
    • light touch
  • synapse center - YES
  • contributes to - spinothalamic pathway
26
Q

nucleus proprius

  • relative location on dorsal horn
  • carries what sensations?
  • synaptic center - y/n
  • contributes to what pathway?
A
  • location: middle relay (synaptic) center
  • carries:
    • mechanical touch
    • temperature
  • synapse center - YES
  • contributes to - spinothalamic pathway
27
Q

dorsal nucleus (of clarke)

  • relative location on dorsal horn
  • carries what sensations?
  • synaptic center - y/n
  • contributes to what pathway?
A
  • location: most proximal relay (synaptic) center
  • carries: proprioreception from golgi tendon organs & spindle apparatus
  • synapse center - YES
  • contributes to - spinothalamic pathway
28
Q

which dorsal center carries mechanical information?

A

nucleus proprius

29
Q

which dorsal center can regulate pain perception?

A

substantia gelatinosa

30
Q

which dorsal center carries propioreception?

A

dorsal nucleus (of clarke)

31
Q

where does the spinothalamic pathway decussate?

A

ventral white commissure

32
Q

what is the commissural region?

into what components is it divided?

A
  • is the region immediately surrounding the central canal:
    1. dorsal grey commissure
    2. ventral grey commissure
    3. white commissure
      • also ventral (only seen on ventral spinal cord)
      • carries fibers from:
        • ventral corticospinal tract
        • spinothalamic tract
33
Q

what is the white commisure and why is it important?

A
  • portion of the commissure region to ventral to ventral grey commissure
  • carries fibers for anterior cortisospinal & spinothalamic pathways
    • site of dessucation for spinothalamic
34
Q

what key features / changes of a spinal cord cross section can help identify the vertebral level of the cut?

A
  • overall: white matter increases inferiorly
  • region specific:
    • ventral horn lateral expansion: d/t high LMNs -> motor tissue
      • C5-T1 (upper limbs)
      • L2-S3 (lower limbs)
    • presence of a lateral horn (aka intermediolateral nuclei)
      • T1- L2
      • S2-S4
    • presence of cuneate nuclei: until T6
    • narrow ventral & dorsal horns: thoracic
35
Q

how does the gray:white matter ratio generally change moving down the spinal cord?

A

increases (more gray, less white going down)

36
Q

in what spinal cord will cross-section show lateral expansion of the ventral horn?

explain.

A

lateral expansion of ventral horn d/t high # of LMNs innervating appendeges (flexors dorsal, extensors, ventral), and will thus be seen in segments responsible for limb innervation.

  • C5-T1 (upper limb)
  • L2-S3 (lower limb)
37
Q

in what spinal cord segments will cross sections show the presence of a lateral horn?

A
  • T1-L2
  • S2-S4
38
Q

in what spinal cord sections will cross sections show narrow ventral & dorsal horns?

A

thoracic - this is b/c the thoracic musculature (intercostals, ect) doesn’t require much motor innervation / give much sensation feedback

39
Q

in what spinal segments will a cross section show the cuneate fasciculis?

A

everything above T6

40
Q

identify corresponding vertebral region & how you know

A

cervical

  • medium gray: white ratio
  • lateral expansion of ventral horn: C5-T1 (upper limbs)
  • presence of cuneate tracts lateral to gracile (up to T6)
41
Q

identify corresponding vertebral region & explain how you know

A
  • low gray: white matter ratio
  • very narrow ventral & dorsal horns (all thoracic)
  • presence of lateral horn: T1-L2, S2-S4
  • presence of cuneate tract lateral to gracile tract: up to T6
42
Q

identify corresponding vertebral and explain how you know

A
  • high gray:white ratio
  • lateral expansion of ventral horn: S2-L3 (lower limb)
  • presence of lateral horn: T1-L2, S2-S4
43
Q

what is recurrent inhibition?

how is recurrent inhibition mediated:

A
  • definition: inhibitory synapses onto an alpha motor neuron (ventral LMN)
    • carried out by an inhibitory neuron - commonly, inhibitory interneurons
44
Q

what are reeshaw cells?

what role do they play?

A

are inhibitory interneurons that mediate recurrent inhibition by syanpses onto alpha motor neurons in the ventral horn

45
Q

what will disruption of rucurrent inhibition lead to?

how can this happen?

A
  • continuous activation of LMNs: rigid paralysis + hyperreflexia
  • can be caused by strychine poisoning - inhibits renshaw cell
46
Q

post-polio syndrome (SSP)

  • definition?
  • cause?
  • presentation?
  • risk factors?
A
  • definition: resurgence of polio sx ~35 after acute paralytic poliomyelitis
  • cause: collateral growth of axons (following injury to PMNs) temporarily recovers innervation to affected motor unit but then excessive reinervation -> stress -> eventual atrophy
  • presentation:
    • fatigue - m/c
    • muscle weakness: affected muscles > not previous affected
    • muscle / joint pain
  • higher risk associations:
    1. young age of initial infection
    2. severe initial infection
    3. greater physical activity in intervening years

Neuro Exam I (15 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions