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Neuro Exam 2 > 12. Motor tracts > Flashcards

12. Motor tracts Flashcards

1
Q

where do upper MNs (UMN) synapse

A

cell bodies in cerbal cortex/brainstem –> descend and synapse with lower MN (LMN) or interneurons

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2
Q

where do LMN synapse and what are the types of LMNs

A

-synapse at sk. M

gamma MN = medium, myleinated, to intrafusal fibers in m. spindles

alpha MN: large, meylinated, to extrafusal fibers sk. M

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3
Q

How to the corticospinal tract (CST) direct path project

A

medial CST –> post Ms (10 % of fibers) - stay ipsi

lateral CST –>limb Ms & fractionation = 90% fibers - go contralat @ pyramidal decussation

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4
Q

what is the path of the direct CST (lateral)

A

cell body of UMN in cortex –>

descent thru post. limb of internal capsule –>

continue in CST , pass thru middle cerebral peduncles, then to ant pons and then to pyramids in medulla –>

cross at the pyramids in lower medulla –>

descend in lat column (fibers = lateral CST)–>

synapse w/ LMN in ventral horn

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5
Q

what areas of the brain initiates voluntary movement

A

primary motor cortex (area 4) in precentral gyrus

-right side controls left & vice versa

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6
Q

what does the Medial CST control

A

postural/proximal movements (neck, shoulder & trunk ms)

DONT cross in medulla

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7
Q

what do corticobulbar tracts control

A

come from ventral part of cortical area 4

go into Br.st and influence Ms innervated by CN 5, 7, 9, 10, 11, 12

-control contralateral side

UMN = CBT fibers ; LMN = CNs

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8
Q

what the flow of the corticobulbar tract

A

cortex –> descend thru genu of internal capsule –> pass thru cerebral pedeuncles, ant pons and pyramids –> stop at specific motor nuclei –>

pons: CN 5,7

or medulla: CN 9, 10, 12

or sp. cord: CN 11

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9
Q

how are LMNs represented in the sp. cord

A

= in ant. horn

  • medial = axial Ms
  • lateral = limbs

LMN innervating:

  • extensor M = lie ventral
  • & flexor m = lie dorsal
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10
Q

what do indirect pathways activate

A

antigravity & axial LMNs

–> sitting/standing up right

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11
Q

medial LMNs recieve input from

A

tectospinal tract

medial & lateral vestibulospinal tract (VST)

medial reticulospinal tract

medial CST

–> go to medial LMN –> axial ms

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12
Q

lateral LMNs recieve input from

A

rubrospinal

lateral retibulospinal

lateral CST

–> lateral MN –> limb Ms

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13
Q

what is the path and fxn of the lateral vestibulospinal tract

A

vestibular nuclei to spinal cord = ipsilateral LMNs innervate postural Ms & limb extensors

fxn: faciliate extension agaisnt gravity

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14
Q

what is the path and fxn of the medial vestibulospinal tract

A

vestibular nuclei to spinal cord = to cervical & thoracic levels (neck/shoulder Ms)

fxn: coordinate head movement

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15
Q

what is the path and fxn of the medial reticulospinal tract

A

pontine reticular formation to spinal cord = ipsi LMNs innervating postural Ms & limb extensors

fxn = facilitation of postural reflexes

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16
Q

what is the path and fxn of the rubrospinal tract

A

red nucleus to spinal cord –> innervate upper limb flexors

fxn: help flex limbs

at cervical & thoracic regions

17
Q

what is the path and fxn of the lateral reticulospinal tract

A

medullary reticular formation to spinal tract

fxn: help flexor MN & inhibit extensor MNs (inhibit spinal segmental reflexes)

18
Q

what is the path and fxn of the tectospinal tract

A

superior colliculus to upper spinal cord to neck Ms

fxn= coordinate head w/ eye movement

19
Q

what are signs of LMN lesions

A
  • flaccid paralysis
  • wasting/atrophy
  • hyporeflexia/areflexia (bc denervation)
  • hypotonia
  • denervation hypersensitivity (fasiculations)
20
Q

what are UMN signs

A
  • CST:

loss of distal extremity strength & dexterity (

babinski sign (inverted plantar reflex)

  • indirect path:

pronator drift

hypertonia: spastic

hyperreflexia

clasp-knife phenomenon/spasticity

21
Q

what is UMN syndrome

A

combo of loss of direct CST & loss of regulation from indirect brainstem motor control

22
Q

how can you different btn the two types of hypertonia

A
  1. spastic = UMN lesion - rate dep. resistance; collapsed resistance at end of ROM
  2. rigidity: basal ganglia disease - no rate/force dep; constant thru ROM
23
Q

how can you determine location of a lesion

A

midbrain = CN 3

pons = CN 6 & 7

medulla = CN 10 & 12

24
Q

compare decorticate vs decerebrate posture in UMN lesions

A

decorticate: lesion above level of red nucleus –> thumb tucked under flexed finger in fist, pronated forearm, flexion @ elbow, LE extended w/ foot inverted
decerebrate: lesion _below red nucleu_s ; but above reticulospinal & vestibulospinal nuclei –> UE pronated and extended & LE extended

25
Q

what results form a complete transection of the spinal cord

A

All sensation 1 or 2 levels below lesion

Bladder and bowel control are lost

Spinal shock –> Loss of tendon reflexes

UMN signs at levels below the lesion –> Hyperactive reflexes, clonus; Babinski; Spasticity

LMN signs at the level of the lesion

26
Q

What occurs when you have a hemisection of the spinal cord

A

Pain and temp from contralat side
–> Complete loss of pain sensation occurs 2 to 3 dermatomes below level of lesion (Lissauer’s tract) = ALS tract

Discriminative touch and conscious proprioception on ipsilateral side = PCML tract

LMN signs at level of lesion = Flaccid paralysis (ant horn)

UNM signs on ipsilateral side = Babinski; Hyperreflexia and Clonus; Muscle weakness; Spasticity (CST)

Pattern of loss is called Brown-Sequard’s syndrome

27
Q

what occurs when a pt has syringomyelia

A

Formation of cysts w/i spinal cord in central canal

–> 1st Pain and temp (Anterior commissure) = “cape” pattern

Motor also lost

  • > LMN signs if ventral horns affected
  • > UMN signs if lateral corticospinal tract is affected
  • most often C4-C5
28
Q

what is anterior cord syndrome

A

Compression/damage to anterior spinal cord

b/c sp. cord infarction, intervertebral disc herniation, and radiation myelopathy

-hit LCST, LMN & ALS bilaterally

29
Q

what is central cord syndrome

A

Compression/damage to central sp cord

usually b/c cervical hyperextension

-ex: syringomyelia

30
Q

what is the presentation of central 7 palsy

A

Lesion of the corticobulbar tract w/ CN 7

Lesion rostral to facial motor nucleus results in drooping of muscles at the corner of the mouth

-opposite side

31
Q

what is the presentation of bells palsy

A

Ipsilateral flaccid paralysis of upper and lower face

32
Q

what are symptoms of spastic cerbral palsy

A

Movement dysfxn: Abnormal supraspinal influences, Failure of normal neuronal selection. Consequent aberrant muscle development

Motor disorders: Paresis, Abnormal tonic stretch reflexes (rest & during movement), Reflex irradiation, Lack of postural preparation prior to movement, Abnormal cocontraction of Ms

33
Q

what happens in ALS (amyotrphic lateral sclerosis)

A

Destroys only somatic MNs (UMNs and brainstem and spinal cord LMNs)

Leads to paresis, myoplastic hyperstiffness, hyperreflexia, Babinski’s sign, atrophy, fasciculations and fibrillations.

CN involvement –> difficulty breathing, swallowing and speaking

34
Q

what is polyneuropathy

A

Involvement of sensory, motor and autonomic

Progressing from distal to proximal

Due to dying-back or impaired axonal transport

Demyelization may also contribute

Neuro Exam 2 (23 decks)

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