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NS-1 > Motor Tracts > Flashcards

Motor Tracts Flashcards

1
Q

Where do upper motor neurons arise and what do they synapse with?

A

arise and are contained within crebral cortex or brainstem

synapse with LMN or interneurons of the spinal cord

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2
Q

Where are the cell bodies of LMNs?

What do they innervate?

A

in spinal cord or brain stem

synapse w/ skeletal muscle fibers

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3
Q

What are the types of LMNs?

A

gamma motor: medium sized, myelinated –> intrafusal fibers in muscle

alpha motor: large bodies and large myelinated axons –> extrafusal skeletal muscle

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4
Q

What part of the internal capsule does the corticospinal tract pass through?

A

posterior limb

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5
Q

Where do fibers cross in the corticospinal tract?

A

in the pyramids in the lower medulla

90% decussate = lateral corticospinal tract

10% stay ipsi = not clinically significant

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6
Q

Where is volontary motor movement controlled?

A

primary motor cortex (area 4) in precentral gyrus

(R side usually controls left side of body and vice versa)

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7
Q

Where do fibers of the lateral corticospinal tract descend in the spinal cord?

A

lateral column

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8
Q

Where do fibers from the cortex controlling the legs and arms end up in the lateral corticospinal tract?

A

legs –> lateral

arms –> medial

(across from where they are in the cortex)

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9
Q

Where do UMNs from the lateral corticospinal tract synapse?

A

with LMNs in the ventral horn of the spinal cord

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10
Q

hemorrhage of what arteries could cause issues with the corticospinal tract?

A

Lenticulostriate and ant choroidal As –> internal capsule

posterior cerebral A –> crus cerebri of cerebral peduncles

paramedian branches of basilar A –> pyramids of medulla

anterior and posterior spinal As

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11
Q

What does the median corticospinal tract control?

A

postural and proximal movements

don’t cross medulla

only 10% of fibers - isn’t clinically significant

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12
Q

Where do UMNs of the corticobulbar tract arise?

where do they go?

A

ventral part of cortical area 4 –> to brainstem and cranial nerves

axons cross and control muscles on contralateral side

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13
Q

What part of the internal capsule does the corticobulbar tract pass through?

where does it go to get to the brainstem?

A

genu

to cerebral peduncles –> anterior pons –> pyramids

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14
Q

Where do the axons of the corticobulbar tract cross over?

A

pyramidal decussation

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15
Q

Where are the trigeminal nuclei and how do the UMN run to get there?

A

anterior pons

50/50 split to either side

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16
Q

Where are the facial nuclei and how do UMNs run to get there?

A

lower anterior pons

lower face muscles: controlled contralaterally

upper face muscles: controlled ipsilaterally

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17
Q

What CN nuclei are located in the medulla and how do UMNs of the corticobulbar tract run to get there?

A

hypoglossal nucleus (12)

nucleus ambiguus (9,10)

contralateral projections

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18
Q

Where is the spinal accessory nucleus and how do UMNs from the corticobulbar tract run to synapse there?

A

in anterior horn of cervical spine

ipsilateral projections

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19
Q

Where are LMNs located topographically in the spinal cord?

A

all in anterior horn

proximal neurons = medial

distal = lateral

flexors = posterior

extensiors = anterior

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20
Q

Where do indirect pathways synapse?

A

brain stem

basal ganglia

thalamus

reticular formation

cerebellum

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21
Q

What do medial LMNs receive input from? (5)

A

tectospinal tract

medial vestibulospinal

medial reticulospinal

medial corticospinal

lateral vestibulospinal

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22
Q

What do lateral LMNs receive input from?

A

rubrospinal

lateral reticulospinal

lateral corticospinal

23
Q

What artery supplies both horns of the sinal cord?

A

anterior spinal a

24
Q

Where does the lateral vestibulospinal tract run?

A

lateral vestibular nuclei to spinal cord –> ipsilateral LMNs

innervate postural muscles and limb extensors

(help you extend against gravity)

25
Q

Where does the medial vestibulospinal tract run?

A

superior, medial, and lateral vestibular nuclei –> cervical and thoracic levels = neck and shoulder muscles

ipsilateral?

26
Q

Where are vestibular nuclei located?

A

pons

27
Q

Where does the medial/pontine reticulospinal tract run?

A

pontine reticular formation –> SC –> ipsilateral LMNs

to posteral muscles and limb extensors

28
Q

Where does the rubrospinal tract run?

A

red nucleus of midbrain –> SC –> contralateral LMNs

to upper limb flexors

29
Q

Where does the lateral reticulospinal tract run?

A

medullary reticular formation –> spinal cord –> mainly ipsi, some contra

facilitates flexor motor neurons and inhibits extensors

30
Q

Where doew the tectospinal tract run?

A

superior colliculus of midbrain –> upper spinal cord –> ipsi LMNs

to neck muscles –> visual reflexes to turn head to where eyes and ears are

31
Q

What do you see in LMN lesions?

A

flaccid paralysis

wasting or atrophy

hyporeflexia or areflexia

hypotonia

denervation hypersensitivity = fasiculations (neuron is dying)

32
Q

What do you see in UMN lesions?

A

loss of distal extremity strength and dexterity

babinski sign

hypertonia - spasticity and rigidity

hyperreflexia - clonus

spasticity

pronator drift

33
Q

What is rigidity due to?

A

basal ganglia disease

not rate or force dependent

34
Q

What side do LMN lesions cause clinical signs?

A

same side of lesion!

35
Q

Where do you see clinical signs of UMN lesions?

A

if lesion is above lower medulla –> contralateral side

if lesion is in SC –> ipsilateral side

36
Q

What levels do you see clinical signs of spinal cord lesions?

A

UMN signs below level of lesion

LMN signs at level of lesion

37
Q

What is decorticate posture?

A

due to lesion above level of red nucleus

thumb tucked under fingers in fist

pronated forarm

flexed arms

extended legs, foot inversion

38
Q

What is decerebrate posture?

A

due to lesion below red nucleus, but above reticulospinal and vestibulospinal nuclei

arms extended, pronated

lower extremity extended

39
Q

What do you see in complete transection of SC?

A

all sensation lost 1-2 levels below lesion

bladder and bowel control lost

spinal shock

UMN signs below lesion

LMN signs at level of lesion

40
Q

What do you see in hemisection of the spinal cord?

A

pain and temp from contralateral side of body lost

complete loss of pain 2-3 levels below

discriminative touch and proprioception on ipsilateral side

LMN signs at level on ipsi

UMN signs below on ipsi

*Brown-sequard syndrome

41
Q

What do you see in syringomyelia?

A

pain and temp first affected bc of anterior white commissure –> cape pattern

If ventral horns affected –> LMN signs

If CST affected –> UMN signs

42
Q

What syndrome is syringomyelia associated with?

A

Chiari I

43
Q

What things are damaged in Anterior cord syndrome?

A

lateral corticospinal tract –> UMN ipsi, below level

Anterior horn damage –> LMN ipsi, at level

Lateral spinothalamic tract –> contralateral pain and temp lost

44
Q

What things are damaged in central cord syndrome?

A

*usually due to cervical hyperextension

  1. Ant white commissure affected first –> bilateral pain and temp lost
  2. Ant horn affected –> LMN loss at level
  3. lateral corticopsinal tract –> UMN loss at level
45
Q

What things are damaged in medial medullary syndrome?

A

Pyramid

medial leminiscus –> contra prop, vibration sense

CN 12 nucleus –> tongue deviates toward lesion

46
Q

Hemorrhage of what A can cause medial medullary syndrome?

A

anterior spinal a

47
Q

What things are damaged in lateral medullary syndrome?

A

ALS –> contra loss of pain and temp

Spinal trigeminal nucleus and tract –> ipsi loss of pain and temp to face

Nucleus Ambiguus –> 9 and 10 CN loss

Inferior cerebellar peduncle –> ataxia

48
Q

Hemorrhage of what A can cause lateral medullary syndrome?

A

PICA

49
Q

What is central sevel palsy?

A

lesion of the corticobulbar tract involving 7th CN

If superior to facial motor nucleus:

Ms of the upper face are controlled by fibers from both hemispheres –> can still wrinkle forehead

Ms of lower face controlled by contralateral hemisphere –> drooping ms at corner of mouth on contra side

50
Q

What occurs in Weber syndrome?

A

lesion of midbrain

CN III damage –> ipsilateral motor damage (down and out, dilated pupil)

contra UMN sx

Central 7 sx (contra lower face droop)

uvula dev to same side of lesion (10)

tongue dev to opposite side (12)

ipsi SCM and Trap paralysis (11)

51
Q

Occlusion of what arteries can cause Weber syndrome?

A

posterior cerebral A

branches of basilar A

52
Q

What is Amyotrophic Lateral Sclerosis?

A

ALS

destroys only somatic motor neurons = UMNs and spinal cord LMNs

paresis, myoplastic hyperstiffness, difficulty breathing, swallowing, and speaking

53
Q

What is polyneuropathy?

A

damage of nerves: involvement of sensory, motor and autonomic Ns

Progresses distal to proximal = stocking/glove pattern

(diabetic neuropathy)

NS-1 (50 decks)

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