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Neuro Exam 2 > 100. Motor Tracts > Flashcards

100. Motor Tracts Flashcards

1
Q

Our motor tracts are a ___ neuron system.

A

2 neuron system: Upper motor neuron and Lower motor neuron

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2
Q

Where are our UMN located and where do they travel/synapse?

A

Located in: CTX or brainstem Travel in: descending tracts Synapse: LMN or interneurons in the spinal cord

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3
Q

LMN will innervate what?

A

skeletal muscle

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4
Q

Where are our LMN located and where do they travel/synapse?

A

Located: CB is in the spinal cord or the brainstem Synapse: skeletal muscle fibers

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5
Q

We can have two types of LMN; what are they?

A

Gamma LMN and alpha LMN.

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6
Q

What is the difference between a alpha and gamma LMN?

A

Alpha LMN: large cell body, myelinated -> extrafusal skeletal muscles

Gamma LMN: medium sized, myelinated -> intrafusal muscle spindles. (GI)

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7
Q

What are examples of UMN and LMN?

A

UMN: corticospinal tract and corticobulbar tract

LMN: Cranial nerves and peripheral nerves

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8
Q

Our somatic motor path can take two ways to the our muscles, its final destination. What are they?

A

1. Direct path: CTX -> spinal cord -> muscles

2. Indirect path: CTX -> synapse in brainstem, BG, thalamus, r_eticular formation_, cerebellum -> SC -> muscles

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9
Q

Corticospinal tract uses ________ path.

A

Direct; however it will send collaterals to indirect pathways.

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10
Q

The corticospinal tract is a direct pathway with 2 subpathways: medial corticospinal tract and lateral corticospinal tract.

What are these responsible for?

A
  1. Medial corticospinal tract makes up 10% fibers and controls postural muscles.
  2. Lateral cortispinal tract spakes up 90% of fibers and respondsible volitional control of limb muscles – especially fractional control.
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11
Q

CST descends from the CTX via _______.

A

Posterior limb of internal capsule

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12
Q

The corticospinal tract is a direct pathway with ____ subpathways

A

2 subpathways:

  1. lateral corticospinal tract
  2. medial corticospinal tract.
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13
Q

Where do fibers from corticospinal tract come from?

A

60% of cortical spinal fibers comes from:

1. Primary motor CTX

2. Supplementary motor area

3. Premotor CTX

also;

4. Primary somatosensory CTX

5. Parietal association CTX

6. Cingulate gyrus

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14
Q

Somatotropic organization in the:

  • PMC
  • Internal capsule
  • Medulla (pyramids)
  • LMN in the spinal cord
A
  • PMC:
    • CB of UMN for lower extremity are located medially
    • CB of UMN for upper extremity are located middle 1/3 of the precentral gyrus
  • Internal caspsule:
    • Arms are more rostal and legs
    • Most posterolateral (same orientation as ALS)
  • Medulla:
    • Medial pyramids: UE fibers
    • Lateral pyramids: LE fibers
  • SC (ventral horns)
    • Proximal LMN (trunk) are more medial
    • Distal LMN (extremities) are more lateral.
    • Flexors are more posterior
    • Extensors are more anterior.
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15
Q

Describe the corticospinal tract:

A
  1. CB of UMN are located in the primary motor cortex (precentral gyrus)
  2. Fibers merge to create the corticospinal tract
  3. -> corona radiata
  4. -> posterior limb of the internal capsule, where UE fibers are anterior and LE fibers are posterior.
  5. -> Midbrain: Fibers go into the middle 1/3 of cerebral peduncles
  6. -> Anterior pons
  7. -> Anterior surface of the medulla, where they become the pyramids.
  8. At the medullospinal junction (end of medulla/brainstem), 85- 90% corticospinal fibers cross to the contralateral side as the pyramidal decussation -> lateral corticospinal tract, which goes through the lateral column of SC.
    * 10% of corticospinal fibers, which will go to proximal muscles do NOT cross over at the pyramidal decussation in medulla -> medial (anterior) corticospinal tract, located in the anterior column of SC-> cross over at SC.
  9. Axons that go to cervical region (UE) synapse medially in the SC Axons of the lumbar/sacral region (LE) synapse laterally in the SC
  10. Synapse with LMN in the anterior (ventral) horn of the spinal cord.
  11. Go to skeletal muscle

Note: the CST will send collaterals to indirect pathways.

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16
Q

Primary motor cortex (area 4) in precentral gyrus initiates _____ movement

A

voluntary

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17
Q

Right side of PMC usually controls _____ side of body.

Left side of PMC usually controls ___ side of body.

A

Left

Right

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18
Q

According to the homunculus; our muscles are represented ________; meaning?

A

unequally;

meaning that:

high motor units -> need more cortical area. Examples a are vocal cords, tongue, lips, fingers and thumb

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19
Q

What borders the posterior limb of the internal capsule?

A
  • Medially: thalamus
  • Laterally: GB (globus pallidus) and putamen
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20
Q

THINKING AHEAD: what part of the internal capsule is important for the corticobulbar tract?

A

genu of internal capsule

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21
Q

As the corticospinal tract passes through the posterior limb of the internal capsule; is there any topographic organization?

A

Yes; legs are posterior

arms are rostral

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22
Q

As the lateral CST goes down the spinal cord, where is it located?

A

Lateral column

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23
Q

What are the B.S to the cortical spinal tract at the:

  1. SC
  2. Medulla
  3. Pons
  4. Midbrain
  5. Internal capsule
  6. CTX
A
  1. SC: Posterior spinal A (legs) and anterior spinal a (arms)
  2. Medulla: sulcal branches of the anterior spinal a.
  3. Pons: Paramedial branches of the basilar a.
  4. Midbrain: posterior cerebral a
  5. Internal capsule: lenticulostriate a. or anterior choriodal a of the middle cerebral a.
  6. CTX: foot: ACA and arm: MCA.
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24
Q

What is the function of the medial corticospinal tract?

A

Controls postural and proximal movements of the neck, shoulder and trunk muscles (proximal muscles)

Lateral cares more about distal muscles.

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25
Q

The corticonuclear tract influences all of the muscles innervated by the cranial nerves that aren’t eye muscles

Corticobulbar tract (corticonuclear tract) is a _________ tract.

A

Descending

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26
Q

Corticobulbar tract (corticonuclear tract)

Arises from:

Goes to:

Innervates:

A

Corticobulbar tracts:

  • UMN arise from the lateral 3rd of the primary motor cortex (those involved with face)
  • -> brainstem, where UMN will synapse with cranial nerves (LMN) which will then influence the muscles in the face.
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27
Q

What motor nuclei do the UMN of the corticobulbar tract innervate?

A

CN 5, 7, 9, 10, 11, 12

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28
Q

Does the corticobulbar tract innervate eye muscles?

A

no

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29
Q

What is the corticobulbar tract?

A
  1. CB of UMN are located in the primary motor cortex (precentral gyrus): lateral 3rd of the PMC
    * 2. Fibers will follow the corticospinal tract (located
  2. -> corona radiata
  3. -> genu of the internal capsule.
  4. -> Midbrain: Fibers go into the middle 1/3 of cerebral peduncles
  5. -> Anterior pons
  6. -> Anterior surface of the medulla, where they become the pyramids; along the way, this path is sending branches to the CN motor nucleu (5.7.9.10.11.12); this LMN

Many of the fibers innervate the CNs bilaterally. Ex. fibers from the L PMC act as UMN for the L and R trigeminal N.

Exceptions:

  1. UMN for the facial motor nucleus (CN7) that goes to the forehead will branch bilaterally except for the portion of the facial nerve nucleus (CN VII) that supplies the muscles of facial expression for the lower face, which receives contralateral projections
  2. UMN for hypoglossal (CN12) and nucleus ambiguus, will branch bilaterally, but actual muscles are contrateral.
  3. UMN for accessory nucleus (CN11) will branch to the ipsilaterally nucleus.
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30
Q

Where are the motor nuclei of CNs involved in the corticobulbar tract located?

A

Pons: 5, 7

Medulla: 9, 10, 12,

SC: 11

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31
Q

Many of the fibers innervate the CNs bilaterally.

Ex. fibers from the L PMC act as UMN for the L and R trigeminal N.

What are the exceptions?

A

CN5: bilateral

CN7:

Forehead: bilateral

Lower face: contralateral

CN 9: contralateral

CN 10: contralateral

CN 11: ipsilateral

CN 12: contralateral

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32
Q

As we have said: LMN are found in the anterior horn of the SC.

How are LMN in the spinal cord arranged?

A
  • Medial LMN: go to axial/proximal muscles (those of trunk and head)
  • Lateral LMN: go to muscles in extremeties
  • LMN that innervate extensor muscles are located ventrally (anterior)
  • LMN that innervate flexor muscles are located dorsally (postioer
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33
Q

What do indirect motor pathways do?

A

The indirect pathways provide tonic anti-gravity and axial lower motor neurons.: allowing us to walk, stand up and not fall to the floor.

Thus, they are responsible for involuntary and automatic control of muscle.

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34
Q

Indirect pathways originate at the ________

A

brainstem

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35
Q

What are the medial UMN tracts?

Indirect pathways

A

1. Tectospinal tract

2. Medial reticulospinal tract

3. Lateral vestibulospinal tract

4. Medial vestibulospinal tract

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36
Q

What are the lateral UMN tracts, which afftect lateral LMN in the spinal cord?

Indirect pathways

A

1. Rubrospinal tracts

2. Lateral reticulospinal tract.

37
Q

The _________________ tracts do not decussate, providing ipsilateral innervation. The ____________ tracts do decussate, and therefore provide contralateral innervation

A
  • The [vestibulospinal and reticulospinal] tracts do not decussate, providing ipsilateral innervation.
  • The [rubrospinal and tectospinal] tracts do decussate, and therefore provide contralateral innervation
38
Q

Rubrospinal tract arise from _____ in the ______ of the brainstem ->

Ipsilateral/ contralateral

A
  • Red nucleus in the midbrain -> spinal cord to innervate upper limb flexors.
  • Contralateral.
39
Q

Reticulospinal tract arise from _____ in the ______ of the brainstem.

A

Note that there are is an anterior reticulospinal tract and a lateral reticulospinal tract that arise from two different places.

  • Lateral (medullary) reticulospinal tract arises from:
    • [medullary reticular formation -> SC]: facilitate flexor motor neurons and inhibit extensor motor neurons.
    • Ipsilateral
  • Medial (pontine) reticulospinal tract: pontine reticular formation-> innervate postural muscles (reflexesto be alert)
    • ipsilateral
40
Q

Tectospinal tract arise from _____ in the ______ of the brainstem ->

A

Tectospinal tract arise from:

  • Contralateral
41
Q

Vestibulospinal tract arise from vestibular nuclei in the ______ of the brainstem.

A
  • Lateral vestibulospinal tract:
    • [superior vestibular nuclei in the pons-> SC: limb extensors at all levels]
      • ​ipsilateral
  • Medial vestibulospinal tract -> _[_medial and inferior vestibular nuclei in the medulla –> cervical and thoracic levels SC: neck and shoulder muscles]
    • ipsilaterally.
42
Q

Draw the indirect pathways and where they originate at appropriately on a brainstem.

A
43
Q

In general; the medial LMN of the SC get info from:

A

Medial LMN receive iput from?

    1. Tectospinal tract
    1. Medial reticulospinal tract
    1. Lateral vestibulospinal tract
    1. Medial vestibulospinal tract
    1. Medial corticospinal tract
44
Q

In general; the lateral LMN of the SC get info from:

A

1. Rubrospinal

2. Lateral reticulospinal tract

3. Lateral corticospinal tract

45
Q

Vestibulospinal pathways

A
  • 1. Lateral vestibulospinal tract originates at the vestibular nuclei in the medulla
    • -> ipsilateral anterior column of the spinal cord
    • -> synapses on ipsilateral LMN that help with extension against gravity (extensor muscles for posure)
  • 2. Medial vestibulospinal tract originates at the vestibular nuclei in the medulla
    • -> descendings bilaterally in the anterior column of the spinal cord
    • -> synapses on bilateral LMN that innnervate neck and shoulder extensor muscles that help to coordniate head movements.
46
Q

Reticulospinal pathways

A

1. Medial (pontine) reticulospinal tract

  • Pontine reticular formation of the pons
  • -> anterior column of spinal cord
  • -> ipsilatateral LMN that innervate postural muscles and limb extensors whivh will Inhibition of spinal segmental reflexes

2. Lateral (medullar) reticulospinal tract

  • Medullary reticular formation of the pons; axons will stay mainly ipsilateral but some to go bilateral
  • -> lateral column of the spinal cord
  • -> [mostly ipsilateral] LMN that innervate flexor motor neurons and inhibit extensor motor neuons.
  • -
47
Q

Rubrospinal pathway

A
  • UMN originate red nucleus of the midbrain ->
  • cross over to contralateral side of brainstem
  • Enter SC -> lateral column of spinal cord -> innervate contralateral upper limb flexors.
48
Q

If lateral medullary reticulospinal pathway did not work but all others do what would happen?

A

look like a statue: helps flexors; but inhibits flexors

49
Q

Tectospinal pathway

A

Tectospinal pathway:

  1. Begins at the superior colliculus of the midbrain
  2. -> fibers quickly cross to contralateral side
  3. -> enter contralateral anterior column of SC
  4. -> synapse with LMN in the supper spinal cord, which synapse on neck muscles to help coordinate head movement with eye movement
50
Q

UMN lesions and LMN lesions

Where do they occur?

A
  1. UMN neuron: lesions are those in the brain or SC (proximal to anterior horn)
  2. LMN lesion: lesion at anterior horn or nerve that projects to the muscles
51
Q

UMN syndrome is caused by the loss of what?

A

1. Corticospinal tract (direct pathway)

and

2. Indirect brainstem pathway.

52
Q

What are characteristics of a UMN lesion?

A
  • 1. Hypertonic muscle
    • spastic muscle; producing resistance that is depedent on rate and forcet, making a pocket knick movement
    • Rigitdy caused by dz to BG: not rate or force dependent, resistance is constant throughout motion
  • 2. hyperreflexic muscle (clonus)
  • 3. disuse atrophy: loss of distal strength
  • 4. + Babinski: positive Babinski reflex: tickle someones foot; toes curl UP (inverted plantar flex)
53
Q

What are characteristics of a LMN lesion? (5)

A
  • 1. flaccid paralysis: d/t destruction of final pathway
  • 2. hypotonic
  • 3. hyporeflexic
  • 4. denervation hypersensitivity, which causes fasciculations as ACh is building up.
  • 5. – Babinksi.

Negative Babinski reflex: tickle someones foot; toes curl down

54
Q

why do we see flacid paralysis in a LMN lesion?

A

Because we took out final common pathway (LMN)

55
Q

People with UMN lesions often have hypertonicity.

What are the different kinds?

A

Hypertonia means stiff.

  1. Spasticity is stiffness that is dependent on rate and force. At the end ROM, arm will collapse.
  2. Rigidity is d/t dz of the B.G: stiffness is not dependent on rate or force and is costant.
56
Q

To determine lesions, what tests do we run?

A
  • 1. Muscle strength
  • 2. Muscle tone
  • 3. Reflexes
  • 4. Pathological reflexes
57
Q

What are the first two things we should ask ourselves when determining the location of a lesion?

A

1. Sensory or motor?

2. Body or face?

58
Q

What will ALWAYS tell you the xact location of a lesion?

A

1. LMN

2. Cranial Nerve (CN)

59
Q

Lesions to LMN will cause signs _____________ to the lesion.

A

IPSILATERAL: same side

60
Q

How do we determine the location of a lesion if it is in a UMN?

A

UMN:

    1. If lesion is above lower medulla, where corticospinal tract crosses -> contralateral damage.
    1. If lesion occurs to the UMN in the spinal cord -> ipsilateral damage
61
Q

If there is a spinal cord lesion;

UMN signs and LMN signs will be present

A
  • UMN signs : below and down the level of the lesion.
    • For example: Lesion at C6-> UMN signs C7 all the way down.
  • LMN signs:AT that level of the lesion
62
Q

What is the rule of 5?

A
63
Q

What is de_cor_ticate posture?

A

An UMN lesion that occurs _above t_he red nucleus in the midbrain.

Patient will bring arms to CORe (thumb is tucked under fingers in a flexed position and elbow is flexed) and LE is extended and IR.

64
Q

What is decerebrate posture?

A

UMN lesion

[below the red nucleus of the midbrain, but above the reticulospina land vestibulospinal nuclei.

Patient will have an UE is pronated and extended, LE is extended.

65
Q

in decorticate position, what tract is taken out?

A

rubrospinal tract

66
Q
A
67
Q

Lesion: complete transection of the spinal cord.

What happens?

A
  1. Lose all sensation 1 or 2 levels below lesion due to overlap of dermatomes
  2. Bladder and bowel control are lost
  3. Spinal shock -> Loss of tendon reflexes
  4. UMN signs at levels below the lesion: Hyperactive reflexes, clonus, + Babinski • Spasticity
  5. LMN signs at the level of the lesion
68
Q

What is spinal shock?

A

Acute event at the S.C -> spinal shock, which imitates a LMN problem. Thus, you lose deep tendon reflexes below the level of injury

69
Q

Lesion: Hemisection of spinal cord (Brown Sequard pattern)

4:

A
  1. Loss of pain and temp from contralateral side of body, with complete loss occurs 2 to 3 dermatomes below (Lissauer’s tract)
  2. Loss of discriminative touch and proprioception on ipsilateral side at the same level and below
  3. LMN signs at level of lesion and below.
  4. UNM signs on ipsilateral side of lesion below and down.

5. Total sensory loss at the level of the lesion on the ipsilateral side.

This pattern is a called Brown-seqard syndrome.

70
Q

What is Brown-seqard syndrome?

A

Paralysis with a loss of all sensory information.

(?) weakness or paralysis (hemiparaplegia) on one side of the body and a loss of sensation (hemianesthesia) on the opposite side.

71
Q

With Syringomyelia, what modality is affected first?

A

Pain and temperature bilaterally because anterior commisure (transmits pain and temp) is hit first.

72
Q

What other losses can we see Syringomyelia?

A
  • Motor loss:
    • If ventral horn is affected: LMN signs at the level and below
    • If lateral corticospinal as affected: UMN signs
73
Q

• Anterior Cord Syndrome

A
  • Damage to the anterior portion of the spinal cord, however this may also include the lateral portion of the spinal cord and the corticospinal tract: may be d/t anterior spinal A?
  1. Lateral corticospinal tract: UMN signs upsilateral below level of lesion
  2. lateral spinothalamic tract: contralateral pain and temperature 1-2 segments below
  3. LMN: LMN signs and sx on the ipsilateral side
74
Q

• Central Cord Syndrome

A

Compression and damage to central portion of spinal cord d/t cervical hyperextension.

1. Anterior white commisure is hit first -> bilateral pain and temp

2. Anterior horn: LMN sx at the level

75
Q

Medial medullary lesion

What can it be caused by?

A

Damage to:

    1. Pyramid-> contralateral UMN lesion (hemiparesis- weakness)
    1. medial lemniscus- contralteral loss of propioception and vibration
    1. Hypoglassal nucleus -> tongue deviates to the lesion (tongue will always deviate towards affected side)
  • Can be caused by occlusion of anterior spinal A.
76
Q

Lateral medullary lesion

A

PICA or Wallenberg syndrome

  1. Damage to spinal trigeminal-> ipsilateral loss of pain and temp in face
  2. Nucleus ambiguus (CN9/10) -> hoarsness, no gag reflex, uvula deviates to contralateral side
  3. Vestibular nuclei: N/V, nystagmus,
  4. Spinothalamic tract-> colateral loss of pain and temp to UE, LE, trunk (body
77
Q

What are lesions of the corticobulbar tract?

A

1. Central 7 palsy

2. Bells palsy

78
Q

Central 7 palsy is what?

A

a lesion to the corticobulbar tract that involves CN 7 (facial CN)

79
Q

Muscles of the upper face are controlled by what?

A

Muscles of the upper face (forehead) are controlled by equal numbers of fibers from both hemispheres

80
Q

Muscles of the lower face are controlled by _________

A

Muscles of the lower face are controlled by the contralateral hemisphere

81
Q

In central 7 palsy: • Lesion rostral to facial motor nucleus results in ______

A

drooping of muscles at the corner of the mouth on the contralateral side. Forehead is not lost bc other facial motor nucleus is providing input.

82
Q

• Bell’s palsy is what?

A

Ipsilateral flaccid paralysis of upper and lower face

Loss of innervation to one side of the forehead + lower face

83
Q

what is this

A

central 7 palsy

84
Q

what is this

A

bells palsy

85
Q

What is webers syndrome?

A

Damage to:

  1. CST -> contralateral UMN symptoms (hemiparesis)
  2. CBT -> contralateral lower face droop, UMN CN motor weakness -> exaggerated gag reflex, tongue does to contralteral side

3/ CN3 -> dilated pupil: down and out eye.

86
Q

Amyotrophic Lateral Sclerosis (ALS) damages what?

A

Only somatic motor neurons: UMN and LMN in the brainstem and spinal cord.

87
Q

What are symptoms we see with ALS?

A

1. Paresis

2. Myoplastic hyperstiffness

3. Hyperreflexia

4+ babinkski

5. atrophy

6. fascilation and fibrillations

7. CN involvement causes: difficulty breathing, swalling and speaking

88
Q

Polyneuropathy involves what?

A

sensory, motor and autonomic. Damage progreses from distal -> proximal; like a glove.

This is caused by impaired axonal transport and demyelinization.

89
Q

Spinal shock

A

Spinal shock is the temporary reduction of or loss of reflexes following a spinal cord injur

Neuro Exam 2 (12 decks)

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