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Neuroscience > Motor Tracts > Flashcards

Motor Tracts Flashcards

1
Q

Where are UMN contained?

A

Cerebral cortex or brain stem

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2
Q

What do UMN synapse with?

A

Synapse with LMN and/or interneurons of

the spinal cord

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3
Q

Examples of UMNs?

A

Corticospinal tract and corticobulbar

(corticonuclear) tract

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4
Q

What do LMN innervate?

A

Skeletal muscle

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5
Q

Where are LMN contained?

A

Cell body in the spinal cord or brain stem

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6
Q

What do LMN synapse with?

A

Synapse with skeletal muscle fibers

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7
Q

Types of LMN?

A
  • Gamma motor neuron

- Alpha motor neuron

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8
Q

medium sized, myelinated, project to intrafusal fibers in muscle spindle

A

Gamma motor neuron

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9
Q

large myelinated axons, project to extrafusal skeletal muscle
large cell bodies and

A

Alpha motor neuron

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10
Q

Examples of LMN

A

Peripheral nerves and cranial nerves

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11
Q

Somatic Motor Pathway:

  • From cerebral cortex to spinal cord and out to muscles
A

Direct Pathways

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12
Q

Somatic Motor Pathway:

  • Includes synapses in brain stem, basal ganglia, thalamus, reticular formation, and cerebellum
A

Indirect Pathways

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13
Q

Is CST direct or indirect?

A

Direct

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14
Q

Type of CST?

• Postural muscles
- 10% of fibers

A

Medial corticospinal tract

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15
Q

Type of CST?

• Limb muscles
• Fractionation
- 90% of fibers

A

Lateral corticospinal tract

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16
Q

Send collaterals to indirect pathways

A

CST

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17
Q

Lateral CST Pathway (Direct):

• Cell bodies arise in cortex

• Descends from cortex through the ?
- Continues in the corticospinal tract passing through: ?

  • Descends in the ? of the spinal cord
  • Synapse with LMNs in the ? of the spinal cord
A
  • posterior limb of the internal capsule
  • Cerebral peduncles middle 1/3 (midbrain)
  • Anterior pons
  • Pyramids (medulla)
  • Fibers cross in the pyramids in the lower medulla
  • lateral column
  • ventral horn
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18
Q

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

  • Right side motor strip usually controls ? side of body and conversely.
  • Area concerned primarily with performance of muscle movements
A
  • voluntary

- left

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19
Q

Homulucus with the most number of motor units

A

vocal cords, tongue, lips, fingers and thumb

  • Lower limb = medial
  • Hand = middle 2/3
  • Face = lateral
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20
Q

• Controls postural and proximal movements
- Neck, shoulder and trunk
muscles

A

Medial Corticospinal Tract

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21
Q

• Pathway is the same as Lateral Corticospinal Tract except ?

  • 10% of fibers
  • Not clinically significant
A

These fibers don’t cross in the medulla

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22
Q

Arises from ventral part of

cortical area 4

A

Corticobulbar (Corticonuclear)

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23
Q 
Corticobulbar:
• Descends into ?
and influences muscles
innervated by cranial
nerves including motor
nuclei: ?

• Axons will cross and control muscles on the ? side

A
  • brain stem
  • V (trigeminal)
  • VII (facial)
  • IX (glossopharyngeal)
  • X (vagus)
  • XI (spinal accessory)
  • XII (hypoglossal)
  • contralateral
24
Q

Corticobulbar Tract:

• When descending will travel through the ?

• Continues in the corticobulbar tract
passing through the ?,?, and the ?

• Will stop at its specific motor nucleus

A
  • genu of the internal capsule

- cerebral peduncles, the anterior pons, and the pyramids

25
Q

• LMN topographically organized

  • Found in ?
  • Medial LMNs project to ? muscles
  • Lateral LMNs project to ? muscles
  • LMNs innervating extensor muscles tend to lie ?
  • LMNs innervating flexor muscles tend to lie ?
A
  • anterior (ventral) horn
  • axial
  • limb
  • ventral
  • dorsal
26
Q

Tonically activate antigravity and axial LMNs

A

Indirect pathways

27
Q

Indirect Pathways:

Medial UMN tracts

A
  • Tectospinal
  • Medial reticulospinal
  • Lateral vestibulospinal
  • Medial vestibulospinal
28
Q

Indirect Pathways:

Lateral UMN tracts

A
  • Rubrospinal

* Lateral reticulospinal

29
Q

Medial LMNs receive input from which tracts?

A
  • Tectospinal tract
  • Medial vestibulospinal tract
  • Medial reticulospinal tract
  • Medial corticospinal tract
  • Lateral vestibulospinal tract
30
Q

Lateral LMNs receive input from which tracts?

A
  • Rubrospinal
  • Lateral reticulospinal
  • Lateral corticospinal tract
31
Q

• In pons

• Vestibular nuclei to
spinal cord

• Ipsilateral LMNs
innervating postural
muscles and limb
extensors

A

Lateral vestibulospinal

32
Q

• In medulla

• Vestibular nuclei to spinal
cord

• To cervical and thoracic
levels (neck and shoulder
muscles)

A

Medial vestibulospinal

33
Q

•. In the pons

• Pontine reticular
formation to spinal cord

• Ipsilateral LMNs
innervating postural
muscles and limb
extensors

A

Medial (Pontine) reticulospina

34
Q

• Medullary reticular formation
to spinal cord

• Facilitates flexor motor
neurons and inhibits extensor
motor neurons

•Mainly ipsilateral with a little bilateral

A

Lateral (Medullary)

reticulospinal

35
Q

• In midbrain

• Red nucleus to
spinal cord

• Crosses to contralateral side

• Innervates upper
limb flexors

A

Rubrospinal

36
Q

• In midbrain

• Superior colliculus to
upper spinal cord
• To neck muscles
- Does visual reflexes (due to superior colliculus)
- Goes auditory (due to inferior colliculus)

A

Tectospinal

37
Q

Which lesion?

• Flaccid paralysis
• Wasting or atrophy
• Hyporeflexia or areflexia due to denervation
• Hypotonia- decreased muscle tone
• Denervation hypersensitivity
- Fasciculations
A

Lower motor neuron lesion

38
Q

a combination of the loss of the corticospinal tract (direct pathway) and the loss of
regulation from the indirect brainstem motor control
pathways

A

UMN syndrome

39
Q

Upper Motor Neuron Signs

A
  • Loss of distal extremity strength and dexterity
  • Babinski sign (inverted plantar reflex)
• Hypertonia
1.  Spasticity: UNM lesion
- Rate dependent resistance 
- Collapse of the resistance at the end of the range of motion
2. Rigidity: Basal ganglia disease
- Not rate or force dependent 
- Constant throughout the range of motion
~ Lead pipe or plastic-like
  • Hyperreflexia: may be seen as clonus
  • Clasp-knife phenomenon and spasticity
40
Q

Lesion Location

  • LMNs result in clinical signs on the ? side as the lesion
A

same

41
Q

Lesion Location:

UMNs
• Above lower medulla (where corticospinal tract crosses) clinical signs will be ?

• In spinal cord clinical signs will be ?

A
  • contralateral

- ipsilateral

42
Q

Lesion Location:

Spinal Cord
• Give UMN signs ? level of the lesion
• Give LMN signs at ?

A
  • below

- the level of the lesion

43
Q

Rule of 5s;

C5 – 
C6 – 
C7 –
C8 – 
T1 – 
L2 - 
L3 - 
L4- 
L5 - 
S1-
A 
C5 – Shoulder  extension
C6 – Arm flexion
C7 – Arm extension
C8 – Wrist extensors
T1 – Hand grasp
L2 - Hip Flexion
L3 - Knee extension
L4- Knee flexion
L5 - Ankle dorsiflexion 
S1- Ankle plantar flexion
44
Q

UMN Lesion:

• Lesion above the level of the red
nucleus

• Thumb tucked under flexed fingers in fisted position, pronation
of forearm, flexion at elbow with the lower extremity in extension
with foot inversion

A

Decorticate posture

45
Q

UMN Lesion:

• Lesion below red nucleus, but above reticulospinal and vestibulospinal nuclei

• Upper extremity in pronation and
extension and the lower extremity in extension

A

Decerebrate posture

46
Q

Hemisection of spinal cord:

• Pain and temp from ? side of body
- Complete loss of pain sensation occurs 2
to 3 dermatomes below level of lesion (Lissauer’s tract)

• Discriminative touch and conscious proprioception on ? side

• LMN signs at ?
- Flaccid paralysis

• UNM signs on ? side of lesion

  • Babinski
  • Hyperreflexia and Clonus
  • Muscle weakness
  • Spasticity

• Pattern of loss is called ?syndrome

A
  • contralateral
  • ipsilateral
  • level of lesion
  • ipsilateral
  • Brown-Sequard’s
47
Q

Formation of cysts within the spinal cord

A

Syringomyelia

48
Q

Syringomyelia:

• Pain and temp first affected

  • Anterior white commissure
  • Resulting pattern is ?

• Motor also lost
- May have LMN signs if
? affected
- May have UMN signs if ? is affected

A
  • shawl or cape
  • ventral horns
  • lateral corticospinal tract
49
Q

• Compression or damage to anterior part of spinal cord

  • Usually due to SPINAL CORD INFARCTION, INTERVERTEBRAL DISC HERNIATION, AND RADIATION MYELOPATHY
A

Anterior Cord Syndrome

50
Q
  • Compression and damage to central portion of spinal cord.

* Mechanism of injury is usually CERVICAL HYPEREXTENSION

A

Central Cord Syndrome

51
Q

• Lesion of the CORTICOBULBAR tract involving the 7th CN

• Muscles of the upper face are controlled by equal numbers of fibers
from both hemispheres

• Muscles of the lower face are controlled by the CONTRALATERAL
hemisphere

• Lesion rostral to facial motor nucleus results in drooping of muscles
at the corner of the mouth
- On the side OPPOSITE the lesion

A

Central Seven Palsy

52
Q

Lesion of Corticobulbar Tract:

IPSILATERAL flaccid paralysis of upper and lower face

A

Bell’s palsy

53
Q

Who can wrinkle their forehead, Bells Palsy or Central 7?

A

Central 7

54
Q
  • Destroys only somatic motor neurons
  • UMNs and brainstem and spinal cord LMNs.

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

• Cranial nerve involvement leads to difficulty breathing,
swallowing and speaking

A

Amyotrophic Lateral Sclerosis (ALS)

55
Q

• Involvement of sensory,
motor and autonomic

• Progressing from distal
to proximal:

  • Due to dying-back or
    impaired axonal transport
  • Demyelization may also
    contribute
A

Polyneuropathy

Neuroscience (14 decks)

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