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SF2- Exam 4 > Voluntary Motor Pathways > Flashcards

Voluntary Motor Pathways Flashcards

1
Q

Which motor pathways are involved in skilled movement?

A

Corticospinal

Corticobulbar

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2
Q

Explain flexibility of strategy.

A

For knee jerk you are stimulating the same ligament every time causing the same contraction of the same muscle. For voluntary movement you can execute the movement using a variety of different limbs or muscles or sequence.

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3
Q

Neurons from cortical areas make _________ (monosynaptic/ disynaptic/ polysynaptic) connections with the alpha and gamma motor neurons.

A

monosynaptic

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4
Q

It is through __________neurons that signals will go to the spinal cord and brainstem motor nuclei

A

upper motor

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5
Q

The LMN are something called the ___________ pathways because no matter where the signal comes from all of that info has to go to LMN and the information has to converge on this final common pathw

A

final common

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6
Q

Damage of the spinal cord & lesion of motor pathways below the origin of the brachial plexus (C5-T1) and above S4 results in __________.

A

paraplegia.

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7
Q

Damage of the spinal cord at the origin of the brachial plexus results in ________.

A

quadreplegia.

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8
Q

Damage of the spinal cord at the origin of the _________ or above results in asphyxiation and death (without medical intervention).

A

phrenic nerve

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9
Q

This area is th emost important in initiating skilled, controlled motor movements

A

Primary motor cortex

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10
Q

What are the two components of the premotor region?

A
  • Premotor cortex
  • Supplementary cortex
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11
Q

The supplementary motor cortex is motor area _______

A

2

*this is apart of Broadman area 6

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12
Q

•When we talk about area 4 and 6 (motor cortex), it lacks layer ______, which is the inner granular layer

A

4

*Or this layer is extremely small

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13
Q

Because the primary cortex is interested in movement and not analyzing sensory information it lacks a well defined inner granular cortex, so it is referred to sometimes as __________.

A

agranular cortex

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14
Q

What areas 4 and 6 do have is a well defined layer______, which has lots of pyramidal cells; these are projection neurons and area 4 in particular has giant pyramidal cells.

A

5

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15
Q

The cell bodies of the corticospinal tract are found in layer __.

A

5

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16
Q

In the primary motor cortex there are very large pyramidal cells called ________cells and they contribute 30,000 of the 1 million axons

A

betz

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17
Q

There are pyramidal cells in layers 5 and 6 of the cortex. However, the pyramidal cells are different in layer 6. In what way(s)?

A
  • They do NOT form the corticospinal tract
  • They have a single apical dendrite that ascends up to the cortical surface and synaptic input from the upper 4 layers make synaptic contact with this apical dendrite and then a single axon descends the spinal cord to terminate on motor neurons and interneurons.
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18
Q

What are the contributions to the corticospinal tract?

A
  • 1/2 from primary motor cortex
  • Most of the other contributions are from the supplementary motor cortex
  • Some contributions are from the parietal cortex and the somatosensory cortex
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19
Q

What is the evidence that the precentral gyrus is the

‘Primary Motor Cortex?’

A

When you shock the precentral gyrus you can produce a single twitch of a single muscle, particularly in the hands; sometimes you will get contractions of other smaller muscles in the hand but often times you can isolate the direct connection between the cortex and muscles of the hand and forearm and other parts of the body. This can’t be done in any other parts of the brain

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20
Q

What are the characteristics of movements induced by electrical stimulation to the motor cortex?

A
  1. an individual (or a few) muscle
  2. the lowest threshold
  3. short latency

*When you measure the amount of electricity it takes to stimulate a muscle, the threshold for stimulating the motor cortex is the lowest

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21
Q

The more synapses in a pathway, the ________ (longer/shorter) the latency is between stimulus and response

A

longer

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22
Q

When they study the motor cortex, they have developed the motor map which is called the _________; specific areas of the motor cortex control specific parts of the body.

A

homunculus

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23
Q

The ________________artery supplies the cortical region supplying the lower limb.

A

anterior cerebral

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24
Q

The ____________artery supplies the region of the hand and face.

A

middle cerebral

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25
Q

Lesion of which artery can cause monoplegia>

A

Anterior cerebral artery

Middle cerebral artery

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26
Q

Is there spike activity in the extensors when the corticospinal tract is stimulated?

A

No.

*Just during flexion. there is also spike activity prior to the contraction when flexing.

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27
Q

What happened when area 6 was stimulated with activity? Do you get movement?

A
  • You stimulate Brodmann’s area 6 you can get movements but it takes more electricity than area 4
  • If you stimulate supplementary motor area, instead of getting discrete movements you get complex movement like opening and closing the hands, usually bilateral, and postural movements

NOTE: If you lesion area 6 you get apraxia and the patient will have difficulty carrying out complex , purposeful movements

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28
Q

What is ideomotor apraxia?

A

If you ask the patient to mimic/pretend they are combing the hair or touch the nose they can’t do it, BUT if the nose itches they can do it or if they need to push the hair back out of the face they can do that without thinking about it

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29
Q

Is the primary motor cortex involved in “rehearsing” activity?

A

No, only the supplementary motor cortex

30
Q

What is the function of the supplementary motor cortex?

A
  • Plans a strategy for movement requiring sequences of muscles contractions or a planned strategy
  • Important in programming motor sequences and in coordinating bilateral movements and postural responses
31
Q

The supplementary motor cortex controls which muscles?

A

a. postural muscles through the corticospinal tract.

b. distal muscles (such as in the hand) through area 4

32
Q

Lateral premotor cortex controls ____________.

A

proximal limb movements that project or orient the arm to targets

33
Q

What is the function of the lateral premotor cortex?

A
  • Plays a role in interjoint coordination
  • Controls proximal limb movements that project or orient the arm to targets

Ex: If you want to paint something in space the first thing you have to do is get the arm in right position; this is largely controlled by the lateral premotor cortex.

34
Q

What are the three complex movements required for voluntary movement? What parts are the cortex are involved in each movement?

A
  1. Identification of target - posterior parietal cortex (5 & 7)
  2. Plan movement – supplementary motor cortex (6)
  3. Execute movement – primary motor cortex (4)
35
Q

When looking at complex movements the areas of the __________are involved in visually guided behavior; it is important in identifying a target that we want to move toward.

A

parietal cortex

36
Q

The plan of the movement will be done mostly by __________ cortex.

A

supplementary motor

37
Q

The execution of the fine movement done by the hands or feet is done by the ___________cortex

A

primary motor

38
Q

The supplementary motor cortex first organizes the ____________adjustments and then makes possible the desired movement.

A

postural

*•Postural adjustments are required to happen in concert with fine movements

39
Q

Corticospinal fibers pass through the _________ limb of the internal capsule.

A

posterior

40
Q

The corticobulbar fibers controlling the motor nuclei of the brainstem are in the _______.

A

genu

41
Q

Usually the _________is not affected by a lesion of the posterior limb of the IC.

A

Face

42
Q

Capsular lesions are commmonly due to obstuctruction or hemorrhage of which arteries?

A

a) deep branches of the middle cerebral
b) anterior choroidal artery
* Most distal part of the ICA

43
Q

Label

A

NOTE: The corticospinal fibers pass through the brainstem after leaving the internal capsule. The fibers go from the cortex to the pons then they cross in the medulla and form the pyramids.

44
Q

On which level of the brainstem are the cerebral peduncles found?

A

Midbrain

45
Q

Which nerve, tract, and central nuclei are affected in medial midbrain syndrome?

A

Nerve

  • Oculomotor

Tract

  • Corticospinal
  • Corticobulbar
  • Corticopontine

Central Nuclei

  • Substantia nigra
  • Red nucleus (cerebellothalamic fibers)
46
Q

Corticospinal fibers separate into fascicles in the _________pons

A

ventral

47
Q

Medial midbrain syndrome is caused by an occlusion of which artery?

A

P1 of PCA

48
Q

Weber’s syndrome

A

Ipsilateral oculomotor palsy + Contralateral hemiparesis/ hemiplegia

49
Q

Claude’s syndrome

A

Unilateral infarction of the red nucleus and cerebral peduncle, affecting several structures in the midbrain leading to:

  • contralateral ataxia
  • contralateral hemiparesis
  • contralateral hemiplegia of lower facial muscles, tongue, and shoulder
  • ipsilateral oculomotor nerve palsy with a drooping eyelid and fixed wide pupil pointed down and out; probable diplopia
50
Q

Benedikt’s syndrome

A
  • Results from occlusion of the posterior cerebral artery or paramedian penetrating branches of the basilar artery
  • Results from damage to tegmentum
51
Q

Differentiate Weber’s syndrome from Benedick’s syndrome

A

Weber

  • Occlusion of P1 of PCA
  • Hemiplegia

Benedick’s

  • Occlusion of paramedian branches of basilar artery
  • Hemiataxia
52
Q

Differentiate Claude’s syndrome from Benedick’s syndrome

A

Claude

  • Occlusion of P1 of PCA
  • more predominant tremor and choreoathetotic movements

Bendick’s

  • Occlusion of the paramedian branches of basilar artery
  • More characteristic of ataxia
53
Q

Artery of Percheron

A

Rare anatomic variation in the brain vascularization in which a single arterial trunk arises from the posterior cerebral artery (PCA) to supply both sides of brain structures; the thalamus and midbrain.

54
Q

What is the clinical significance of the artery of percheron?

A

bizarre disturbance such as sleep from which the patient cannot be awakened

55
Q

Medial medullary syndrome is caused by occlusion of which artery?

A

Anterior spinal artery

Medial branches of vertebral artery

56
Q

Which tracts and nuclei are affected by medial medullary syndrome?

A

Nuclei

  • CN XII

Tracts

  • Corticospinal
  • Medial leminscus
  • MLF
57
Q

90% of pyramidal fibers decussate (cross) at the junction of the _________ and __________.

A

medulla and spinal cord

58
Q

•The pyramids are the fibers crossing to the other side and they will form the lateral corticospinal tract

  • If there is lesion in the middle of the decussation the symptoms will be __________ because the fibers are crossing in both directions
    • If the lesion was in the pyramids the symptoms would be _________.
A

bilateral;contralateral

59
Q

The lateral corticospinal tract innervates_________motor nuclei of the ventral horn

A

lateral

60
Q

The ventral corticospinal tract innervates _________motor nuclei of the ventral horn

A

medial

*Note: some axons of the ventral tract cross at the segmental level; therefore, the projection is bilateral

61
Q

Lateral motor nuclei innervate____________

Medial motor nuclei innervate ___________

A

limb musculature

axial musculature

62
Q

Corticospinal axons synapse on 4 different types of neurons. What are they?

A

Corticospinal axons synapse on:

  1. alpha motor neurons*
  2. gamma motor neurons* (to muscle spindles)
  3. intrasegmental interneurons (that project within the segment)
  4. intersegmental (propriospinal) interneurons (that ascend & descend to other segmental levels)
63
Q

What characteristics in humans allow for better dexterity?

A

Direct connections from the cortex to lower motor neurons.

*You still have indirect pathway through interneurons but to do learned skilled movements you have the direct connections between cortex and lower motor neuron that lower vertebrates don’t have

64
Q

Corticospinal tract has a:

1) ____________ effect on flexor motor neurons
2) _____________ effect on extensor motor neurons

A

facilitatory

inhibitory

65
Q

Explain the relationship between the corticospinal tract and the Babinski reflex.

A

In babies, the Babinski reflex induces extension and fanning of toes. Once the corticospinal tract grows in, the Babinski reflex is inhibited and the same stimulus will produce flexion instead

66
Q

Activity of ___________ Motor Neurons Is Modulated by the Corticospinal Tract

A

Gamma

67
Q

Very shortly after injury to the brain or spinal cord, upper motor signs may be lacking, and, therefore, may even be falsely interpreted as lower motor neuron signs. This transient state is known as ___________.

A

‘cerebral’ or ‘spinal shock’

68
Q

Spasticity is greater in ________ of the arms but __________ of the legs.

A

flexors; extensors

69
Q

Lesions anywhere along the corticospinal tract produce __________ motor neuron signs

A

upper

70
Q

The difference between the corticobulbar and corticospinal is that corticobulbar, for most clinical purposes, is ___________.

A

bilateral

EXCEPTION: Projections to the lower half of the face and the hypoglossal nerve

71
Q

Pseudobulbar palsy

A

pseudobulbar palsy

*Due to bilaterality of the cortibobulbar tract

SF2- Exam 4 (21 decks)

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