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Neuroscience > Lecture 6: Motor and Premotor Cortex > Flashcards

Lecture 6: Motor and Premotor Cortex Flashcards

1
Q

what are the 3 sections of the motor cortex

A

Primary motor cortex (M1)

Premotor cortex

Supplementary motor
area

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2
Q

which area of the motor cortex has somatotopic organization

A

the primary motor cortex (M1)

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3
Q

which areas are enlarged in the primary motor cortex’s somatotopic organization?

A

motor maps for movements are requiring fine motor control are enlarged (fingerers, face, etc)

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4
Q

what kind of movement is the primary motor cortex involved with

A

voluntary movements of contralateral body parts

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5
Q

what about movement does the primary cortex encode

A

force, direction, distance, and speed of movement

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6
Q

what is alien hand syndrome

A

only contralateral primary motor cortex is activated

involuntary uncontrollable movement of the upper extremity

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7
Q

where is the premotor cortex

A

anterior to the M1 (primary motor cortex) in frontal lobe

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8
Q

what is the function of the premotor cortex?

A

Motor planning - select the appropriate movement to perform

  • Mirror neurons for action observation (watching something we want to learn)
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9
Q

how does the premotor cortex influence motor behaviour

A

primarily via connections with M1

less commonly via axons projecting though the pyramidal tracts

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10
Q

what do premotor cortex lesions cause

A

Impaired:
Speed and automaticity of
reaching/grasping

Sequential movements

Gait and posture

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11
Q

what is the function of the Supplementary Motor Area (SMA)

A

Programming complex sequences and coordinating bilateral movements

  • Selects movements based on previous experience
  • Active during motor imagery practice (imagining doing an action)
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12
Q

what does an unilateral lesion of the supplementary motor area cause

A

complete lack of contralateral movement and impaired ipsilateral movement

Antiphase movements can be affected (arms or legs doing different motions like typing or walking)

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13
Q

what are the 3 inputs to the motor cortex to create movement?

A

intention - prefrontal cortex

planning - premotor cortex +SMA

programming and execution - primary motor cortex

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14
Q

LMNs receive instructions from which 3 sources?

A
  • Upper Motor Neurons
    – Descending pathways
  • Local Circuit Neurons/Interneurons
  • Sensory inputs
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15
Q

how are LMNs organized in the anterior horn

A

▪ Medial = proximal muscles

▪ Lateral = distal muscles

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16
Q

what are interneurons / local circuit neurons?

A

the “middle man” that branches locally to innervate other neurons

primarily inhibitory towards unwanted movement

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17
Q

do interneurons / local circuit neurons project contra laterally or ipsilaterally?

A

both

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18
Q

what are the two types of interneurons / local circuit neurons?

A

long distance

short distance

both link to anterior horn in spinal cord

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19
Q

what are long distance interneurons?

A

activate medial aspect of anterior horn

span multiple levels of spinal cord and can cross sides

bilateral control of Proximal muscles for balance and postural control

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20
Q

what are short distance interneurons?

A

Activate lateral aspect of anterior horn

Span few spinal levels and ipsilateral

Distal muscles for fine motor control

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21
Q

what are the 2 kind of tracts of the descending motor pathways

A

Pyramidal tracts

Extrapyramidal tracts

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22
Q

what are the pyramidal tracts responsible for

A

skilled, voluntary movements of the limbs

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23
Q

where do extrapyramidal tracts originate

A

in the brainstem

24
Q

what are the extrapyramidal tracts responsible for

A

posture balance, gait

25
Q

what are the 3 pyramidal pathways

A

lateral corticospinal pathway

anterior corticospinal pathway

corticobubar pathway

26
Q

what are the 4 extrapyramidal pathways

A
  • Vestibulospinal Tract
  • Reticulospinal Tract
  • Tectospinal Tract
  • RubrospinalTract
27
Q

where are the extrapyramidal pathways located?

A

most are in the medial part of spinal cord

28
Q

where does the lateral cortocospinal tract originate?

A

motor cortex, mostly M1

29
Q

where does 85% of the corticospinal tract cross

A

the pyramidal decussation

30
Q

what is the destination of the lateral corticospinal tract

A

lateral LMN of spinal cord or short distance interneurons

31
Q

what would a lesion on the lateral corticospinal tract cause

A

Impairments on contralateral side

32
Q

does the anterior corticospinal tract cross to the other side?

A

not at the medulla, but most of it crosses in the spinal cord

33
Q

what is the destination of the anterior corticospinal tract

A

Terminates bilaterally in spinal cord

  • via long distance interneuron networks
34
Q

what is the function of the anterior corticospinal tract

A

Gross control of proximal postural muscles

35
Q

what happens if there is a lesion on the anterior corticospinal tract

A

there is minimal clinical effect

36
Q

do most corticospinal fibers synapse directly with LMNs

A

some do that are involved with finer muscle control

most synapse with spinal interneurons that in turn synapse with LMNs

37
Q

where does the corticobulbar tract originate?

A

motor cortex

38
Q

what is the function of the corticobulbar tract?

A

Controls efferent activation of cranial nerves

38
Q

what is the destination of the corticobulbar tract

A

Most terminate bilaterally on local circuit neurons in brainstem

LMN nuclei of cranial nerves

39
Q

What region of the face is the primary motor cortex responsible for?

A

lower face (contralateral)

40
Q

what would an UMN injury (in the corticobublar tract) cause

A

Weakness in contralateral inferior facial
muscles

very concerning

41
Q

what would a LMN injury in the facial nerve cause

A

Weakness in ipsilateral superior and
inferior facial muscles

injury is outside of brain so less concerning

42
Q

If there is a lesion to the right facial nerve, where would you expect there to be weakness?

A

inferior and superior right side of face

43
Q

what happens with a transverse cord lesion

A

both sides of the level of spinal cord

Bilateral loss of pain/temperature, vibration/position sense, and voluntary motor function at and below lesion

43
Q

What part of the brain would you expect to have a lesion if you have difficulty tapping your head and rubbing your belly at the same time?

A

Supplementary motor
area

44
Q

what happens with a hemicord lesion (Brown-Sequard Syndrome)

A

damage to one half of spinal cord

Ipsilateral loss of vibration/position sense and voluntary motor function

Ipsilateral loss of pain and temperature over 1-2 segments near lesion

Contralateral loss of pain and temperature

45
Q

what is the destination of the extrapyramidal pathways

A

antero-medial white matter of spinal cord

Innervates bilateral local long interneuron
circuits

46
Q

what is the function of the rubrospinal tract

A

Modulation of flexor muscle tone

47
Q

what is the function of the Vestibulospinal tract

A

posture and balance

48
Q

what is the function of the Reticulospinal tract

A

gait, posture, excites/inhibits muscle tone

49
Q

what is the function of the Tectospinal tract

A

Eye/head motion

50
Q

what are the 4 clinical presentations of extrapyramidal disorders?

A

Slowing or loss of voluntary and automatic movements

Postural instability

Abnormal movements

Usually bilateral deficits

51
Q

which system controls volitional control

A

pyramidal tracts

52
Q

which system controls automatic control

A

extrapyramidal tracts

53
Q

do the pyramidal systems have more long or short local circuit neurons

A

Mostly short distance local circuit neurons (except anterior corticospinal tract)

54
Q

do the extrapyramidal systems have more long or short local circuit neurones

A

Long distance local circuit neurons

55
Q

What is the function of the Lateral Corticospinal Tract

A

Main voluntary motor pathway

  • Skilled, voluntary movements of the limbs

Neuroscience (10 decks)

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