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Neuro Unit 2 > 7 Motor System > Flashcards

7 Motor System Flashcards

1
Q

What type of motor neurons innervate extrafusal muscle fibers?

A

alpha motorneurons

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2
Q

What sensory structures are connected in parallel with extrafusal fibers?

A

muscle spindles

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3
Q

What types of fibers and motor neurons exist in muscle spindles?

A

intrafusal fibers and gamma motorneurons

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4
Q

supraspinal activation causes what?

A

stimulation of alpha motor neurons to contract extrafusal fibers AND GAMMA MOTOR NEURONS TO CONTRACT ASSOCIATED MUSCLE

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5
Q

loss of corticospinal fiber innervation to inhibitory interneurons explains what?

A

exaggerated stretch reflex after UMN lesions

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6
Q

Medial motor groups of the ventral horn innervate?

A

axial muscles

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7
Q

Lateral motor groups in the ventral horn innervate?

A

intrinsic limb muscles originating in trunk

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8
Q

Lateral-most motor neurons in the ventral horn innervate what?

A

distal muscles

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9
Q

Dorsal groups of motor neurons innervate what?

A

flexors

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10
Q

ventral groups of motor neurons innervate what?

A

extensors

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11
Q

Is the spinal reticular core essential for motor function?

A

Yes- central pattern generator

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12
Q

What do spinal interneurons do?

A

generate stereotypic movements

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13
Q

what is the name for neurons contained entirely within the spinal cord

A

propriospinal fibers

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14
Q

What are the 2 main things spinal interneurons effect?

A

specific gaits and upper/lower limb coordination

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15
Q

Pontine and medullary reticular formations contain interneurons which interact with>

A

bulbar motor neurons

  • -centers for stereotypic head and neck movements
  • -saccades
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16
Q

what reticular formations directly involved in saccades?

A

paramedian pontine reticular formation

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17
Q

What are the 3 major types of movements?

A

voluntary, stereotypic and postural control

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18
Q

What movement is willed, purposefully and fractioned?

A

voluntary-limbs, eyes and orofacial (language)

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19
Q

What movement is hard-wired movements of the head and limbs and eyes and tongue involving coordination of several muscle groups?

A

stereotypic

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20
Q

Are stereotypic movements present at birth?

A

yes

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21
Q

What movement is because humans are upright and extensors play the principal role?

A

postural

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22
Q

Postural movements is dominated by what system?

A

vestibular [may control mostly gamma motor neurons to increase muscle tone]

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23
Q

Where does the corticospinal and corticobulbar system originate?

A

cerebral cortex-

[mostly motor cortex, but also premotor, somatosensory cortex an adjacent parietal cortex]

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24
Q

What contains a representation of the opposite side of the body (homunculus)

A

M1 motor cortex

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25
Q

How much of motor cortex is dedicated to hand and the jaw/lowerface?

A

40%

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26
Q

T-F—Corticospinal fibers have its strongest influence on extensor muscle groups?

A

False–flexor muscle groups

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27
Q

About what percentage of cortico spinal fibers synapse on Alpha motor neurons?

A

20%- [particularly in dorsal part of the ventral horn in the cervical enlargement]

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28
Q

Where are motor neurons for intrinsic hand muscles located?

A

dorsal part of the ventral horn C7-T1

29
Q

What is thought to allow individual and fractioned movements of the hand and forearm?

A

direct innervation by corticospinal fibers on intrinsic hand muscle motor neurons

30
Q

If only 20 % of corticobulbar fibers contact motor neurons what do the remainder connect to?

A

pre-motor neurons in the pontine and medullary reticular formation

31
Q

What is thought to mediate voluntary control over posture?

A

anterior corticospinal pathway

32
Q

Where does the rubrospinal pathway originate?

A

red nucleus of the midbrain

33
Q

Does the rubrospinal pathway have a huge significance in humans?

A

no- but in all mammals it facilitates next and upper limb flexors [non-human primates over time the pathway can take over much of the function of the corticospinal tract after a lesion]

34
Q

What is the reticulospinal pathway involved in?

A

maintenance of posture and in the modulation of muscle tone–[other may include visceromotor activity and pain modulation]

35
Q

Where does the medial reticulospinal pathway originate?

A

pontine tegmentum

36
Q

Where does the lateral reticulospinal pathway originate?

A

central and ventral medulla

37
Q

Does the medial or lateral reticulospinal pathway run in the anterior funiculus?

A

Medial—lateral runs with the lateral corticospinal funiculus

38
Q

Where do reticulospinal neurons receive input from?

A

cortico-reticular fibers and fastigial nucleus of the deep cerebellar nuclei

39
Q

Where do most medial reticulospinal fibers end?

A

bilaterally on interneurons in the ventral horn—some alpha motor neurons for axial muscles

40
Q

Do medial or lateral reticulspinal fibers excite or inhibit axial and proximal limb extensors?

A

medial through influence on interneurons and gamma motor neurons
[lateral generally inhibit same groups]

41
Q

T-F–medial reticulospinal neurons are involved in activation compound limb movements and stereotypic limb movements?

A

True- also may be involved in steering head and trunk movements

42
Q

What may be important command systems for complex stereotypic movements?

A

descending monoaminergic pathways from locus ceruleus and pontine/midbrain raphe

43
Q

IS the pontine and midbrain raphe use noradrenaline or serotonin for command systems?

A

serotonin—locus ceruleus uses noradrenaline

44
Q

does the medial reticulospinal system have a component that sends fibers to the phrenic and accessory respiratory motor nuclei?

A

Yes–arise in the medulla and influence by pontine and medullary respiratory centers

45
Q

Where does the tectospinal pathway arise? end?

A

middle and deep layers of superior colliculus—only extends to cervical spinal levels

46
Q

What does the tectospinal pathway innervate? what is it’s effect?

A

contralateral ventral horn—excites motorneurons of contralateral neck and inhibits ipsilateral muscles

47
Q

Where does the lateral vestibulospinal pathway originate? where does it descend?

A

-lateral vestibular nucleus

ipsilateraly through the whole length of the spinal cord

48
Q

Where does the lateral vestibulospinal pathway end on? what are the effects?

A
  • medial part of ventral horn mostly on interneurons

- excitatory to axial muscles and proximal limb extensors

49
Q

Damage to the brain above the pons leads to decerebrate rigidity how?

A

no antagonism to the lateral vestibulospinal tract by corticospinal fibers

50
Q

T-F—damage to the cortex excluding motor cortex can lead to decorticate rigidity?

A

True–lower limbs and back are extended but arms and neck are flexed

51
Q

Where does the medial vestibule spinal tract arise? goes where?

A

medial vestibular nucleus—-> mostly crossed and extends to mid-thoracic level

52
Q

What does the medial vestibule spinal tract facilitate?

A

extensor muscles for head and neck movements leading to an upright level position for the head

53
Q

What is in charge of planning and preparation for movement?

A

Frontal lobe

54
Q

What is the premotor cortex mostly concerned with?

A

planning movements in response to external cues

55
Q

Do lesions affecting premotor areas have less impact on motor function than motor cortex lesions?

A

Yes–patients can reach for something despite damage to that area in the pre-motor cortex

56
Q

Most corticospinal neurons send off side-branches to where?

A

striatum component of the basal ganglia

57
Q

Neurons in the striatum are capable of what?

A

learning and storing complex motor actions

58
Q

Is the output of the basal ganglia inhibitory or excitatory to the ventral anterior thalamic nucleus?

A

inhibitory

59
Q

What does the ventral anterior thalamic nucleus innervate?

A

premotor cortex—and brainstem reticular formations

60
Q

The frontal lobe effects release of what in the basal ganglia?

A

dopamine

61
Q

Lesions of basal ganglia can produce?

A

reduction in movement or uncontrollable movement

62
Q

Almost all cortical areas send axons where?

A

to the pontine nuclei-

63
Q

do corticopontine fibers outnumber corticospinal fibers?

A

yes 7:1

64
Q

What are the largest source of input to the cerebellum?

A

pontine nuclei

65
Q

Through what nuclei does the cerebellum exert its major influence on the motor cortex?

A

deep cerebellar nuclei and ventrolateral thalamic nucleus

66
Q

What tracts provide continuous information about body and limb position?

A

spinocerebellar tracts and vestibular system

67
Q

What provides the motor cortex with continuous feedback about body and limb position?

A

cerebellum

68
Q

What deficit usually involves degradation of fine movements and postural difficulties?

A

cerebellar

Neuro Unit 2 (12 decks)

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