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Neuroscience > Exam 3 Motor system > Flashcards

Exam 3 Motor system Flashcards

1
Q

Where are the neuronal cell bodies of the descending pathways?

A

Cortex and brainstem

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2
Q

Where do the descending pathways synapse?

A

On alpha and gamma motor neurons of the ventral horn of the spinal cord and cranial nerve motor nuclei

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3
Q

What are upper motor neurons?

A

The descending pathways and the somas they arise from

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4
Q

What are lower motor neurons?

A

The alpha and gamma motor neurons (whose axons innervate muscle)

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5
Q

What is the largest and clinically most important spinal tract?

A

Corticospinal tract

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6
Q

What is another name for the corticospinal tract?

A

pyramidal tract

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7
Q

Where do most of the somas of the corticospinal tract arise?

A

Primary motor cortex (primarily from the body regions of the homunculus)

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8
Q

What major regions of the brain do the corticospinal tracts pass through on their way to the medulla?

A

Corona radiata, internal capsule, cerebral peduncle

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9
Q

Where do the axons of the descending pathways become tightly packed?

A

Internal capsule

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10
Q

Where do 85-90% of corticospinal tract axon fibers cross (decussate)?

A

In the pyramids of the medulla

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11
Q

What do the crossed corticospinal axons continue as on their way down the spine?

A

Lateral corticospinal tract

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12
Q

What percentage of the lateral corticospinal tract have monosynaptic input to motor neurons?

A

3-5%

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13
Q

What do the 10-15% of uncrossed corticospinal axons continue as on their way down the spine?

A

Anterior corticospinal tract in the anterior funiculus

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14
Q

Which descending pathway is most concerned with voluntary, discrete, skilled movements?

A

Lateral corticospinal tract

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15
Q

Where does the anterior corticospinal tract project to mainly?

A

Cervical and upper thoracic spinal cord

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16
Q

What does the anterior corticospinal tract control?

A

Bilateral axial musculature

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17
Q

Where do corticobulbar tract somas arise?

A

From the face region of the motor cortex

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18
Q

Where do corticobulbar tract axons project to?

A

To the motor nuclei of cranial nerves in the brainstem: CN III, IV, V, VI, VII, IX, X, XI, XII (all but I, II, and VIII)

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19
Q

Most of the corticobulbar tract projections are crossed except one, which is bilateral. Which one is bilateral?

A

The projections to the facial nucleus are bilateral

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20
Q

What is the function of the rubrospinal tract?

A

Control of dextrous movement of the contralateral upper extremity

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21
Q

Where are the cell bodies of the rubrospinal tract?

A

red nucleus of the midbrain

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22
Q

Where do all rubrospinal tract axons cross to the opposite side?

A

In the ventral tegmentum of the midbrain as they exit the red nucleus.

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23
Q

What do rubrospinal tract axons pass thru in the spinal cord?

A

They pass thru the lateral funiculus just anterior to the lateral corticospinal tract (they share this funiculus)

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24
Q

Where do rubrospinal tract axons terminate?

A

At all spinal levels but mostly in the cervical region

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25
Q

Where does the red nucleus receive input from?

A

The cerebral cortex and cerebellum

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26
Q

Which two tracts are alternate routes for achieving voluntary movements?

A

The rubrospinal and reticulospintal tracts

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27
Q

What are the two reticulospinal tracts?

A

Pontine (medial) and Medullary (lateral) reticulospinal tracts

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28
Q

What does the medullary reticulospinal tract pass thru in the spinal cord?

A

Anterior funiculus to all spinal levels

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29
Q

T/F The medullary reticulospinal tract descends both crossed and uncrossed down the spine.

A

True

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30
Q

What type of neurons does medullary reticulospinal tract act on mostly?

A

Primarily on gamma motor neurons, but also on alpha

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31
Q

What is the general function of the medullary reticulospinal tract thought to be?

A

Inhibit lower extremity extensors and facilitate flexors, reducing muscle tone in the lower extremities

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32
Q

The pontine reticulospinal tract descends mostly ________ in the anterior funiculus of the spinal cord to all spinal levels.

A

Uncrossed

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33
Q

While the medullary reticulospinal tract descend both _______ and ________, the pontine reticulospinal tract descends mostly uncrossed.

A

crossed and uncrossed

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34
Q

What is the function of the pontine reticulorspinal tract?

A

It facilitates lower extremity extensor motor neurons, increasing muscle tone

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35
Q

The medullary reticulospinal tract ________ (inhibits/facilitates) lower extermity extensors (LE), while the pontine reticulospinal tract _______ (inhibits/facilitates) the LE extensors

A

Inhibits; facilitates

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36
Q

What are the two vestibulospinal tracts?

A

Lateral vestibulospinal tract (LVST) and medial vestibulospinal tract (MVST).

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37
Q

Where do MVST and LVST arise?

A

From the vestibular nuclei (lateral and medial) in the floor of the fourth ventricle of the pons and medulla.

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38
Q

Where do two inputs to the vestibular nuclei come from?

A

Vestibular component of CN VIII and the cerebellum

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39
Q

Which pathways are sometimes called postural pathways?

A

Vestibulospinal tract pathways

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40
Q

Activity of the MVST and LVST are important for what two postural things?

A

Support of body against gravity and maintenance of upright posture

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41
Q

In addition to the descending MVST and LVST outputs from the lateral nuclei, what is another output?

A

An ascending output by way of the ascending portion of the medial longitudinal fasciculus (MLF).

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42
Q

Where does the ascending pathway from the lateral nuclei project to?

A

Motor nuclei of CN III, IV, VI for coordination of the eye and head movements in the vestibuloocular reflex

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43
Q

What to LVST neurons act on?

A

Interneurons that facilitate extensor alpha and gamma motor neurons of the LE and flexors of the UE

44
Q

Which muscle groups are antigravity muscles?

A

Extensors of LE and Flexors of UE

45
Q

What is the primary antigravity pathway?

A

LVST

46
Q

What does the LVST pass thru in the spinal cord?

A

The anterior funiculus

47
Q

What does the MVST pass thru in the spinal cord?

A

The descending portion of the MLF to terminate primarily on motor neurons in the cervical and upper thoracic levels

48
Q

What is the primary function of the MVST?

A

To inhibit upper extremity extensors and facilitate flexors

49
Q

Where do tectospinal tract cell bodies arise?

A

Superior colliculus of the midbrain tectum

50
Q

Where do all fibers of the tectospinal tract cross?

A

In the tegmentum of the midbrain

51
Q

What does the tectospinal tract pass thru to get to its terminal interneurons?

A

The descending portion of the MLF running along with the MVST in the upper cervical spine

52
Q

What is the function of the tectospinal tract?

A

To mediate reflex postural movements of the head and neck in response to novel visual stimuli (keeping eyes on something while being able to move your neck)

53
Q

What are the two lateral motor systems (descending pathways)?

A

Lateral corticospinal tract and Rubrospinal tract

54
Q

What are the medial motor systems (descending pathways)?

A

Anterior corticospinal tract, Vestibulospinal (MVST, LVST) tracts, Reticulospinal (Pontine and Medullary) tracts, Tectopspinal tracts

55
Q

Which descending pathways run the entire length of the spinal cord?

A

Lateral corticospinal tract, LVST, Reticulospinal tracts (pontine and medullary)

56
Q

Which descending pathways terminate at the cervical region of the spinal cord?

A

Rubrospinal and Tectospinal tracts

57
Q

Which descending pathways terminate at the cervical and upper thoracic region of the spinal cord?

A

Anterior corticospinal tract and MVST

58
Q

Which descending pathways do not decussate?

A

Anterior corticospinal tract, MVST and LVST, Reticulospinal (pontine and medullary)

59
Q

What is the difference between paresis and paralysis?

A

Paresis is partial paralysis or weakness and occurs when only one or two ventral roots are damaged.
Paralysis is when all roots innervating a particular muscle are destroyed

60
Q

Why will most spinal cord injuries affect control of bladder and bowel?

A

These are innervated by very low spinal cord segments (S2, S3, S4) and so will have been affected by any injury above this point

61
Q

The basal ganglia is a collection of gray matter in what two regions of the brain?

A

Diencephalon and mesencephalon

62
Q

The basal ganglia has its main inputs from what two parts of the brain?

A

The cortex and thalamus

63
Q

T/F The basal ganglia plays an important role in motor control

A

True

64
Q

Besides motor control. the BG also plays a role in what other brain functions?

A

Control of eye movements, cognitive functions, emotional functions

65
Q

T/F BG have no direct connections to the motor neurons in the spinal cord

A

True

66
Q

Does direct stimulation of the BG cause movements?

A

No

67
Q

What are the four motor functions of the BG motor channel?

A

Formulation of general motor plans, Execution of specific motor plans, Scaling of motor intensity, Automatic execution of learned motr plans

Mnemonic: FESA

68
Q

What areas form the largest part of the BG?

A

The caudate, putamen, globus pallidus

69
Q

What two areas of the BG receive the main inputs?

A

Caudate and Putamen

70
Q

Besides the cortex and thalamus, what is another source of significant input to the BG?

A

Substantia nigra pars compacta (dopaminergic)

71
Q

What parts of the BG provide the main outputs?

A

Globus pallidus interna and substantia nigra pars reticula

72
Q

The main inputs to the BG are excitatory, while the main outputs are _______

A

inhibitory

73
Q

Where do the main outputs of the BG project to in the thalamus?

A

the VL and VA

74
Q

Besides the thalamus, where do the main outputs of the BG project to?

A

The reticular formation, superior colliculus

75
Q

What is the third BG pathway, besides the direct and indirect pathways?

A

Substantia nigra circuit

76
Q

What does the substantia nigra circuit do?

A

Helps to modulate activity of the direct and indirect pathways

77
Q

The direct pathway of the BG is also known as?

A

The excitatory pathway

78
Q

What is the result of the direct BG pathway?

A

Caudate/putamen disinhibition of the thalamus

79
Q

What does the caudate/putamen disinhibition of the thalamus lead to?

A

Increased thalamic excitation of the cortex and increased cortical output

80
Q

What is the result of the indirect BG pathway?

A

Caudate/putamen disinhibition of the subthalamic nucleus

81
Q

What does the caudate/putamen disinhibition of the subthalamic nucleus lead to?

A

Leads to globus palidus interna/substantia nigra pars reticulata inhibition of the thalamus

82
Q

What does the inhibition of the thalamus lead to?

A

This decreases thalamic excitation of the cortex and decreases cortical output

83
Q

Where do axons from neurons in the substantia nigra pars compacta synapse?

A

On neurons of the direct and indirect pathways of the caudate and putamen

84
Q

Does the cerebellum have direct connections to spinal cord ventral horn motoneurons

A

No, just like BG

85
Q

From where does the cerebellum receive continuously updated information?

A

Higher brain centers on the intended motor program

86
Q

What do cerebellar diseases and disorders produce?

A

Ataxia, hypotonia to passive stretch, and intention tremors (loss of muscle synergy)

87
Q

What are the four overall functions of the cerebellum?

A

Compare actual and intended movements, planning sequential movements, learning coordinated movements, produce synergy of movement,

88
Q

What is the midline structure of the cerebellum?

A

Vermis

89
Q

What are three deep cerebellar nuclei?

A

Dentate, Globose and Emboliform (interposed), and Fastigial nuclei

90
Q

Which part of the cerebellar peduncle has mainly axons leaving the cerebellum?

A

The superior peduncle

91
Q

The middle and inferior cerebellar peduncles have axons that are mainly _______ the cerebellum.

A

entering

92
Q

What are the two input fiber types to the cerebellum?

A

Mossy fibers and climbing fibers

93
Q

Mossy fibers make up what four types of tracts?

A

Cortico-ponto-cerebellar, dorsal (DSCT) and Ventral (VSCT) spinocerebellar tracts, spinocuneocerebellar tract and rostral spinocerebellar tract, and vestibular nerve.

94
Q

Where to the cortico-ponto-cerebellar tract axons enter the cerebellum?

A

Via the middle cerebellar peduncle

95
Q

What are the three layers of the cerebellar cortex?

A

Molecular, Purkinje cell, and Granular cell layers

96
Q

What are the five types of the cerebellar cortex?

A

Stellate cells, basket cells, Purkinje cells, granule cells, and Golgi cells

97
Q

What are the three functionally significant areas of the cerebellar cortex?

A

Vestibulocerebellum, spinocerebellum, cerebrocerebellum

98
Q

What are the inputs to the vestibulocerebellum?

A

From the inner ear and visual system via the inferior cerebral peduncle

99
Q

What are the outputs from the vestibulocerebellum?

A

Via the fastigial nucleus through the superior and inferior cerebellar pedunclesto the vestibular nuclei

100
Q

What are the inputs to the spinocerebellum?

A

From the spinal cord via the superior and inferior cerebellar peduncle

101
Q

What are the outputs to the spinocerebellum?

A

Via the globose nd emboliform (interposed) nuclei through the superior cerebellar peduncle to the reticular formation, contralateral thalamus, and contralateral red nucleus

102
Q

What are the inputs to the cerebrocerebellum?

A

From the cerebral cortex via the middle cerebellar peduncle

103
Q

What are the outputs to the cerebrocerebellum?

A

via the dentate nucleus through the superior cerebellar peduncle to the contralateral thalamus

104
Q

What is the primary pathway shift in Huntington’s Disease?

A

Direct Pathway, D1

105
Q

What is the primary pathway shift in Parkinson’s Disease?

A

Indirect pathway, D2

Neuroscience (10 decks)

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