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Exam 3 Motor system Flashcards

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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
Where does the red nucleus receive input from?
The cerebral cortex and cerebellum
26
Which two tracts are alternate routes for achieving voluntary movements?
The rubrospinal and reticulospintal tracts
27
What are the two reticulospinal tracts?
Pontine (medial) and Medullary (lateral) reticulospinal tracts
28
What does the medullary reticulospinal tract pass thru in the spinal cord?
Anterior funiculus to all spinal levels
29
T/F The medullary reticulospinal tract descends both crossed and uncrossed down the spine.
True
30
What type of neurons does medullary reticulospinal tract act on mostly?
Primarily on gamma motor neurons, but also on alpha
31
What is the general function of the medullary reticulospinal tract thought to be?
Inhibit lower extremity extensors and facilitate flexors, reducing muscle tone in the lower extremities
32
The pontine reticulospinal tract descends mostly ________ in the anterior funiculus of the spinal cord to all spinal levels.
Uncrossed
33
While the medullary reticulospinal tract descend both _______ and ________, the pontine reticulospinal tract descends mostly uncrossed.
crossed and uncrossed
34
What is the function of the pontine reticulorspinal tract?
It facilitates lower extremity extensor motor neurons, increasing muscle tone
35
The medullary reticulospinal tract ________ (inhibits/facilitates) lower extermity extensors (LE), while the pontine reticulospinal tract _______ (inhibits/facilitates) the LE extensors
Inhibits; facilitates
36
What are the two vestibulospinal tracts?
Lateral vestibulospinal tract (LVST) and medial vestibulospinal tract (MVST).
37
Where do MVST and LVST arise?
From the vestibular nuclei (lateral and medial) in the floor of the fourth ventricle of the pons and medulla.
38
Where do two inputs to the vestibular nuclei come from?
Vestibular component of CN VIII and the cerebellum
39
Which pathways are sometimes called postural pathways?
Vestibulospinal tract pathways
40
Activity of the MVST and LVST are important for what two postural things?
Support of body against gravity and maintenance of upright posture
41
In addition to the descending MVST and LVST outputs from the lateral nuclei, what is another output?
An ascending output by way of the ascending portion of the medial longitudinal fasciculus (MLF).
42
Where does the ascending pathway from the lateral nuclei project to?
Motor nuclei of CN III, IV, VI for coordination of the eye and head movements in the vestibuloocular reflex
43
What to LVST neurons act on?
Interneurons that facilitate extensor alpha and gamma motor neurons of the LE and flexors of the UE
44
Which muscle groups are antigravity muscles?
Extensors of LE and Flexors of UE
45
What is the primary antigravity pathway?
LVST
46
What does the LVST pass thru in the spinal cord?
The anterior funiculus
47
What does the MVST pass thru in the spinal cord?
The descending portion of the MLF to terminate primarily on motor neurons in the cervical and upper thoracic levels
48
What is the primary function of the MVST?
To inhibit upper extremity extensors and facilitate flexors
49
Where do tectospinal tract cell bodies arise?
Superior colliculus of the midbrain tectum
50
Where do all fibers of the tectospinal tract cross?
In the tegmentum of the midbrain
51
What does the tectospinal tract pass thru to get to its terminal interneurons?
The descending portion of the MLF running along with the MVST in the upper cervical spine
52
What is the function of the tectospinal tract?
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
What are the two lateral motor systems (descending pathways)?
Lateral corticospinal tract and Rubrospinal tract
54
What are the medial motor systems (descending pathways)?
Anterior corticospinal tract, Vestibulospinal (MVST, LVST) tracts, Reticulospinal (Pontine and Medullary) tracts, Tectopspinal tracts
55
Which descending pathways run the entire length of the spinal cord?
Lateral corticospinal tract, LVST, Reticulospinal tracts (pontine and medullary)
56
Which descending pathways terminate at the cervical region of the spinal cord?
Rubrospinal and Tectospinal tracts
57
Which descending pathways terminate at the cervical and upper thoracic region of the spinal cord?
Anterior corticospinal tract and MVST
58
Which descending pathways do not decussate?
Anterior corticospinal tract, MVST and LVST, Reticulospinal (pontine and medullary)
59
What is the difference between paresis and paralysis?
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
Why will most spinal cord injuries affect control of bladder and bowel?
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
The basal ganglia is a collection of gray matter in what two regions of the brain?
Diencephalon and mesencephalon
62
The basal ganglia has its main inputs from what two parts of the brain?
The cortex and thalamus
63
T/F The basal ganglia plays an important role in motor control
True
64
Besides motor control. the BG also plays a role in what other brain functions?
Control of eye movements, cognitive functions, emotional functions
65
T/F BG have no direct connections to the motor neurons in the spinal cord
True
66
Does direct stimulation of the BG cause movements?
No
67
What are the four motor functions of the BG motor channel?
Formulation of general motor plans, Execution of specific motor plans, Scaling of motor intensity, Automatic execution of learned motr plans Mnemonic: FESA
68
What areas form the largest part of the BG?
The caudate, putamen, globus pallidus
69
What two areas of the BG receive the main inputs?
Caudate and Putamen
70
Besides the cortex and thalamus, what is another source of significant input to the BG?
Substantia nigra pars compacta (dopaminergic)
71
What parts of the BG provide the main outputs?
Globus pallidus interna and substantia nigra pars reticula
72
The main inputs to the BG are excitatory, while the main outputs are _______
inhibitory
73
Where do the main outputs of the BG project to in the thalamus?
the VL and VA
74
Besides the thalamus, where do the main outputs of the BG project to?
The reticular formation, superior colliculus
75
What is the third BG pathway, besides the direct and indirect pathways?
Substantia nigra circuit
76
What does the substantia nigra circuit do?
Helps to modulate activity of the direct and indirect pathways
77
The direct pathway of the BG is also known as?
The excitatory pathway
78
What is the result of the direct BG pathway?
Caudate/putamen disinhibition of the thalamus
79
What does the caudate/putamen disinhibition of the thalamus lead to?
Increased thalamic excitation of the cortex and increased cortical output
80
What is the result of the indirect BG pathway?
Caudate/putamen disinhibition of the subthalamic nucleus
81
What does the caudate/putamen disinhibition of the subthalamic nucleus lead to?
Leads to globus palidus interna/substantia nigra pars reticulata inhibition of the thalamus
82
What does the inhibition of the thalamus lead to?
This decreases thalamic excitation of the cortex and decreases cortical output
83
Where do axons from neurons in the substantia nigra pars compacta synapse?
On neurons of the direct and indirect pathways of the caudate and putamen
84
Does the cerebellum have direct connections to spinal cord ventral horn motoneurons
No, just like BG
85
From where does the cerebellum receive continuously updated information?
Higher brain centers on the intended motor program
86
What do cerebellar diseases and disorders produce?
Ataxia, hypotonia to passive stretch, and intention tremors (loss of muscle synergy)
87
What are the four overall functions of the cerebellum?
Compare actual and intended movements, planning sequential movements, learning coordinated movements, produce synergy of movement,
88
What is the midline structure of the cerebellum?
Vermis
89
What are three deep cerebellar nuclei?
Dentate, Globose and Emboliform (interposed), and Fastigial nuclei
90
Which part of the cerebellar peduncle has mainly axons leaving the cerebellum?
The superior peduncle
91
The middle and inferior cerebellar peduncles have axons that are mainly _______ the cerebellum.
entering
92
What are the two input fiber types to the cerebellum?
Mossy fibers and climbing fibers
93
Mossy fibers make up what four types of tracts?
Cortico-ponto-cerebellar, dorsal (DSCT) and Ventral (VSCT) spinocerebellar tracts, spinocuneocerebellar tract and rostral spinocerebellar tract, and vestibular nerve.
94
Where to the cortico-ponto-cerebellar tract axons enter the cerebellum?
Via the middle cerebellar peduncle
95
What are the three layers of the cerebellar cortex?
Molecular, Purkinje cell, and Granular cell layers
96
What are the five types of the cerebellar cortex?
Stellate cells, basket cells, Purkinje cells, granule cells, and Golgi cells
97
What are the three functionally significant areas of the cerebellar cortex?
Vestibulocerebellum, spinocerebellum, cerebrocerebellum
98
What are the inputs to the vestibulocerebellum?
From the inner ear and visual system via the inferior cerebral peduncle
99
What are the outputs from the vestibulocerebellum?
Via the fastigial nucleus through the superior and inferior cerebellar pedunclesto the vestibular nuclei
100
What are the inputs to the spinocerebellum?
From the spinal cord via the superior and inferior cerebellar peduncle
101
What are the outputs to the spinocerebellum?
Via the globose nd emboliform (interposed) nuclei through the superior cerebellar peduncle to the reticular formation, contralateral thalamus, and contralateral red nucleus
102
What are the inputs to the cerebrocerebellum?
From the cerebral cortex via the middle cerebellar peduncle
103
What are the outputs to the cerebrocerebellum?
via the dentate nucleus through the superior cerebellar peduncle to the contralateral thalamus
104
What is the primary pathway shift in Huntington's Disease?
Direct Pathway, D1
105
What is the primary pathway shift in Parkinson's Disease?
Indirect pathway, D2

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