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Neuro 2 > Descending Motor Pathways Part I > Flashcards

Descending Motor Pathways Part I Flashcards

1
Q

In humans when do the earliest tracts of nerve fibers appear

A

About 2nd fetal month (8 weeks)

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2
Q

When do major descending motor tracts appear

A

About 5th fetal month

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3
Q

When does sheathing of the spinal cord’s nerve fibers begin

A

About the middle of fetal life

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4
Q

What tracts myelinate first

A

The oldest tracts

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5
Q

When does the corticospinal tract begin to myelinate

A

3rd trimester

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6
Q

When do most of the tracts myelinate

A

2 years after birth

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7
Q

True or False:

Some tracts aren’t completely myelinated for 20 years

A

True

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8
Q

What is a morphological term to describe a large group of nerve fibers which are located in a given area

A

Funiculus

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9
Q

What is a bundle or cluster; morphological; within a funiculus, groups of fibers from diverse origins which share common features are sometimes arranged in smaller bundles of axons

A

Fasciculus

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10
Q

What is a bundle of secondary sensory fibers in the brainstem which terminate in specific relay nuclei of the diencephalon

A

Lemniscus

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11
Q

What is a group of nerve fibers which usually have the same origin destination course and function

A

Tract

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12
Q

What usually refers to the entire neuronal circuit responsible for a particular function and includes all nuclei and tracts associated with that function

A

Pathway

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13
Q

What makes up the association cortex

A

Everything that isn’t primary

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14
Q

What lobe is the precentral gyrus part of

A

Frontal

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15
Q

What cell bodies are in the precentral gyrus

A

Lateral corticospinal tract

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16
Q

True or False:

There is more brain devoted to movement than anything else

A

True

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17
Q

Where is the supplemental motor area

A

Immediately anterior to primary motor cortex

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18
Q

What is the supplemental motor area responsible for

A

Planning/programming of motor movements

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19
Q

Does the supplemental motor area program the motor commands for speech

A

Nope

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20
Q

What programs the motor commands for speech

A

Broca’s area

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21
Q

True or False:

The premotor area’s role in movement is not completely understood

A

True

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22
Q

Where does the premotor area project

A

Directly to the spinal cord

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23
Q

What is the premotor area thought to play a role in

A

Spatial and sensory guidance of movement

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24
Q

What are the 3 primary and association cortical areas devoted to motor function

A
  1. Precentral gyrus
  2. Supplemental motor area
  3. Premotor area
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25
Q

What are the 2 primary and association cortical areas devoted to sensory function

A
  1. Postcentral gyrus

2. Parietal association cortex

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26
Q

What lobe is the post central gyrus a part of

A

Parietal lobe

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27
Q

Where do most of the projections of the postcentral gyrus go

A

Brodmann area 3

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28
Q

What is another name for the parietal association cortex

A

Posterior association cortex

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29
Q

Where is the parietal association cortex located

A

Immediately posterior to the primary somatosensory cortex

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30
Q

What does the parietal association cortex play an important role in

A

Planned movements

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31
Q

Where in the white matter does information from the lower parts of the body ascend

A

Fibers located medially

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32
Q

What is the area where lower body parts send info up the spinal cord called

A

Fasciculus gracilis

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33
Q

Where in the white matter does information from the upper parts of the body ascend

A

Fibers located laterally

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34
Q

What is the area where upper body parts send info up the spinal cord called

A

Fasciculus cuneatus

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35
Q

True or False:

Sensory neurons in the dorsal root have bifurcating axons

A

True

36
Q

What do the 2 branches do

A

1 brings in info from the periphery and the other carries info into the dorsal aspect of the spinal cord

37
Q

What happens to the proportion of gray matter to white matter as you move down the spinal cord

A

It increases

38
Q

Why do you almost never see paralysis

A

Due to parallel processing

39
Q

What does bulbar mean

A

Medulla

40
Q

What are the 4 steps in the cortical motor areas initiating volitional movements

A
  1. Cortex projects to spinal cord directly through corticospinal tract
  2. Cortex also projects indirectly through relay areas in the brain
  3. The cortical output is modified by 2 parallel but separate side loops
  4. Final common pathway via alpha motor neurons
41
Q

What are the side loops that modify cortical output

A
  1. Basal ganglia

2. Cerebellum

42
Q

Does the basal ganglia coordinate or gate movement

A

Gates

43
Q

Does the cerebellum coordinate or gate movement

A

Coordinates

44
Q

What is an upper motor neuron

A

Cortical neuron (from the cortex)

45
Q

What is a lower motor neuron

A

A neuron that synapses with an UMN

46
Q

What is needed for movement

A

1 UMN and 1 LMN

47
Q

True or False:

The cortex projects motor fibers that don’t synapse on the spinal cord

A

True, the corticobulbar tract

48
Q

True or False:

Activity in the UMN may facilitate or inhibit the LMN

A

True

49
Q

Can indicate damage to an UMN

A

Babinski sign

50
Q

What do LMN do

A

Triggers a contraction in innervated muscle

51
Q

If someone has an UMN lesion do they have weakness, atrophy, fasciculations, reflexes, or tone

A 
Weakness: Yes
Atrophy: No
Fasciculations: No
Reflexes: Increased
Tone: Increased
52
Q

If someone has a LMN lesion do they have weakness, atrophy, fasciculations, reflexes, or tone

A 
Weakness: Yes
Atrophy: Yes
Fasciculations: Yes
Reflexes: Decreased
Tone: Decreased
53
Q

What are fasciculations

A

Twitches

54
Q

What have the descending motor pathway commonly been divided into (2)

A

Pyramidal and extrapyramidal

55
Q

What makes a descending motor pathway pyramidal

A

The descending motor tract originates from the cerebral cortex and passes through the pyramids

56
Q

What makes a descending motor pathway extrapyramidal

A

The descending motor tract originates from the cerebral cortex but does not pass through the pyramids

57
Q

Where do the medial descending motor systems terminate

A

On ventromedial neurons

58
Q

What do the medial descending motor systems innervate

A

Trunk and girdle muscles

59
Q

What is the medial descending motor system more concerned with

A

Postural control

60
Q

Where do the lateral descending motor systems terminate

A

On dorsolateral neurons

61
Q

What do the lateral descending motor systems innervate

A

Distal muscles of the limbs

62
Q

What is the lateral descending motor system more concerned with

A

Controlling fine voluntary movements of the extremities

63
Q

Where do the lateral corticospinal tract originate

A

Primary motor cortex and other frontal and parietal areas

64
Q

Where do the lateral corticospinal tract decussate

A

Pyramidal decussation

65
Q

Where do the lateral corticospinal tract terminate

A

Entire cord (dominant at cervical and lumbar enlargements)

66
Q

What is the function of the lateral corticospinal tract

A

Movement of the contralateral limbs

67
Q

Where does the rubrospinal tract descending motor systems originate

A

Magnocellular division of the red nucleus

68
Q

Where does the rubrospinal tract decussate

A

Ventral tegmental decussation in the midbrain

69
Q

Where does the rubrospinal tract terminate

A

Cervical cord

70
Q

What is the function of the rubrospinal tract

A

Movement of the contralateral limbs

71
Q

What is the site of origin of the anterior corticospinal tract

A

Primary motor cortex and supplementary motor areas

72
Q

Where does the anterior corticospinal tract terminate

A

Cervical and upper thoracic cord

73
Q

What is the function of the anterior corticospinal tract

A

Control of bilateral axial and girdle muscls

74
Q

What is the origin of the vestibulospinal tracts (VST)

A

Medial VST: Medial and inferior vestibular nuclei

Lateral VST: Lateral vestibular nucleus

75
Q

Where do the vestibulospinal tracts terminate

A

Medial VST: Cervical and upper thoracic cord

Lateral VST: Entire cord

76
Q

What are the functions of the vestibulospinal tracts

A

Medial VST: Positioning of the head and neck

Lateral VST: Balance

77
Q

Where do the reticulospinal tracts originate

A

Pontine and medullary reticular formation

78
Q

Where do the reticularspinal tracts terminate

A

Entire cord

79
Q

What are the functions of the reticularspinal tracts

A

Automatic posture and gait related movements

80
Q

Where does the tectospinal tract originate

A

Superior colliculus

81
Q

What is the site of decussation of the tectospinal tract

A

Dorsal tegmentum decussation in the midbrain

82
Q

Where does the tectospinal tract terminate

A

Cervical cord

83
Q

What is the function of the tectospinal tract

A

Coordination of head and eye movement

84
Q

What are the lateral descending motor systems (2)

A
  1. Lateral corticospinal tract

2. Rubrospinal tract

85
Q

What are the medial descending motor systems (4)

A
  1. Anterior corticalspinal tract
  2. Vestibulospinal tracts
  3. Reticulospinal tracts
  4. Tectospinal tract

Neuro 2 (20 decks)

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