Descending Motor Pathways Part I

Question 1

In humans when do the earliest tracts of nerve fibers appear

Answer 1

About 2nd fetal month (8 weeks)

Question 2

When do major descending motor tracts appear

Answer 2

About 5th fetal month

Question 3

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

Answer 3

About the middle of fetal life

Question 4

What tracts myelinate first

Answer 4

The oldest tracts

Question 5

When does the corticospinal tract begin to myelinate

Answer 5

3rd trimester

Question 6

When do most of the tracts myelinate

Answer 6

2 years after birth

Question 7

True or False:

Some tracts aren’t completely myelinated for 20 years

Answer 7

True

Question 8

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

Answer 8

Funiculus

Question 9

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

Answer 9

Fasciculus

Question 10

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

Answer 10

Lemniscus

Question 11

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

Answer 11

Tract

Question 12

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

Answer 12

Pathway

Question 13

What makes up the association cortex

Answer 13

Everything that isn’t primary

Question 14

What lobe is the precentral gyrus part of

Answer 14

Frontal

Question 15

What cell bodies are in the precentral gyrus

Answer 15

Lateral corticospinal tract

Question 16

True or False:

There is more brain devoted to movement than anything else

Answer 16

True

Question 17

Where is the supplemental motor area

Answer 17

Immediately anterior to primary motor cortex

Question 18

What is the supplemental motor area responsible for

Answer 18

Planning/programming of motor movements

Question 19

Does the supplemental motor area program the motor commands for speech

Answer 19

Nope

Question 20

What programs the motor commands for speech

Answer 20

Broca’s area

Question 21

True or False:

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

Answer 21

True

Question 22

Where does the premotor area project

Answer 22

Directly to the spinal cord

Question 23

What is the premotor area thought to play a role in

Answer 23

Spatial and sensory guidance of movement

Question 24

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

Answer 24

1. Precentral gyrus
2. Supplemental motor area
3. Premotor area

Question 25

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

Answer 25

1. Postcentral gyrus | 2. Parietal association cortex

Question 26

What lobe is the post central gyrus a part of

Answer 26

Parietal lobe

Question 27

Where do most of the projections of the postcentral gyrus go

Answer 27

Brodmann area 3

Question 28

What is another name for the parietal association cortex

Answer 28

Posterior association cortex

Question 29

Where is the parietal association cortex located

Answer 29

Immediately posterior to the primary somatosensory cortex

Question 30

What does the parietal association cortex play an important role in

Answer 30

Planned movements

Question 31

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

Answer 31

Fibers located medially

Question 32

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

Answer 32

Fasciculus gracilis

Question 33

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

Answer 33

Fibers located laterally

Question 34

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

Answer 34

Fasciculus cuneatus

Question 35

True or False: | Sensory neurons in the dorsal root have bifurcating axons

Answer 35

True

Question 36

What do the 2 branches do

Answer 36

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

Question 37

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

Answer 37

It increases

Question 38

Why do you almost never see paralysis

Answer 38

Due to parallel processing

Question 39

What does bulbar mean

Answer 39

Medulla

Question 40

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

Answer 40

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

Question 41

What are the side loops that modify cortical output

Answer 41

1. Basal ganglia | 2. Cerebellum

Question 42

Does the basal ganglia coordinate or gate movement

Answer 42

Gates

Question 43

Does the cerebellum coordinate or gate movement

Answer 43

Coordinates

Question 44

What is an upper motor neuron

Answer 44

Cortical neuron (from the cortex)

Question 45

What is a lower motor neuron

Answer 45

A neuron that synapses with an UMN

Question 46

What is needed for movement

Answer 46

1 UMN and 1 LMN

Question 47

True or False: | The cortex projects motor fibers that don't synapse on the spinal cord

Answer 47

True, the corticobulbar tract

Question 48

True or False: | Activity in the UMN may facilitate or inhibit the LMN

Answer 48

True

Question 49

Can indicate damage to an UMN

Answer 49

Babinski sign

Question 50

What do LMN do

Answer 50

Triggers a contraction in innervated muscle

Question 51

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

Answer 51

``` Weakness: Yes Atrophy: No Fasciculations: No Reflexes: Increased Tone: Increased ```

Question 52

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

Answer 52

``` Weakness: Yes Atrophy: Yes Fasciculations: Yes Reflexes: Decreased Tone: Decreased ```

Question 53

What are fasciculations

Answer 53

Twitches

Question 54

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

Answer 54

Pyramidal and extrapyramidal

Question 55

What makes a descending motor pathway pyramidal

Answer 55

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

Question 56

What makes a descending motor pathway extrapyramidal

Answer 56

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

Question 57

Where do the medial descending motor systems terminate

Answer 57

On ventromedial neurons

Question 58

What do the medial descending motor systems innervate

Answer 58

Trunk and girdle muscles

Question 59

What is the medial descending motor system more concerned with

Answer 59

Postural control

Question 60

Where do the lateral descending motor systems terminate

Answer 60

On dorsolateral neurons

Question 61

What do the lateral descending motor systems innervate

Answer 61

Distal muscles of the limbs

Question 62

What is the lateral descending motor system more concerned with

Answer 62

Controlling fine voluntary movements of the extremities

Question 63

Where do the lateral corticospinal tract originate

Answer 63

Primary motor cortex and other frontal and parietal areas

Question 64

Where do the lateral corticospinal tract decussate

Answer 64

Pyramidal decussation

Question 65

Where do the lateral corticospinal tract terminate

Answer 65

Entire cord (dominant at cervical and lumbar enlargements)

Question 66

What is the function of the lateral corticospinal tract

Answer 66

Movement of the contralateral limbs

Question 67

Where does the rubrospinal tract descending motor systems originate

Answer 67

Magnocellular division of the red nucleus

Question 68

Where does the rubrospinal tract decussate

Answer 68

Ventral tegmental decussation in the midbrain

Question 69

Where does the rubrospinal tract terminate

Answer 69

Cervical cord

Question 70

What is the function of the rubrospinal tract

Answer 70

Movement of the contralateral limbs

Question 71

What is the site of origin of the anterior corticospinal tract

Answer 71

Primary motor cortex and supplementary motor areas

Question 72

Where does the anterior corticospinal tract terminate

Answer 72

Cervical and upper thoracic cord

Question 73

What is the function of the anterior corticospinal tract

Answer 73

Control of bilateral axial and girdle muscls

Question 74

What is the origin of the vestibulospinal tracts (VST)

Answer 74

Medial VST: Medial and inferior vestibular nuclei | Lateral VST: Lateral vestibular nucleus

Question 75

Where do the vestibulospinal tracts terminate

Answer 75

Medial VST: Cervical and upper thoracic cord | Lateral VST: Entire cord

Question 76

What are the functions of the vestibulospinal tracts

Answer 76

Medial VST: Positioning of the head and neck | Lateral VST: Balance

Question 77

Where do the reticulospinal tracts originate

Answer 77

Pontine and medullary reticular formation

Question 78

Where do the reticularspinal tracts terminate

Answer 78

Entire cord

Question 79

What are the functions of the reticularspinal tracts

Answer 79

Automatic posture and gait related movements

Question 80

Where does the tectospinal tract originate

Answer 80

Superior colliculus

Question 81

What is the site of decussation of the tectospinal tract

Answer 81

Dorsal tegmentum decussation in the midbrain

Question 82

Where does the tectospinal tract terminate

Answer 82

Cervical cord

Question 83

What is the function of the tectospinal tract

Answer 83

Coordination of head and eye movement

Question 84

What are the lateral descending motor systems (2)

Answer 84

1. Lateral corticospinal tract | 2. Rubrospinal tract

Question 85

What are the medial descending motor systems (4)

Answer 85

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