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Flashcards in Overview of Motor Systems Deck (28):
1

What do LMNs innervate?

Skeletal Muscle

2

What do the medial LMNs innervate?

Axial/Trunk Muscles

3

What do the lateral LMNs innervate?

Distal Limb Muscles

4

What do the dorsal LMNs innervate?

Flexor Muscles

5

What do the ventral LMNs innervate?

Extensor Muscles

6

What neurotransmitter do LMNs use?

Acetylcholine

7

What are the types of motor units?

S-Unit
FR-Unit
FF-Unit

8

Describe the S-Unit.

Slow twitch fibers that are fatigue resistant

9

Describe the FR-Unit.

Fast twitch fibers that are fatigue resistant

10

Describe the FF-Unit.

Fast twitch fast fatiguing fibers that have high force

11

What are the red muscle fibers?

S-Unit

12

What are the white muscle fibers?

FF-Unit and FR-Unit

13

What are the descending pathways of the LMNs?

Corticospinal tract
Vestibulospinal tract
Reticulospinal tract
Tectospinal tract

14

Describe the corticospinal tract.

All of it is excitatory and uses glutamate as the NT

15

Describe the tectospinal tract.

It supplies the reflex turning of head to visual/auditory stimuli

16

What are the higher cortical centers and their functions?

– Association cortex – “decide” that a movement is needed
– Supplementary motor area – planning/learning complex movements
– Premotor cortex – devise a “plan” for the movement
– Motor cortex – issues “commands” to motor neurons

17

What are Betz cells?

They are large neurons in the motor cortex
and invoked in most leg movements with some hand too

18

What are the contributions to the corticospinal tract?

50% from the primary motor cortex
Adjacent Frontal motor and Parietal areas contribute the rest of the CST fibers

19

Where does the CST project to?

– spinal cord and brainstem
– collaterals (direct and indirect) to basal ganglia, thalamus, reticular formation, sensory nuclei

20

What part of the internal capsule does the CST pass through?

Posterior Limb

21

What is the main distinction in an UMN and LMN lesion in the face on CN VII?

UMN of CN VII are bilateral, however, the LMN are unilateral. Thus, the main distinction between an UMN and LMN lesion is that in the former, there is hemiplegia of the contralateral mid- and lower-face, whereas in the latter, there is complete hemiplegia of the ipsilateral face.

22

Where do UMNs for cranial nerve nuclei descend?

Anterior to the corticospinal tract

23

What nerves receive no direct corticobulbar innervation?

CN 3, 4, 6. So specific collections of neurons in the brainstem control the movements of them.

24

What makes up large MNs? Small MNs?

Large MN - FF-Unit
Small MN - S-Unit

25

What are the parts of the internal capsule?

Anterior Limb
Genu
Posterior Limb

26

Describe LMN Syndrome.

Muscles become weak and atrophic. Sometimes twitches in the muscles may develop as well.

Caused as a result of damaged anterior horn cells.

27

Describe UMN Syndrome.

Damaged UMNs, often caused by stroke. Muscles become stiffened and atrophic after time, but no twitches develop.

28

Damage to what systems will not result in weakness?

Cerebellum
Association Cortex
Basal Ganglia