Anatomy - Motor Tracts Flashcards Preview

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Flashcards in Anatomy - Motor Tracts Deck (79)
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1

where are upper motor neurons located and where do their axons travel

- what do they synapse with

located in cerebral cortex or brain stem

- axons travel in descending tracts

- synapse with lower motor neurons and/or interneurons of the spinal cord

2

what tracts involve upper motor neurons

corticospinal tract

corticobulbar tract (corticonuclear)

3

where are the cell bodies of lower motor neurons and where do they synapse

cell bodies in spinal cord or brain stem

- synapse with skeletal muscle fibers

4

compare alpha and gamma motor neurons

alpha: large cell bodies, large myelinated axons, project to extrafusal skeletal muscle

gamma: medium sized, myelinated, project to intrafusal fibers of muscle spindle

5

what type neurons are peripheral and cranial nerves

lower motor neurons

6

describe the pathway of the lateral corticospinal tract

cell bodies arise in cortex --> descend through posterior limb of internal capsule --> cerebral peduncles --> anterior pons --> pyramids --> fibers cross in lower medulla --> descends in lateral column of spinal cord --> synapses with lower motor neurons in spinal cord

7

what does the medial corticospinal tract (of the corticospinal tract) encompass

postural muscles (10% of fibers)

- neck, shoulder, and trunk muscles

8

what does the lateral corticospinal tract (of the corticospinal tract) encompass

limb muscles, fractionation (90% of fibers)

9

what is the source of most of the neurons in the corticospinal tract

primary motor cortex

10

in what way (contralaterally/ipsilaterally) does the primary motor cortex control the body

contralaterally

(right side motor strip controls left side of body)

11

compare lateral and medial corticospinal tracts

the medial (anterior) corticospinal tract remains ipsilateral throughout its tract

- lateral tract becomes contralateral in the pyramids before descending into spinal cord

12

arterial supply to trunk/leg region of cortex

arterial supply to hand region of cortex

anterior cerebral a.

middle cerebral a. 

13

blood supply to internal capsule

lenticulostriate arteries (posterior limb)

anterior choroidal artery

14

what artery supplies the midbrain where the corticospinal tract passes

posterior cerebral a.

15

what artery supplies the pons where the corticospinal tract passes through

paramedian branches of basilar a.

16

what artery supplies the medulla where the corticospinal tract passes through

sulcal branches of anterior spinal a. 

17

arterial supply of corticospinal tract in the spinal cord

posterior and anterior spinal arteries

18

where do the axons of the corticobulbar tract arise from

ventral part of cortical area 4

(primary motor complex) (precentral gyrus)

19

describe the path of the corticobulbar tract

ventral part of cortical area 4 --> genu of internal capsule --> cerebral peduncles --> anterior pons --> pyramids --> stops in brainstem at specific motor nucleus

20

how do the axons of the corticobulbar tract travel

they cross to control the muscles on the contralateral side (except for CN 11 which stays ipsilateral and travels with median corticospinal tract)

21

how do the neurons of the corticobulbar tract affect the trigeminal nucleus in the pons

fibers split bilaterally to influence motor trigeminal nuclei

22

how do the neurons of the corticobulbar tract affect the facial nucleus in the pons

the facial motor nucleus that supplies the forehead is influenced bilaterally by the neurons of the corticobulbar tract

- the contralateral lower side of the face is controlled contralaterally

23

how do the neurons of the corticobulbar tract affect the nucleus ambiguus (CN 9 and 10) in the medulla

it influences nucleus ambiguus bilaterally but the actual muscle influence seems to be controlled contralaterally

24

how do the neurons of the corticobulbar tract affect the spinal accessory nucleus in the spinal cord

ipsilaterally

25

how do the neurons of the corticobulbar tract affect the hypoglossal nucleus

contralaterally

26

where are lower motor neurons found

ventral horns

27

in the ventral horn, where are the lower motor neurons for axial muscles, limb muscles, extensor muscles, and flexor muscles

medial: axial muscles

lateral: limb muscles

posterior: flexor muscles

anterior: extensor muscles

28

what are the medial upper motor neuron tracts (4)

tectospinal

medial reticulospinal

lateral vestibulospinal

medial vestibulospinal

29

what are the lateral upper motor neuron tracts (2)

rubrospinal

lateral reticulospinal

30

describe the path of the lateral vestibulospinal tract

starts in superior/lateral vestibular nuclei in the pons --> stays ipsilateral to the spinal cord --> innervates lower motor neurons --> postural muscles and limb extensors (in relation to gravity)

**goes to all spinal cord levels**