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Flashcards in Descending motor systems Deck (40):
1

what part of the brain does the descending upper motor neuron travel through to get to the brain stem

internal capsule of white matter

2

what is the function of lower motor neurons

directly signals and innervate muscle to contract

3

what is the function of upper motor neurons

send signal from the motor cortex to the lower motor neuron down an axon

4

what would be the results of a lesion in a lower motor neuron

-atonia
-areflexia (loss of knee reflex)
-flaccid paralysis
-fasiculations (twitching)
-severe atrophy

5

what would be the result of a lesion in an upper motor neuron

-spastic paralysis
-hypertonia
-hyperflexia
-mild atrophy
-pathologic reflexes (Babinski sign)

6

what is the Babinski sign and what causes it ?

big toe dorsoflexion w/fanning of other toes when side of heel it stroked, cause by upper motor neuron lesion

7

what horn would you find motor neuron cell bodies

anterior horn/ventral horn

8

what horn would you find somatosensory cell bodies

posterior horn/dorsal horn

9

nuerons controlling axial muscles tend to stay ____ and those controlling distal muscles tend to stay _____ in the anterior horn

medial, lateral

10

neurons controlling flexor mm. are located ______ to the extensor muscle neurons in the anterior horn

posterior

11

what is a motor unit ?

1 motor neuron + all myofibers it innervates

12

which type of muscle (small or large) demonstrates a very small amount of myofibers innervated by 1 motor unit

small ( extraoccular m. has fine movement so must have small number of myofiber innervated by 1 motor unit)

13

functionally what are the 3 types of muscle fibers

standing, running, walking

14

What are the characteristics of type 1 muscle fibers and what is its function

slow twitch, high lipids low sugar, red oxidative (lots of mitochondria)
-used for standing
-dark meat

15

what are the characteristics of type 2 muscle fibers and what is its function

fast twitch, low lipids high sugar, white glycolytic (little mitochondria
-used for running and jumping
-white meat

16

what are the 3 regions of the brain that influence (plan/monitor) upper motor neuron output but have NO direct effect on lower motor neurons

basal ganglia
association cortex
cerebellum

17

what is the difference b/w hierarchial motor control and parallel motor control

Hierarchial - premotor cortex tells motor cortex and the LMN what to do
Parallel - premotor cortex directly talks to LMN what to do

18

motor nuerons are found on the _____ horn, but terminate or synapse on the _____ horn

anterior/ventral horn
posterior/dorsal horn

19

what are the 3 main descending motor pathways

-corticospinal tract
-corticobulbar tract
-corticopontine tract

20

where is the primary motor cortex

precentral gyrus (area 4)

21

where is the primary somatosensory cortex

postcentral gyrus (3,1,2)

22

T/F the corticospinal tract originates in the primary motor area only ?

False, originates in the primary motor area, somatosensory area, premotor area, supp. motor area, and superior parietal lobule

23

what does the primary motor area control

contralateral, voluntary fine digital movements

24

where is the premotor area and what does it control

lateral aspect of area 6
-plans movements/gives instructions to motor cortex in response to an external stimulus

25

what would a lesion in the primary motor area cause

complete paralysis of contralateral musculature

26

what would a lesion in the premotor area cause

-moderate weakness of contralateral musculature
-loss ability to associate hand movements to visual or verbal cues

27

where is the supplemental motor area and what is its function

medial aspect of area 6 (premotor area is lateral)
-plans movements while thinking, "imagines/visualizes" movements

28

though the corticospinal tract is a "complex tract", what movement would be permanently loss if you were to cut it

fine finger movement

29

where does the corticospinal tract decussate at ?

spinomedullary junction (85 %)

30

85 % of the lateral corticospinal tract decussates at the spinomedullary junction and descends to where ?

lateral funiculus

31

the anterior corticospinal tract that does NOT decussate (15%) descends to _________ and controls what muscle activity

anterior funiculus
-axial muscle activity

32

a lesion in the corticospinal tract in the brain would cause what type of muscle weakness ipsilateral or contralateral

contralateral cuz it decussates at spinomedullary junction

33

what does the rubrospinal tract control

shoulder and proximal arm mm

34

what does the reticulospinal tract control

rhythmic motor actions like walking

35

what does the vestibulospinal tract control

balance (why cats land on feet)

36

what does the tectospinal tract control

head turning

37

the corticobulbar pathway ends on what CN nuclei, and specifically what CN recieve no input

V, VII, X, XI, XII
No input - III, IV, VI (all eye muscles)

38

the corticobulbar path has what type of decussation and what type of input ?

Has No decussation so bilateral input

39

what CN is the exception to the typical corticobulbar pathway

CN V
-upper face innervate bilaterally
-BUT lower face (lips) innervated ipsilaterally

40

unilateral damage to CN V of the corticobulbar pathway would result in ?

-inability to smile symmetrically (only lower facial muscles affected cuz upper face can still recieve input from other side since its inervated bilaterally)