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Neuroanatomy Lecture > Motor System > Flashcards

Motor System Flashcards

1
Q

What are the general functions of the motor system?

A

reflexes, posture, balance, locomotion, and directed movement

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2
Q

What types of neurons are associated with the motor system?

A

lower motor neurons, inter neurons, and upper motor neurons

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3
Q

What do lower motor neurons release?

A

acetylcholine onto skeletal muscles to nicotinic receptors

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4
Q

Where are lower motor neurons located?

A

on the ventral horn of the spinal cord

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5
Q

What is the function of lower motor neurons?

A

the innervate skeletal muscles to excite them

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6
Q

Where are inter neurons located?

A

in the grey matter of the spinal cord

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7
Q

What do inter neurons innervate?

A

lower motor neurons

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8
Q

True or false: Inter neurons are only inhibitory.

A

False, they are either excitatory or inhibitory

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9
Q

What do upper motor neurons innervate?

A

inter neurons

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10
Q

What do the upper motor neurons in the motor cortex control?

A

directed movement

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11
Q

What do the upper motor neurons in the reticular formation control?

A

posture

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12
Q

What do the upper motor neurons in the vestibular nuclei control?

A

balance

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13
Q

Are upper motor neurons excitatory or inhibitory?

A

excitatory

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14
Q

What is the purpose of the central pattern generators involved in locomotion?

A

they are a network if neurons in the spinal cord at each limb that move the foot forward, plant the foot on the ground, and move the foot backward

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15
Q

What descending motor tracts are associated with the motor system and the cortex?

A

the corticonuclear tract and corticospinal tract

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16
Q

Where does the corticonuclear tract begin?

A

in the primary motor cortex

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17
Q

Where does the corticonuclear tract terminate?

A

in the motor nuclei of CN III, IV, V, VI, VIII, XI, and XII and the nucleus ambiguous

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18
Q

Where does the corticospinal tract begin and end?

A

it begins in the primary motor cortex and terminates in the spinal cord where it innervates inter motor neurons

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19
Q

What structures does the corticospinal tract run through?

A

the internal capsule, crus cerebri, and the pyramids

20
Q

What percent of the corticospinal tract crosses at the pyrimidal dessucation and what does it become?

A

75% and the lateral corticospinal tract

21
Q

What percent of the corticospinal tract descends ipsilaterally at the pyrimidal dessucation and what does it become?

A

25% and the ventral corticospinal tract

22
Q

What systems are associated with coordination of voluntary movements?

A

the primary cortex, somesthetic cortex, visual, and auditory

23
Q

What do all of the systems associated with coordinated volunary movements communicate through?

A

the internal capsule

24
Q

What is the Renshaw cell’s involvement in feedback inhibition?

A

it is a special local-circuit interneuron that inhibits mostly lower motor neurons that innervate extensor muscles

25
Q

How does tetanus toxin effect renshaw cells?

A

they make them unable to provide feedback inhibition

26
Q

Explain inter segmental modulation by using the stretch reflex?

A

the stretching of a muscle spindle causes muscle contraction and inhibition of the opposing muscle group

27
Q

What motor tracts run in the lateral funiculus?

A

the lateral corticospinal tracts, rubrospinal tract, and medullary reticulospinal tract

28
Q

What is the function of the motor tracts that run in the lateral funiculus?

A

excites flexors and inhibit extensors

29
Q

What motor tracts run in the ventral funiculus?

A

pontine reticulospinal, ventral corticospinal, and vestibulospinal tracts

30
Q

What is the function of the motor tracts that run in the ventral funiculus?

A

they excite the extensors and inhibit flexors

31
Q

What are extensors also known as?

A

anti-gravity muscles

32
Q

What muscles are involved with the maintenance of posture?

A

the anti-gravity muscles

33
Q

How do the antigravity muscles maintain posture?

A

they modulate the stretch reflex

34
Q

What is the modulation of the stretch reflex determined by?

A

the reticular formation

35
Q

What system is associated with balance?

A

the vestibular system

36
Q

What spinal tracts are associated with balance?

A

lateral and medial vestibulospinal

37
Q

What is the function of the spinal tracts associated with balance?

A

to excite extensors and inhibit flexors

38
Q

What clinical signs are associated with lower motor neuron disease?

A

paresis/paralysis, hyporeflexia/areflexia, and hypotonia/atonia

39
Q

What toxins affect lower motor neurons?

A

tick paralysis and botulinum toxin

40
Q

How does tick paralysis affect lower motor neurons?

A

it impairs/disables them leading to paresis/paralysis

41
Q

How does botulinum toxin affect lower motor neurons?

A

it inhibits transmitter release from lower motor neurons which leads to reduced/lack of communication between LMN and muscle

42
Q

What is effected in upper motor neuron disease?

A

the descending tracts are most lukely lesioned

43
Q

What are the clinical signs associated with upper motor neuron disease?

A

abnormal gait, paresis/paralysis, hyperreflexia, and hypertonia

44
Q

What is an example of upper motor neuron disease?

A

prion disease

45
Q

What are some examples of prion disease?

A

bovine spongiform encephalopathy, scrapie, chronic wasting disease

Neuroanatomy Lecture (17 decks)

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