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Block 3 Neuro > Week 1 > Flashcards

Week 1 Flashcards

1
Q

function of lower motor neurons in brainstem

A

innervate muscles of head and face

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2
Q

facial nucleus innervates what?

A

muscles of facial expression

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3
Q

relay station for information from basal ganglia or cerebellum to be delivered to the cortex

A

thalamus

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4
Q

name the medial brainstem pathway(s)

A

reticulospinal, vestibulospinal, and tectospinal

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5
Q

name the lateral brainstem pathway(s)

A

rubrospinal

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6
Q

which area of the brain integrates motor movements with sensory input (mainly from the visual system)?

A

premotor cortex

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7
Q

which area of the brain is important in internally-driven, will-driven movements, as well as formulating the intention to make a movement?

A

supplementary motor cortex

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8
Q

what is the function of the lateral corticospinal tract?

A

controls contralateral limb and digit muscles, movement of extremities

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9
Q

what is the function of the anterior corticospinal tract?

A

controls neck and trunk muscles

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10
Q

what are synergistic muscles?

A

muscles that work across the joint together

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11
Q

what is a motor unit?

A

one motor neuron and all of the muscle fibers it innervates

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12
Q

motor neurons communicate with skeletal muscles via what neurotransmitter?

A

acetylcholine

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13
Q

normal muscle: 1 motor neuron innervates muscle fibers in ______ ______ within a muscle

A

different fascicles

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14
Q

pathological muscle: 1 motor neuron innervates many muscle fibers in ______ _______

A

one fascicle

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15
Q

in pathological muscle, the muscle unit is overall much ____

A

larger

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16
Q

why is there fiber type “grouping” in pathological muscle?

A

because some motor units degenerate, and surviving motor units sprout axons that reinnervate the adjacent denervated fibers, inducing a phenotype switch in muscle fibers

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17
Q

in pathological muscle, the number of motor neurons _____

A

decreases

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18
Q

fasciculations happen in what kind of disease?

A

lower motor neuron disease

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19
Q

what are alpha motor neurons also called?

A

lower motor neurons

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20
Q

what is a motor nucleus?

A

a vertical column of motor neurons in the spinal cord that innervate the same muscle

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21
Q

what kind of neurons connect medial motor nuclei?

A

long propriospinal interneurons

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22
Q

what is the role of the medial motor nuclei?

A

they contain motor neurons that innervate axial muscles of the neck, back –> balance, posture

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23
Q

what kind of neurons connect lateral motor nuclei?

A

short propriospinal interneurons

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24
Q

what is the role of the lateral motor nuclei?

A

they contain motor neurons that innervate limb muscles

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25
Q

axon of each motor neuron exits spinal cord through _____ _____ and terminates in muscle

A

ventral root

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26
Q

what kind of neurons are located in the brainstem nuclei that directly innervate and control muscles?

A

lower motor neurons

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27
Q

where do upper motor neurons originate?

A

brainstem and motor cortex

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28
Q

what are premotor neurons also called?

A

upper motor neurons

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29
Q

UMN lesion vs. LMN lesion: weakness

A

both

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30
Q

UMN lesion vs. LMN lesion: atrophy

A

LMN

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31
Q

UMN lesion vs. LMN lesion: fasciculations

A

LMN

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32
Q

UMN lesion vs. LMN lesion: hyperactive reflexes

A

UMN

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33
Q

UMN lesion vs. LMN lesion: hypoactive reflexes

A

LMN

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34
Q

UMN lesion vs. LMN lesion: increased muscle tone

A

UMN

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35
Q

UMN lesion vs. LMN lesion: decreased muscle tone

A

LMN

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36
Q

slow twitch motor units: ____ muscle fibers, ____ motor neuron cell bodies

A

small, small

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37
Q

fast fatigable motor units: ____ muscle fibers, ____ motor neuron cell bodies

A

large, large

38
Q

slow twitch motor units rely on what for energy?

A

oxidative catabolism

39
Q

fast fatigable motor units rely on what for energy?

A

anaerobic catabolism

40
Q

purpose of slow twitch motor units

A

long endurance, posture

41
Q

purpose of fast fatigable motor units

A

strength and speed

42
Q

purpose of fast fatigue-resistant motor units

A

endurance during exertion

43
Q

order of recruitment of motor units

A

slow twitch, fast fatigue-resistant, fast-fatigable

44
Q

muscle spindles sense muscle _____

A

length

45
Q

which muscle receptor is important for proprioception?

A

muscle spindles

46
Q

when do muscle spindles discharge best?

A

when muscle is stretched

47
Q

what are muscle spindles composed of?

A

intrafusal fibers

48
Q

what is the role of intrafusal fibers?

A

they sense the length of muscle and make up muscle spindles

49
Q

what are the names of the muscle spindle sensory afferents?

A

Ia and II

50
Q

Ia afferents innervate which intrafusal fibers and code what?

A

all three types; velocity of stretch

51
Q

II afferents innervate which intrafusal fibers and code what?

A

static bag fibers and nuclear chain fibers; duration of stretch

52
Q

when do intrafusal fibers increase firing rate?

A

when they are stretched

53
Q

when do intrafusal fibers stop firing?

A

when muscle contracts (shortens)

54
Q

what does CNS use muscle spindles for?

A

to sense and correctly change position of limbs and body segments

55
Q

Golgi tendon organs sense muscle ______

A

tension (force)

56
Q

golgi tendon organs are innervated by?

A

Ib afferent neurons

57
Q

muscle spindles are innervated by?

A

Ia and II afferent neurons

58
Q

when do Ib afferent neurons fire?

A

when muscle contracts and golgi tendon organ stretches

59
Q

what does CNS use golgi tendon organs for? (2)

A
  1. give precise control of muscle tension so appropriate force is exerted for task
  2. negative feedback: protective against too much muscle tension and muscle damage
60
Q

passive stretch: status of muscle spindle and golgi tendon organ

A

muscle spindle: stimulated

golgi tendon organ: some stimulation

61
Q

active contraction: status of muscle spindle and golgi tendon organ

A

muscle spindle: silent

golgi tendon organ: stimulated

62
Q

what is the role of gamma motor neurons?

A

to keep muscle spindle sensitive at all muscle lengths

63
Q

what do gamma motor neurons do for alpha motor neurons?

A

provide positive feedback to reinforce activation of alpha motor neurons so muscle contraction continues

64
Q

stretch reflex: what is it also called?

A

deep tendon reflex

65
Q

stretch reflex: mechanism

A
  1. stretch of muscle activates muscle spindles
  2. Ia from spindle is activated
  3. Ia excites homonymous and synergistic muscles (monosynaptic), as well as excites the inhibitory interneuron which inhibits antagonist muscle (disynaptic)
66
Q

what reflex is described as “reciprocal innervation”

A

stretch reflex

67
Q

decreased or absent reflex, decreased muscle tone indicate what?

A

disease of muscles, neuromuscular junction, sensory neurons, lower motor neurons

68
Q

increased reflex, increased muscle tone indicate what?

A

upper motor neuron lesion

69
Q

role of flexor reflex

A

withdrawal from painful stimulus

70
Q

flexor reflex: mechanism

A
  1. nociceptors activated
    2a. activation of interneurons that excite ipsilateral flexor muscle and inhibit extensor
    2b. activation of interneurons that CROSS spinal cord and excite contralateral extensor muscle and inhibit contralateral flexor muscle (opposite)
71
Q

what reflex is described as “reciprocal inhibition”

A

flexor reflex

72
Q

what reflex is described as “autogenic inhibition”

A

golgi tendon reflex

73
Q

golgi tendon reflex: mechanism

A
  1. muscle contracts and activates Ib afferent in golgi tendon organ
  2. Ib afferent synapses onto Ib inhibitor interneuron
  3. Ib inhibitor interneuron also receives convergent input from skin, joints, and other descending pathways
  4. inhibit original muscle that was stretched
74
Q

golgi tendon reflex: roles (2)

A
  1. signal minute changes in muscle tension to precisely control fine adjustments in muscle contraction in ordinary activities (ex: trying not to crush a delicate object while picking it up)
  2. prevents overly forceful movements and too muscle muscle tension to prevent muscle injury
75
Q

define reciprocal innervation

A

excitations of synergist muscles, inhibition of antagonists

76
Q

define myopathic disease

A

abnormalities in skeletal muscle

77
Q

define neuropathic disease

A

abnormalities in peripheral nerves (sensory or motor)

78
Q

x-linked recessive progressive muscle weakness in boys

A

duchenne’s muscular dystrophy

79
Q

high creatine kinase levels in blood

A

duchenne’s muscular dystrophy

80
Q

waddling, lurching gait with wasting of pelvic girdle muscles

A

duchenne’s muscular dystrophy

81
Q

lack of dystrophin

A

duchenne’s muscular dystrophy

82
Q

dystrophin: function

A

stabilizes membrane of muscle cells

83
Q

duchenne’s muscular dystrophy: patients are more prone to what problems?

A

frequent respiratory infections, pneumonia

84
Q

what is myasthenia gravis?

A

autoimmune condition where antibodies are made against nicotinic acetylcholine receptors in muscle

85
Q

UMN lesion vs. LMN lesion: spasticity

A

UMN

86
Q

UMN lesion vs. LMN lesion: abnormal plantar extension reflex (babinski sign)

A

UMN

87
Q

what is amyotrophic lateral sclerosis (ALS)?

A

progressive degeneration of upper and lower motor neurons

88
Q

what will you see in the thoracic spinal cord of ALS patients?

A

marked pallor of anterior and lateral corticospinal tracts

89
Q

what are normal in ALS patients?

A

eye movements, autonomic nervous system, sensory system

90
Q

guillain barre syndrome: mechanism

A
  1. inflammatory cells and antibodies attack myelin sheath around peripheral nerves
  2. myelin breaks down, axons also become damaged
  3. action potential conduction in motor nerves is slowed or blocked
91
Q

rapid onset of weakness in legs, arms, paresthesia (crawling skin), insensitivity to heat/cold

A

guillain barre

92
Q

rapid onset of muscle weakness 1-2 weeks after a viral infection

A

guillain barre

Block 3 Neuro (4 decks)

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