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aNeuro Exam 3- Lindsey's > Motor System > Flashcards

Motor System Flashcards

1
Q

How does graded recruitment of motor neurons work?

A

small neurons have high input resistances (R) –> given current will cause a larger change in these neurons –> will be brought to threshold with less synaptic input than the larger motor neuron

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2
Q

A motor unit is defined as ________.

A

an α motor neuron and the muscle fibers it innervates

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3
Q

Corticospinal axons course through the ______ then gather into the cerebral peduncle on the ventral surface of the midbrain.

A

internal capsule

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4
Q

____ is highly activated during mental rehearsal of movement.

A

The supplementary motor cortex

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5
Q

Activation of α motor neurons ____.

A

maintains muscle tone

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6
Q

What are the 2 general functions of the reticular formation?

A
  1. modulatory functions
  2. premotor functions
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7
Q

During ______, α and ɣ motor neurons fire together, shortening both the extrafusal (normal skeletal muscle) and intrafusal (spindle) muscle fibers together.

A

voluntary contraction

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8
Q

The ______ is responsible for many anticipatory responses to a voluntary movement that help maintain postural control and balance.

A

reticular formation

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9
Q

What is mirror neuron activity?

A

selective neural responses are observed in response to the subject simply watching an action with an intended consequence

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10
Q

Degeneration of ______ is the hallmark of amyotrophic lateral sclerosis (ALS) which is characterized by progressive weakness and wasting of skeletal muscles.

A

α motor neurons

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11
Q

The vestibular nuclei project bilaterally to the _____.

A

abducens nuclei

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12
Q

______ is communicated to the spinal cord through group Ia and group II sensory afferents.

A

Stretch of the muscle spindle

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13
Q

During voluntary contraction, ___ and ____ motor neurons fire together, shortening both the extrafusal (normal skeletal muscle) and intrafusal (spindle) muscle fibers together.

A

α and ɣ

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14
Q

Ia sensory afferents contact ____ motor neurons in the spinal cord, which trigger muscle contraction of the homonymous muscle fiber in response to stretch.

A

α

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15
Q

What is a muscle spindle?

A

a specialized type of sensory receptor, known as a proprioceptor, that is embedded within a muscle and detects muscle stretch

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16
Q

Do intrafusal muscle fibers detect stretch in a contracted or relaxed muscle?

A

both

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17
Q

Descending projections of the ______ tract target motor neurons that control the axial musculature of the neck to generate coordinated orienting responses.

A

colliculospinal (aka tectospinal)

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18
Q

Explain the steps in the knee-jerk reflex.

A

hammer tap stretches the muscle spindles –> 1a sensory axons stimulated –> α motor neurons in the spinal cord activated –> contraction of the stretched muscle

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19
Q

fall –> vestibular system detects downward acceleration –> arms push out and head pulls up

A

the vestibulocervical/vestibulospinal reflex

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20
Q

The _____ informs the brain of head position, orientation, and motion.

A

vestibular system

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21
Q

Stretch of the muscle spindle is communicated to the spinal cord through ______ sensory afferents.

A

group Ia and group II

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22
Q

These are circuits in the spinal cord that contribute to bilateral organized rhythmic behaviors.

A

central pattern generators (CPGs)

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23
Q

1a spindle afferents branch and diverge in the spinal cord to contact large populations of motor neurons which innervate ______ of muscle fibers to create the reflex motion.

A

populations

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24
Q

Slow twitch muscle fibers generate action potentials to twitch, but fatigue very slowly owing to _____.

A

high concentrations of myoglobin and many mitochondria

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25
Q

The vestibular system informs the brain of _____.

A

head position, orientation, and motion

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26
Q

The ______ is a collection of loosely connected areas that lie within the midbrain tegmentum.

A

reticular formation

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27
Q

Explain the crossed extension reflex.

A

cutaneous/nociceptive sensory receptors activated –> spinal interneurons activated –> extensor relaxation with flexor contraction on the same side AND flexor relaxation with extensor contraction on the contralateral side

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28
Q

What are the modulatory functions of the reticular formation?

A
  • cardiovascular control
  • respiratory control
  • some sensorimotor reflexes
  • eye movement coordination
  • sleep wake regulation
  • coordination of limb and trunk movements
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29
Q

______ muscle fibers of the spindle are innervated by a special type of motor neurons called ɣ motor neurons.

A

Intrafusal

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30
Q

Corticospinal axons course through the internal capsule then gather into the ______ on the ventral surface of the midbrain.

A

cerebral peduncle

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31
Q

______ cell bodies reside in the ventral horn of the spinal cord and brainstem cranial motor nuclei.

A

α motor neuron

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32
Q

A _____ is defined as an α motor neuron and the muscle fibers it innervates.

A

motor unit

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33
Q

What is the Golgi tendon organ sensitive to?

A

muscle tension

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34
Q

Tonic muscle fibers are a type of non-spiking muscle fibers that shorten _____ and efficiently generate isometric tension with _____ fatigability.

A

shorten extremely slowly; low fatigue

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35
Q

A small α motor neuron will innervate ______ muscle fibers, forming a motor unit that generates small forces.

A

a small number of

36
Q

1a sensory afferents directly contact _____ motor neurons in the spinal cord.

A

α

37
Q

Give an example of a vestibulocervical/vestibulospinal reflex.

A

fall –> vestibular system detects downward acceleration –> arms push out and head pulls up

38
Q

What are central pattern generators (CPGs)?

A

circuits in the spinal cord that contribute to bilateral organized rhythmic behaviors

39
Q

A given muscle fiber is innervated by how many motor neurons?

A

one

40
Q

α motor neuron cell bodies reside in the _____ of the spinal cord and brainstem cranial motor nuclei.

A

ventral horn

41
Q

The vestibular nuclei project to which cranial nuclei?

A

3 (oculomotor), 4 (trochlear), and 6 (abducens)

42
Q

GTOs are situated _____ with the muscle and tendon, in contrast to the _____ arrangement of the muscle spindles.

A

GTO = in series; muscle spindle = in parallel

43
Q

The knee-jerk reflex is an example of a _____ reflex arc.

A

monosynaptic

44
Q

Fast twitch oxidative muscle fibers activate quickly, have many mitochondria and fatigue ______ because they contain _____ mitochondria.

A

fatigue slowly; lots of mitochondria

45
Q

What does the vestibular ocular reflex (VOR) do?

A

produces eye movements to counter head movements to keep the gaze fixed

46
Q

Degeneration of α motor neurons is the hallmark of _____ which is characterized by progressive weakness and wasting of skeletal muscles.

A

amyotrophic lateral sclerosis (ALS)

47
Q

What activates ɣ motor neurons?

A

descending command axons executing voluntary movements

48
Q

Fast twitch glycolytic fibers activate _____ and fatigue ______ owing to few mitochondria and a dependence of anaerobic glycolysis ATP generation.

A

quickly; rapidly

49
Q

Intrafusal muscle fibers of the spindle are innervated by a special type of motor neurons called ____ motor neurons.

A

ɣ

50
Q

______ muscle fibers activate quickly, have many mitochondria, and fatigue moderately slowly because they contain lots of mitochondria.

A

Fast twitch oxidative

51
Q

Skeletal muscle contraction is driven by _____ neurons that innervate skeletal muscle cells.

A

α motor neurons

52
Q

_____ muscle fibers generate action potentials to twitch, but fatigue very slowly owing to high concentrations of myoglobin and many mitochondria.

A

Slow twitch

53
Q

Stimulation of premotor cortex elicits _____.

A

more complex, compound movements that involve multiple joints

54
Q

What is a muscle spindle made of? Where are they located?

A

a specialized muscle fiber called intrafusal muscle fibers; they run in parallel with the main “extrafusal” muscle fibers

55
Q

What is the size principle?

A

the systematic recruitment of smaller-to-larger motor units

56
Q

_____ muscle fibers are a type of non-spiking muscle fibers that shorten extremely slowly and efficiently generate isometric tension with low fatigability.

A

Tonic

57
Q

Fast twitch oxidative muscle fibers activate _____, have ______ mitochondria and fatigue moderately slowly because they contain lots of mitochondria.

A

activate quickly; many mitochondria

58
Q

cutaneous/nociceptive sensory receptors activated –> spinal interneurons activated –> extensor relaxation with flexor contraction on the same side AND flexor relaxation with extensor contraction on the contralateral side

A

the crossed extension reflex

59
Q

The ______ is critical for orienting gaze and body position.

A

superior colliculus (aka tectum)

60
Q

_____ sensory afferents contact α motor neurons in the spinal cord, which trigger muscle contraction of the homonymous muscle fiber in response to stretch.

A

Ia

61
Q

Fast twitch glycolytic fibers activate quickly and fatigue rapidly owing to ____ mitochondria and a dependence of ______.

A

few; anaerobic glycolysis ATP generation

62
Q

A large α motor neuron will innervate ______ muscle fibers, forming a motor unit that generates large forces.

A

a large number of

63
Q

This is a specialized type of sensory receptor, known as a proprioceptor, that is embedded within a muscle and detects muscle stretch.

A

a muscle spindle

64
Q

The reticular formation is responsible for many anticipatory responses to a voluntary movement that help maintain ______.

A

postural control and balance

65
Q

The superior colliculus (aka tectum) is critical for ______.

A

orienting gaze and body position

66
Q

Ia sensory afferents contact α motor neurons in the spinal cord, which trigger _____.

A

muscle contraction of the homonymous muscle fiber in response to stretch

67
Q

Activation of _____ maintains muscle tone.

A

α motor neurons

68
Q

The population of α motor neurons that innervates the muscle fibers within a single muscle is called the _____ for that muscle.

A

‘motor neuron pool’

69
Q

During voluntary contraction, α and ɣ motor neurons fire together, shortening both the ____ and _____ muscle fibers together.

A

extrafusal (normal skeletal muscle) and intrafusal (spindle)

70
Q

What are the targets of the vestibular nuclei?

A
  1. the medial vestibulospinal tract –> medial spinal cord –> head and neck orientation
  2. lateral vestibulospinal tract –> lateral motor pools –> proximal limb musculature
71
Q

What allows for rapid error-correction in muscle movement and contraction?

A

α and ɣ motor neuron coactivation

72
Q

What is the target of the 8th cranial nerve?

A

the vestibular nuclei

73
Q

Force increases the tension on collagen strands and pinches the intertwined afferent fibers, causing ____.

A

them to fire

74
Q

What is the Golgi tendon organ made of? Where are they found?

A

collagen; at the junction of a muscle and a tendon

75
Q

This produces eye movements to counter head movements to keep the gaze fixed.

A

the vestibular ocular reflex (VOR)

76
Q

This is when selective neural responses are observed in response to the subject simply watching an action with an intended consequence.

A

mirror neuron activity

77
Q

The reticular formation is a collection of loosely connected areas that lie within the _____.

A

midbrain tegmentum

78
Q

1a spindle afferents branch and diverge in the spinal cord to contact ______ of motor neurons which innervate populations of muscle fibers to create the reflex motion.

A

large populations

79
Q

Slow twitch muscle fibers generate action potentials to twitch, but fatigue ____ owing to high concentrations of myoglobin and many mitochondria.

A

very slowly

80
Q

Is motor unit type plastic?

A

yes- exercise and chronic stimulation can shift motor unit phenotype from fast to slow

81
Q

What innervates the Golgi tendon organ?

A

type Ib sensory afferents that wind around and within the collagen strands

82
Q

_______ fibers activate quickly and fatigue rapidly owing to few mitochondria and a dependence of anaerobic glycolysis ATP generation.

A

Fast twitch glycolytic

83
Q

Descending projections of the colliculospinal (aka tectospinal) tract target motor neurons that control the ______ to generate coordinated orienting responses.

A

axial musculature of the neck

84
Q

Gradients from small to large motor units exist, generating _____.

A

graded forces

85
Q

Are small or large motor units recruited first?

A

small- think about grabbing something delicate

aNeuro Exam 3- Lindsey's (20 decks)

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