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NS_BTRAN > Unit3_Motor Systems > Flashcards

Unit3_Motor Systems Flashcards

1
Q

Small motor unit = _____ alpha-motor neuron → innervate small number of muscle fibers → _____ force

A

Small motor unit = Small a-motor neuron → innervate small number of muscle fibers → small force

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2
Q

An alpha-neurons and the muscle fibers that innervates is called?

A

Motor Unit

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3
Q

T/F?

Muscle fibers of a motor unit are of the same fiber type.

A

TRUE

Each muscle fiber is only innervated by one motor NEURON

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4
Q

What size motor unit preferential innervates slow twitch muscle fibers?

A

Small motor unit

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5
Q

What size motor unit requires more input to drive (recruited later and with larger currents)?

A

Large Motor Units

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6
Q

what motor units preferentially innervate fast twitch glycolytic muscle fibers that are quick to fatigue?

A

Large motor units

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7
Q

______________ : population of a-motor neurons that innervate the muscle fibers within a single muscle

A

Motor neuron pool

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8
Q

Describe the size principle for the recruitment of muscles.

A
  • Systemic recruitment of smaller to larger motor units - generates graded forces.
  • Orderly recruitment of increasingly forceful motor units because small neurons have HIGH input resistances → given synaptic current induces larger voltage change in a small motor neuron compared to a large motor neuron
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9
Q

The following describes what type of muscle cells/fibers?

non-spiking muscle fibers, shorten extremely slowly, efficiently generate isometric tension with low fatigability.

A

Tonic

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10
Q

The following describes what type of muscle cells/fibers?

Generate APs to twitch, fatigue very slowly, high conc. of myoglobin and many mitochondria

A

Slow Twitch

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11
Q

The following describes what type of muscle cells/fibers?

activate quickly, many mitochondria, fatigue moderately slowly.

A

Fast Twitch Oxidative

Make up the “Fast Fatigue-Resistant” Motor units.

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12
Q

The following describes what type of muscle cells/fibers?

Actives quickly, fatigue rapidly, few mitochondria, depends on anaerobic glycolysis ATP generation.

A

Fast Twitch Glycolytic

makes up “Fast-Fagtiable” motor units

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13
Q

Exercise/Chronic stimulation can shift motor unit phenotype from fast to slow → slows fatigability, ________ endurance capacity

A

increases

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14
Q

What is muscle tone defined as and why is it important?

A

Muscle tone: defined as resistance to muscle stretch - important for walking, standing, running, etc.

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15
Q

The stretch reflex provided resistance to stretch resulting in what?

A

enhances muscle tone

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16
Q

______________ neuron activation → top-down regulation of muscle tone

A

gamma-motor neuron activation → top-down regulation of muscle tone

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17
Q

__________: condition of decreased muscle tone due to damage to 1a sensory afferents innervating spindles or a-motor neurons innervating muscle

A

Hypotonia

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18
Q

What is Hypotonia?

A

condition of decreased muscle tone d/t damage of 1a sensory afferents innervating spindles or alpha-motor neurons innervating muscles.

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19
Q

__________: due to damage to descending motor pathways that influence spinal cord premotor circuits

A

Hypertonia

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20
Q

What is Hypertonia?

A

d/t damage to descending motor pathways that influences spinal cord pre-motor circuit.

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21
Q

What is a muscle spindle?

A

aka: intrafusal muscle fiber.

proprioceptor embedded within a muscle, composed of muscle fibers.

  • Preferentially signals muscle stretch
  • Important for maintaining muscle tone
  • Feedback system for maintaining muscle strength
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22
Q

What type of fibers do muscle spindles use? (intrafusal muscle fibers)

A

Group 1a and group 2 fibers

23
Q

How do group 1a fibers work?

A

Ia → synapse on a-motor neurons in spinal cord → trigger muscle contraction of homonymous muscle fiber in response to stretch.

  • Have a non-zero firing rate under baseline conditions → maintenance of muscle tone
  • Can signal passive stretch by increasing firing rate and passive shortening by decreasing firing rate
24
Q

______________ : special motor neurons that innervate intrafusal muscle fibers

A

gamma-motor neurons

25
Q

What do alpha and gamma motor neurons do during voluntary contraction?

A

alpha and gamma neurons fire together!

During voluntary contraction, a and y motor neurons fire together → shorten extrafusal AND intrafusal muscle fibers together → maintains spindle sensitivity to stretch

26
Q

Gamma motor neurons do not directly interact with ____ fibers→ not engaged during reflexive contractions

A

1a fibers.

27
Q

Gamma motor neurons do not directly interact with Ia fibers→ not engaged during __________________.

A

reflexive contractions

28
Q

______________: collagen structures at junction of muscle and tendon, made up of capsule and collagen fibrils

A

Golgi tendon organs

29
Q

Golgi tendon organs: ?

A

collagen structures at junction of muscle and tendon, made up of capsule and collagen fibrils.

Important for stabilizing muscle contractions

30
Q

What types of fibers are Golgi tendon organs innervated by?

A

1b fibers

31
Q

how are GTOs connected to muscle and tendons?

A

In series

32
Q

GTOs participate in the _______ ________ _________ of muscle tension.

A

GTOs Participate in negative feedback regulation of muscle tension

33
Q

Are GTOs contractile?

A

NO!!!

GTOs are not innervated by gamma-motor neurons.

34
Q

Hammer tap → stretch muscle spindle→ stimulate Ia sensory axons → activate a-motor neuron in spinal cord → con.tract stretched muscle.

What reflex does this describe?

A

Stretch Reflex Circuit; “Knee-Jerk” reflex

Monosynaptic

35
Q

What is Reciprocal Innervation?

A

1a fibers also innervate other inhibitory interneurons → inhibit other motor neurons → inhibit opposing antagonist muscle

36
Q

In rapid error correction in movements,

Heavier than we expect → muscle spindle stretches more than muscle fibers → increase Ia spindle firing → __________ contraction of muscle fibers via a-motor neurons.

A

increase

37
Q

mismatch between expected and actual muscle stretch detected rapidly and used to correct errors in motor output is called what?

A

Rapid error correction in movements

38
Q

What reflex protects musculature from over exertion by relaxing the synergistic (homonymous) muscle and contracting the antagonist.

A

Extensor-Flexor coupling circuit

39
Q

Ib afferents innervate GTOs → GTOs directly innervate inhibitory and excitatory interneurons in spinal cord is the mechanism for what reflex?

A

Extensor-Flexor coupling circuit

40
Q

Which reflex involves cutaneous sensory/nociceptors receptors that innervate the spinal interneuron motor network?

A

Crossed-Extensor reflex

41
Q

→ coordinate extensor relaxation and flexor contraction on same side as stimulus and converse extensor contraction and flexor relaxation on contralateral side.

Describes what reflex?

A

Crossed-Extensor reflex

42
Q

_____?_____: neural networks that can produce patterned, rhythmic outputs in absence of sensory or central input - coordinate complex movements

A

Central Pattern Generator

43
Q

Where is the Central Pattern Generator (CPG) located?

A

Mesencephalic locomotion center

44
Q

Sensory and descending input from upstream motor centers can modify CPG output, but sensory is ___ necessary for CPGs to generate organized rhythmic motor output

A

NOT necessary

45
Q

What are the modulary functions of the motor system?

A

cardiovascular, respiratory control, and sensorimotor reflexes, eye movement, sleep-wake regulation, and coordination of limb/trunk movement

46
Q

What are the pre-motor functions of the motor system?

A
  • Regulate locomotor speed via Input from mesencephalic locomotor region - initiator of CPG activity.
  • Anticipatory responses to voluntary movement (e.g. flex legs before lifting weight, anticipating change in center of balance).
  • Important for posture, balance and anticipatory movements.
47
Q

__________ tract: send axons ipsilaterally and innervate medial part of ventral horn

A

Reticulospinal tract

48
Q

What is the Vestibular nuclei?

A

vestibular system (vestibulospinal tract) informs brain of head position, orientation, and motion - important for protective responses to falls

49
Q

Sensory info detected by what and sent via 8th cranial nerve to vestibular nuclei

A

semicircular canals

50
Q

Vestibular nuclei sends info via what tract that regulate eye movement?

A

descending projections to cranial nuclei 3, 4, 6.

51
Q

Vestibular nuclei sends info via what tract that regulate head orientation and neck muscle activation?

A

Medial vestibulospinal tracts to medial spinal cord

52
Q

Vestibular nuclei sends info via what tract that control proximal limb musculature.

A

Lateral Vestibulospinal tract to lateral motor pools.

53
Q

What reflex produces eye movement that counter head movements to keep gaze fixed.

A

VOR

no VOR = brain damage

54
Q

The midbrain structure responsible for orienting gaze and body position is called the?

A

Superior colliculus/Tectospinal tract: (aka colliculospinal tract).

Computes a map merging auditory and visual space onto body coordinates.

Descending projections of colliculospinal tract target motor neurons that control axial musculature of neck (e.g. turn head/upper torso towards siren going off)

NS_BTRAN (21 decks)

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