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Physiology > Intro to Motor system > Flashcards

Intro to Motor system Flashcards

1
Q

What type of movement is walking, chewing etc?

A

Rhythmic motor pattern (subconscious usually)

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2
Q

What does the nervous system need to know in order to produce movement? (4)

A
  1. Initial length of the muscle
  2. Velocity of muscle length change
  3. External loads acting to oppose movement
  4. Visual and vestibular info
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3
Q

What type of fibers innervate GTOs?

A

Type Ib afferent

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4
Q

What type of fibers innervate muscle spindles?

A

Type Ia afferent

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5
Q

What is feedback control?

A

use of sensory information during movement to make corrections to the on-going movement.

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6
Q

What is feedforward control?

A
  • Sensory information contributes to anticipating the effect of planed movement
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7
Q

What is the motor pathway?

A

Parietal/premotor/supplementary motor cortex to the

Primary motor cortex
Brainstem
Spinal cord

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8
Q

What are the two inputs to the thalamus that affect its output to the primary motor cortex?

A

Basal nuclei

Cerebellum

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9
Q

What are the two places that the cerebellum sends information to in the motor pathway?

A

Brainstem

Thalamus

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10
Q

What is the hierarchical organization of the motor control centers?

A

Cortical areas
Brainstem
Spinal cord

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11
Q

What two parts of the brain modify output from the motor cortex?

A

Basal ganglia

Cerebellum

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12
Q

What is the difference between UMNs and LMNs?

A

UMNs go to a ganglia/nucleus

LMNs symapse on effector muscle

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13
Q

What role do gamma motor neurons play in the nervous system?

A

Innervate intrafusal skeletal muscle fibers, the small muscle fibers within the muscle spindles

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14
Q

What are skeltal-fusimotor neurons?

A

Nerves that innervate both extrafusal and intrafusal muscle fibers: this is sometimes called beta activation

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15
Q

Where are LMNs found in the spinal cord?

A

Anterior horn of the gray matter, with their axons leaving the spinal cord via the ventral root

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16
Q

What are alpha motor neurons?

A

neurons that innervate muscles in the PNS

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17
Q

What is a motor neuron pool?

A

All the neurons that control one muscle

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18
Q

What is a motor unit?

A

one alpha motor neuron plus all the skeletal muscle fibers it innervates

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19
Q

What are the four functional components of a motor unit?

A
  • cell body of motor neuron
  • axon
  • neuromuscular junction
  • muscle fibers
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20
Q

Where are small motor units used in the body?

A

Where fine control is needed (oculomotor muscles in the eyes)

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21
Q

Where are large motor units used in the body?

A

In strong muscles that do not need fine control

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22
Q

What is the pathogenesis of post-polio syndrome?

A

surviving motor neurons “adopt orphaned” muscle fibers. This increases stress on these fibers, with repeated remodeling with denervation and reinnervation

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23
Q

What produces graded muscle contraction? (there are two options here)

A

recruitment of more and more muscle units and/or increase the rate at which the alpha motor neuron of each motor unit is firing.

24
Q

What is Henneman’s size principle?

A

order of recruitment of motor neurons = first recruit small neurons, and then larger neurons, since smaller ones will depolarize first

25
Q

True or false: muscles need constant, low level stimulation. Why?

A

True, since need muscle protein gene expression

26
Q

What are the symptoms of a LMN lesion?

A

Atrophy
Hypotonia
Hyporeflexia
Fibrillations/fasciculations

27
Q

What causes the weak reflexes seen in a LMN damage?

A

Loss of alpha motor neurons to the muscle

28
Q

What are fasciculations?

A
  • visible twitches of muscle that can be seen as ripples under the skin
29
Q

What are fibrillations?

A

spontaneous activity within single muscle fibers. They are not visible clinically since they are too small to be seen as movement through the skin

30
Q

How do you detect fibrillations of muscle?

A

Electromyography

31
Q

Fasciculations are a sign of what?

A

LMN disorder

32
Q

What is the difference in innervation between fasciculations and fibrillations?

A

Fasciculations are when entire muscle groups are still connected after a lesion, so contract together.

Fibrillations are when fibers are not innervated together, thus single fibers twitch

33
Q

What is an injury potential?

A

Potential generated at site of injury to a motor neuron axon.

34
Q

What happens to muscles that are denervated that causes them to be super sensitive?

A

Increased number of Ach receptors

35
Q

Flaccid paralysis results when what occurs with the nerves?

A

Total loss of innervation

36
Q

What is paresis?

A

paresis refers to partial loss of voluntary contraction or voluntary muscle weakness.

37
Q

Which type of lesion causes flaccid paralysis? Spastic?

A 
Flaccid = LMN or initially with UMN
Spastic = UMN
38
Q

A complete transection of the spinal cord will result in flaccid or spastic paralysis?

A

Initially flaccid, then spastic

39
Q

What is spinal shock?

A

the temporary loss of spinal cord reflex activity that occurs below a total (or near total) spinal cord injury.

40
Q

What are the three components/symptoms of spinal shock?

A
  1. Flaccid paralysis
  2. Areflexia
  3. Loss of autonomic function below level of transection
41
Q

How long do symptoms of spinal shock last? What then?

A

a few days to weeks

Progresses to hyperreflexia

42
Q

Babinski sign it a test for what type of neuron lesion?

A

UMN

43
Q

What is the MOA of spinal shock syndrome? (3)

A

Increased blood supply or loss of edema around spinal cord

Loss of inhibition of gamma motor neurons

44
Q

What is an UMN?

A

a neuron in a higher motor area (e.g. motor cortex, premotor cortex, brainstem center) that synapses on a lower motor neuron or on an interneuron which synapses on a lower motor neuron.

45
Q

Spinal cord lesions (e.g. those caused by a broken neck) damage what type of neurons?

A

LMNs at the site of injury

UMN if spinal tract involved

46
Q

What are the two parts of the spinal cord that produce a multitude of symptoms if transected?

A

The cervical and lumbar enlargements

47
Q

What is spasticity?

A

a motor disorder characterized by a velocity- dependent increase in tonic stretch reflexes (muscle tone) with exaggerated tendon jerks, resulting from hyperexcitability of the stretch reflex, and is one component of the upper motor neuron syndrome.

48
Q

The oculomotor and trochlear nuclei are UMN or LMNs?

A

LMNs

49
Q

True or false: there can be LMNs above UMNs in the spinal cord

A

True, as long as they are not part of the same tract

50
Q

True or false:Damage of the spinal cord can damage both LMNs and UMNs

A

True

51
Q

True or false: spinal cord lesions always affect all of the descending motor tracts

A

False–can have only one

52
Q

Upper motor neuron syndrome is what?

A

When all tracts of UMNs are lesioned

53
Q

DTR are overactive in UMN or LMN lesions?

A

UMN

54
Q

If a pt presents with both UMN and LMN signs, what should immediately be in your ddx?

A

ALS

55
Q

What is the pathogenesis of ALS?

A

Loss of myelination of UMNs and LMN of unknown etiology

Physiology (75 decks)

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