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NBB Test 1 > Lower Motor Neurons > Flashcards

Lower Motor Neurons Flashcards

1
Q

Innervate Muscle

A

Lower (alpha) motor neurons

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2
Q

Have large axon diameters, are heavily myelinated, and are fast-conducting

A

Lower (alpha) motor neurons

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3
Q

Motor neurons end at

A

Neuromuscular Junctions

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4
Q

At the neuromuscular junction, we see acetylcholine nicotine synapse which is called

A

Excitation-contraction coupling

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5
Q

What is an example of a drug that affects the neuromuscular junction?

A

Botulinum Toxin

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6
Q

What is an example of a disease that affects the neuromuscular junction?

A

Myaethenia Gravis

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7
Q

Motor neurons controlling flexor muscles lie dorsal to

A

Motor neurons for extensors

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8
Q

Motor neurons controlling axial muscles lie medial to those controlling

A

Distal muscles

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9
Q

This is an example of

A

Somatotropic arrangement

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10
Q

The arrangement of lower motor neurons in the ventral horn is called

A

Somatotropic arrangement

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11
Q

The ventral horn shape is based on

A

Motor neurons to distal limbs

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12
Q

There are a few lower motor neurons (LMNs) with specific

A

Functions

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13
Q

Lower Motor neurons to trapezius and sternocleidomastoid (accessory nerve)

A

C2: accessory nucleus

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14
Q

Motor neurons to the Phrenic nerve controlling diaphragm

A

C3-C5

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15
Q

Motor neurons innervating urethral and external anal sphincter.

-For voluntary control of urination and defecation

A

S3-S4 Onuf’snucleus

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16
Q

The motor neurons to the pelvic floor muscles

A

S2-S4

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17
Q

Lower motor neurons are components of which CN’s?

A

CNs III-VII and IX-XII

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18
Q

A motor neuron and all the muscle fibers it innervates

A

Motor Unit

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19
Q

All the alpha motor neurons that innervate a single muscle

A

Motor neuron pool

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20
Q

All muscle fibers within a motor unit are the

A

Same type

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21
Q

Determine muscle fiber type

A

Motor neurons

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22
Q

Smaller motor neurons innervate

A

Small fibers

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23
Q

Shows a checkerbord appearance with diffuse blends of fiber types

A

Myosin ATPase stain

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24
Q

Increasing firing rate of alpha motor neurons =

A

Increased force

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25
Q

We can also control the contraction force of LMNs by

A

Recruiting additional motor units

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26
Q

In the stretch reflex circuit, muscle stretch receptors are connected to la afferents. These stretch receptors are

A

Excited

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27
Q

Then, the Ia afferent makes an excitatory synapse onto quadriceps motor neurons, causing

A

Muscle Contraction

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28
Q

The Ia afferent also makes an excitatory synapse onto an inhibitory interneuron, which inhibits

A

Hamstring (flexor) motor neurons

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29
Q

Provide information about body position/movement

A

Proprioreceptors

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30
Q

Arranged in parallelwith skeletal muscles fibers

A

Muscle spindles

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31
Q

Intrafusal muscle fibers within a connective tissue capsule

A

Muscle spindles

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32
Q

Muscle spindles have 2 types of afferents, both which have a large diameter, are myelinated, and respond to stretch. What are they?

A

Ia: dynamic (rapid stretch)
II: Sustained

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33
Q

Innervate muscle spindle intrafusal fibers

A

γ-motor neurons

34
Q

DO NOT cause skeletal muscle fibers to contract

A

γ-motor neurons

35
Q

Increase the excitability of the muscle spindle

A

γ-motor neurons

36
Q

Changes the set point of the stretch feedback loop

-Keeps Spindle on-line

A

Gamma loop

37
Q

The Gamma Loop provides additional control of

A

Alpha motor neurons and muscle contraction

38
Q

Normally both alpha-and gamma-motor neurons are

A

Co-activated

39
Q

Increases during skilled movements and motor learning

A

Gamma activity

40
Q

Used clinically to test motor system

A

Stretch reflex

41
Q

Indicates pathology to afferents, efferents, or their spinal cord connection

A

Absent or decreased stretch reflex

42
Q

May indicate pathology above the spinal cord segment. (“supraspinal”)
Stretch Reflex used Clinically to test Motor System

A

Increased reflex

43
Q

The resting tension in a muscle produced by muscle elasticity and resting discharge of motor neurons

A

Muscle Tone

44
Q

Contributes to postural control and ability to store energy when the muscle is stretched (e.g. during walking or balancing)

A

Muscle tone

45
Q

Measured by moving around limbs. Flexion-extension, wrist rotation

A

Muscle tone

46
Q

Occurs when lower motor neurons are damaged

A

Hypotonia

47
Q

Occurs with supraspinal lesions because stretch reflexes are increased

A

Hypertonia

48
Q

Proprioceptors in-series with the muscle that respond to muscle TENSION

A

Golgi-Tendon Organs (GTOs)

49
Q

The stimulus for the flexor withdrawal reflex is

A

Pain

50
Q

Excitation of flexor motor neurons to entire ipsilateral limb. (removes a limb from a painful stimulus.)

A

Flexor Withdrawal Reflex

51
Q

Contralateral Limb Extensor muscles are excited in the

A

Crossed Extension Reflex

52
Q

Use sensory stimulation (and electrode stimulation) of muscles to activate neural circuits to elicit walking in persons after stroke, spinal cord injury, or with Parkinsons disease

A

Body-weight supported treadmill training

53
Q

Symptoms of lower motor neuron syndrome will be in the muscles that are innervated by the

A

LMNs

54
Q

Weakness so severe that a muscle cannot be contracted

A

Paralysis

55
Q

Weakness or partial paralysis

A

Paresis

56
Q

Severe weakness or paralysis

A

Plegia

57
Q

Refers to bilateral lower limb weakness

A

Diplegia

58
Q

Refers to one side of the body weakness (arm and leg)

A

Hemiplegia

59
Q

Imprecise term for either weakness or no movement

A

Palsy

60
Q

Without motor neuron innervation, muscles cannot contract, so lose mass. They also lose trophic support from the motor neurons. This results in

A

Muscle Atrophy

61
Q

Electromyographic changes: fibrillations, positive sharp waves, fasciculations. These are measures of

A

Denervation

62
Q

An investigatory tool to assess the source muscle weakness

A

Electromyography

63
Q

Short-duration, spontaneous biphasic or triphasic potentials produced by single muscle fibers

A

Fibrillation

64
Q

Only detected with EMG

-Indicative of denervated muscle

A

Fibrillation

65
Q

Larger potentials caused by spontaneous activity in a motor unit or several motor units

A

Fasciculations

66
Q

Caused by lower motor neuron lesions, particularly in anterior horn cell disease such as ALS

A

Fasciculations

67
Q

Large fascicultation potentials are suggestive of

A

Denervation and reinnervation

68
Q

Fasciculations occur with damage to lower motor neurons. Can be normal. These are very common in

A

ALS

69
Q

Amyotrophic Lateral sclerosis (ALS)àLoss of motor neurons in

A

Ventral Horn

70
Q

What are 3 things that can cause LMNs?

A

Guillain-Barre, Post-polio syndrome, Werdnig-Hoffman disease

71
Q

The polio virus attacks ventral horn motor neurons, causing

A

LMN syndrome

72
Q

The polio recovery and stable period is due to sprouting by neighboring

A

Motor neurons

73
Q

Occurs years later because those new sprouts cannot be sustained

A

Post-polio period

74
Q

A group of diseases caused by degeneration of the anterior horns

A

Spinal Muscle Atrophy (SMA I-IV)

75
Q

Spinal Muscle Atrophy (SMA I-IV) diseases are progressive and begin in infancy. They are due to abnormalities in

A

Chromosome 5

76
Q

Most common type of SMA (I)

A

Werdnig-Hoffman Disease

77
Q

Acute infantile spinal muscle atrophy

-“Floppy baby” disease

A

Werdnig-Hoffman Disease

78
Q

What is the inheritance pattern of Werdnig-Hoffman Disease?

A

Autosomal-recessive inheritance

79
Q

Surface electrodes stimulate skin over the nerve, to excite the nerve. Recording electrodes record the Compound Action Potential

A

Motor nerve conduction tests

80
Q

Decreased in muscle disease or neuromuscular junction disease

A

Amplitude of the muscle response (CMAP)

81
Q

Conduction velocity: the time to the CMAP/distance btw. electrodes measures

A

Fastest fibers

82
Q

Is decreased with demyelinating conditions

A

Conduction velocity

NBB Test 1 (20 decks)

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