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NBB Test 1 > Lower Motor Neurons > Flashcards

Lower Motor Neurons Flashcards

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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
We can also control the contraction force of LMNs by
Recruiting additional motor units
26
In the stretch reflex circuit, muscle stretch receptors are connected to la afferents. These stretch receptors are
Excited
27
Then, the Ia afferent makes an excitatory synapse onto quadriceps motor neurons, causing
Muscle Contraction
28
The Ia afferent also makes an excitatory synapse onto an inhibitory interneuron, which inhibits
Hamstring (flexor) motor neurons
29
Provide information about body position/movement
Proprioreceptors
30
Arranged in parallelwith skeletal muscles fibers
Muscle spindles
31
Intrafusal muscle fibers within a connective tissue capsule
Muscle spindles
32
Muscle spindles have 2 types of afferents, both which have a large diameter, are myelinated, and respond to stretch. What are they?
Ia: dynamic (rapid stretch) II: Sustained
33
Innervate muscle spindle intrafusal fibers
γ-motor neurons
34
DO NOT cause skeletal muscle fibers to contract
γ-motor neurons
35
Increase the excitability of the muscle spindle
γ-motor neurons
36
Changes the set point of the stretch feedback loop -Keeps Spindle on-line
Gamma loop
37
The Gamma Loop provides additional control of
Alpha motor neurons and muscle contraction
38
Normally both alpha-and gamma-motor neurons are
Co-activated
39
Increases during skilled movements and motor learning
Gamma activity
40
Used clinically to test motor system
Stretch reflex
41
Indicates pathology to afferents, efferents, or their spinal cord connection
Absent or decreased stretch reflex
42
May indicate pathology above the spinal cord segment. (“supraspinal”) Stretch Reflex used Clinically to test Motor System
Increased reflex
43
The resting tension in a muscle produced by muscle elasticity and resting discharge of motor neurons
Muscle Tone
44
Contributes to postural control and ability to store energy when the muscle is stretched (e.g. during walking or balancing)
Muscle tone
45
Measured by moving around limbs. Flexion-extension, wrist rotation
Muscle tone
46
Occurs when lower motor neurons are damaged
Hypotonia
47
Occurs with supraspinal lesions because stretch reflexes are increased
Hypertonia
48
Proprioceptors in-series with the muscle that respond to muscle TENSION
Golgi-Tendon Organs (GTOs)
49
The stimulus for the flexor withdrawal reflex is
Pain
50
Excitation of flexor motor neurons to entire ipsilateral limb. (removes a limb from a painful stimulus.)
Flexor Withdrawal Reflex
51
Contralateral Limb Extensor muscles are excited in the
Crossed Extension Reflex
52
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
Body-weight supported treadmill training
53
Symptoms of lower motor neuron syndrome will be in the muscles that are innervated by the
LMNs
54
Weakness so severe that a muscle cannot be contracted
Paralysis
55
Weakness or partial paralysis
Paresis
56
Severe weakness or paralysis
Plegia
57
Refers to bilateral lower limb weakness
Diplegia
58
Refers to one side of the body weakness (arm and leg)
Hemiplegia
59
Imprecise term for either weakness or no movement
Palsy
60
Without motor neuron innervation, muscles cannot contract, so lose mass. They also lose trophic support from the motor neurons. This results in
Muscle Atrophy
61
Electromyographic changes: fibrillations, positive sharp waves, fasciculations. These are measures of
Denervation
62
An investigatory tool to assess the source muscle weakness
Electromyography
63
Short-duration, spontaneous biphasic or triphasic potentials produced by single muscle fibers
Fibrillation
64
Only detected with EMG -Indicative of denervated muscle
Fibrillation
65
Larger potentials caused by spontaneous activity in a motor unit or several motor units
Fasciculations
66
Caused by lower motor neuron lesions, particularly in anterior horn cell disease such as ALS
Fasciculations
67
Large fascicultation potentials are suggestive of
Denervation and reinnervation
68
Fasciculations occur with damage to lower motor neurons. Can be normal. These are very common in
ALS
69
Amyotrophic Lateral sclerosis (ALS)àLoss of motor neurons in
Ventral Horn
70
What are 3 things that can cause LMNs?
Guillain-Barre, Post-polio syndrome, Werdnig-Hoffman disease
71
The polio virus attacks ventral horn motor neurons, causing
LMN syndrome
72
The polio recovery and stable period is due to sprouting by neighboring
Motor neurons
73
Occurs years later because those new sprouts cannot be sustained
Post-polio period
74
A group of diseases caused by degeneration of the anterior horns
Spinal Muscle Atrophy (SMA I-IV)
75
Spinal Muscle Atrophy (SMA I-IV) diseases are progressive and begin in infancy. They are due to abnormalities in
Chromosome 5
76
Most common type of SMA (I)
Werdnig-Hoffman Disease
77
Acute infantile spinal muscle atrophy -"Floppy baby" disease
Werdnig-Hoffman Disease
78
What is the inheritance pattern of Werdnig-Hoffman Disease?
Autosomal-recessive inheritance
79
Surface electrodes stimulate skin over the nerve, to excite the nerve. Recording electrodes record the Compound Action Potential
Motor nerve conduction tests
80
Decreased in muscle disease or neuromuscular junction disease
Amplitude of the muscle response (CMAP)
81
Conduction velocity: the time to the CMAP/distance btw. electrodes measures
Fastest fibers
82
Is decreased with demyelinating conditions
Conduction velocity

NBB Test 1 (20 decks)

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