Ch 5 - EDX: Anatomy & Physiology Flashcards

1
Q

Where is the cell body of a motor neuron located?

A

Anterior (ventral) horn of the SC

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2
Q

Where is the cell body of a sensory neuron?

A

Located in dorsal root ganglion outside the SC in intervertebral foramen

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3
Q

What is an axon?

A

Projection from sensory or motor neurons that propagate current flow and transport nutrition

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4
Q

Where do axons of motor neurons project?

A

Projects axons distal

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5
Q

Where do axons of a sensory neuron project?

A

Bipolar cells with 2 axons

1 projects proximal and one distal

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6
Q

What is the innervation ratio?

A

Amount of muscle fibers innervated by one axon

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7
Q

What is the innervation ratio of a muscles of gross movement?

A

High
The higher the ratio the higher the force
ex) 600 muscle fibers to one axon in leg

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8
Q

What is a myotome?

A

Group of muscles innervated by one spinal segement

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9
Q

What is a dermatome?

A

Sensory innervation of one spinal segment

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10
Q

What is a NMJ?

A

Sites where electric impulse along an axon converts to a chemical rxn and translated to an electrical impulse at postsynaptic mem to initiate a muscle fiber action potential (AP)

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11
Q

What is a motor unit?

A
Anterior horn cell
Motor nerve axon
Peripheral nerve
NMJ
Muscle fibers
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12
Q

What is the Henneman size principle?

A

Smaller alpha motor neuron has low threshold for excitation and is recruited first in voluntary contraction

(Large recruited for greater contractile force)

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13
Q

Describe Type I muscle fibers

A

Small cell body
Thin diameter axon
Low innervation ratio
Slow twitch muscle fibers

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14
Q

Describe Type II muscle fibers

A

Large cell body
Thick diameter axon
High innervation ratio
Fast twitch muscle fibers

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15
Q

What type of fibers does EDX evaluate?

A

Ia (large, myelinated) fibers

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16
Q

What does the cathode of EDX do?

A

Neg cathode attracts positive charges and lowers membrane potential allowing Na to rush through voltage-gated channels and generate an AP

17
Q

How do cooler temperatures impact EDX?

A

Prolongs latency
Inc: amp, duration, phases
Dec: CV

18
Q

What is saltatory conduction?

A

Propogation of current between myelin in Na channels in nodes of Ranvier

19
Q

What is orthodromic recording?

A

AP recorded in direction of physiologic conduction

20
Q

What is antidromic recording?

A

AP recorded in opposite direction of physiologic conduction

21
Q

How is a miniature endplate potential (MEPP) created?

A

Spontaneous release of Ach ~ 5 sec during resting state at NMJ

22
Q

How is an endplate potential (EPP) produced?

A

Nerve depolarization opens voltage-gated Ca channels and release Ach into synaptic cleft which inc # of MEPP and generates a MUAP

23
Q

Describe a Type I muscle fiber

A
Slow Twitch Oxidative
Small
Dark
Early recruitment
Highly resistant to fatigue
Mild effort (4-8 hz)
Slow, prolonged firing freq
Fine, precise movements
Small innervation ratio
Small amp/duration
Aerobic
24
Q

Describe a Type IIA muscle fiber

A
Fast Twitch Oxidative-Glycolytic
Large
Dark
Late recruitment
Fatigue resistant
Intermed effort (20-30 Hz)
Fast, unsustained firing freq
Gross movements
Large innervation ratio
Large amp/duration
Anaerobic
25
Q

What is Endoneurium?

A

CT surrounding each individual axon and its myelin sheath

26
Q

What is Perineurium?

A

CT surrounding bundles or fascicles of myelinated and unmyelinated nerve fibers

27
Q

What is Epineurium?

A

Loose CT surrounding entire nerve that holds fascicles together and protects from compression

28
Q

What does the needle EMG monitor?

A

Factors related to the motor unit and thus the alpha motor neuron

29
Q

Describe a Type IIB muscle fiber

A
Fast Twitch Glycolytic
Large
Pale
Late recruitment
Fatigue sensitive
High effort (20-30 Hz)
Fast, unsustained firing freq
Gross movements
Large innervation ratio
Large amp/duration
Anaerobic