electrphysilogy action potential
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Basic Electrophysiology forElectrotherapy
Nan-Ying YuMar.4.2008
Textbook: Robinson, Andrew J., & Snyder-Mackler, Lynn,
Clinical electrophysiology: electrotherapy and electrophysiologic
testing, Williams & Wilkins, pp.83-119, 1995.
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Electrical Excitability of Muscle andNerve
Resting membrane potential
-90 mV for muscle fibers
-75 mV for peripheral nerve fibers
Action potentials (depolarization/
repolarization/ hyperpolarization)
all or none in character
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Action Potential Propagation
Two most important passive electrical properties
with respect to the transmission of ion currentsin nerve and muscles are the membrane
resistance (rm) and the internal (intracellular)
resistance (ri)
Small-diameter fibers have relative high internal
resistance as compared to large-diameter fibers
The higher the ri the slower the propagation
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Experiment Setup for ExaminingAP Propagation
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Orthodromic v.s. Antidromic Propagation(Physiologic)
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Classification of Peripheral Nerve
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Factors influencing muscle forceproduction
Frequency of Activation Number ofFibers Activated
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Frequency ofActivation
v.s.Number ofFibers Activated
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Control ofForce Generation inVolitional Contraction
size principle (recruitment)
S FR FF
rate coding (discharge frequency)
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Volitional Contraction
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Activation of excitable tissues withelectrical stimulation
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Stimulus characteristics for activationof excitable tissues
strength-duration curve
rheobase
chronaxie
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S-D curves
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Diagrammatic representation for the resultof S-D curves in different excitable tissues
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Clinical responses to nerve andmuscle stimulation
Sensory-Level Stimulation
Motor-Level Stimulation
Noxious-Level Stimulation
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Clinical responses to nerve andmuscle stimulation
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Sensory-Level Stimulation
Frequency set 1 to 5 pps Tapping
sensation
Frequency >15 gradual diminution in
the ability to sense the stimulation
(adaptation)
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Motor-Level Stimulation
Compared to volitional recruitment, recruitment order in ES tends to
be reversed.
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