electrphysilogy action potential
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Transcript electrphysilogy action potential
Basic Electrophysiology for
Electrotherapy
Nan-Ying Yu
Mar.4.2008
Textbook: Robinson, Andrew J., & Snyder-Mackler, Lynn,
Clinical electrophysiology: electrotherapy and electrophysiologic
testing, Williams & Wilkins, pp.83-119, 1995.
Electrical Excitability of Muscle and
Nerve
Resting membrane potential
-90 mV for muscle fibers
-75 mV for peripheral nerve fibers
Action potentials (depolarization/
repolarization/ hyperpolarization)
“all or none” in character
2
Action Potential Propagation
Two most important passive electrical properties
with respect to the transmission of ion currents
in 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
speed
3
Experiment Setup for Examining
AP Propagation
4
Orthodromic v.s. Antidromic Propagation
(Physiologic)
5
Classification of Peripheral Nerve
6
Factors influencing muscle force
production
Frequency of Activation
Number of Fibers Activated
7
Frequency of Activation
v.s.
Number of Fibers Activated
8
Control of Force Generation in
Volitional Contraction
“size principle” (recruitment)
S FR FF
“rate coding” (discharge frequency)
9
Volitional Contraction
10
Activation of excitable tissues with
electrical stimulation
11
Stimulus characteristics for activation
of excitable tissues
strength-duration curve
rheobase
chronaxie
12
S-D curves
13
Diagrammatic representation for the result
of S-D curves in different excitable tissues
14
Clinical responses to nerve and
muscle stimulation
Sensory-Level Stimulation
Motor-Level Stimulation
Noxious-Level Stimulation
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Clinical responses to nerve and
muscle stimulation
16
Sensory-Level Stimulation
Frequency set 1 to 5 pps “Tapping”
sensation
Frequency >15 gradual diminution in
the ability to sense the stimulation
(adaptation)
17
Motor-Level Stimulation
Compared to volitional recruitment, recruitment order in ES tends to
be reversed.
18