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Basic Electrophysiology for Electrotherapy

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.

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Basic Electrophysiology for Electrotherapy

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  1. 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.

  2. 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

  3. 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

  4. Experiment Setup for Examining AP Propagation 4

  5. Orthodromic v.s. Antidromic Propagation(Physiologic) 5

  6. Classification of Peripheral Nerve 6

  7. Factors influencing muscle force production • Number of Fibers Activated • Frequency of Activation 7

  8. Frequency of Activationv.s. Number of Fibers Activated 8

  9. Control of Force Generation in Volitional Contraction • “size principle” (recruitment) S  FR  FF • “rate coding” (discharge frequency) 9

  10. Volitional Contraction 10

  11. Activation of excitable tissues with electrical stimulation 11

  12. Stimulus characteristics for activation of excitable tissues strength-duration curve rheobase chronaxie 12

  13. S-D curves 13

  14. Diagrammatic representation for the result of S-D curves in different excitable tissues 14

  15. Clinical responses to nerve and muscle stimulation • Sensory-Level Stimulation • Motor-Level Stimulation • Noxious-Level Stimulation 15

  16. Clinical responses to nerve and muscle stimulation 16

  17. Sensory-Level Stimulation • Frequency set 1 to 5 pps  “Tapping” sensation • Frequency >15  gradual diminution in the ability to sense the stimulation (adaptation) 17

  18. Motor-Level Stimulation • Compared to volitional recruitment, recruitment order in ES tends to be reversed. 18

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