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Cable Model Voltage Clamp Propagation of an Action Potential

Cable Model Voltage Clamp Propagation of an Action Potential. Illustrations are taken from: J. Malmivuo, R. Plonsey, Bioelectromagnetism, Oxford Press, 1995 http://butler.cc.tut.fi/~malmivuo/bem/book/. Cable Model of Axon. Steady-State Response. Propagation of Activation.

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Cable Model Voltage Clamp Propagation of an Action Potential

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  1. Cable ModelVoltage ClampPropagation of an Action Potential Illustrations are taken from: J. Malmivuo, R. Plonsey, Bioelectromagnetism, Oxford Press, 1995 http://butler.cc.tut.fi/~malmivuo/bem/book/ EE-515 Bioelectricity & Biomagnetism 2002 Fall Murat Eyuboglu

  2. Cable Model of Axon EE-515 Bioelectricity & Biomagnetism 2002 Fall Murat Eyuboglu

  3. EE-515 Bioelectricity & Biomagnetism 2002 Fall Murat Eyuboglu

  4. Steady-State Response EE-515 Bioelectricity & Biomagnetism 2002 Fall Murat Eyuboglu

  5. Propagation of Activation EE-515 Bioelectricity & Biomagnetism 2002 Fall Murat Eyuboglu

  6. Uniform Current Injection EE-515 Bioelectricity & Biomagnetism 2002 Fall Murat Eyuboglu

  7. Step Excitation EE-515 Bioelectricity & Biomagnetism 2002 Fall Murat Eyuboglu

  8. Voltage Clamp Experiment EE-515 Bioelectricity & Biomagnetism 2002 Fall Murat Eyuboglu

  9. Membrane Current EE-515 Bioelectricity & Biomagnetism 2002 Fall Murat Eyuboglu

  10. Membrane Current EE-515 Bioelectricity & Biomagnetism 2002 Fall Murat Eyuboglu

  11. Ionic Membrane Currents EE-515 Bioelectricity & Biomagnetism 2002 Fall Murat Eyuboglu

  12. Selective measurement of sodium and potassium currents by selective blocking of Na and K channels Control measurement without pharmacological agents. After tetrodotoxin (TTX). After tetraethylammonium (TEA). EE-515 Bioelectricity & Biomagnetism 2002 Fall Murat Eyuboglu

  13. EE-515 Bioelectricity & Biomagnetism 2002 Fall Murat Eyuboglu

  14. Potassium Conductance EE-515 Bioelectricity & Biomagnetism 2002 Fall Murat Eyuboglu

  15. Rate Constants & noo EE-515 Bioelectricity & Biomagnetism 2002 Fall Murat Eyuboglu

  16. The potassium ions cross the membrane only through channels that are specific for potassium. Hodgkin and Huxley supposed that the opening and closing of these channels are controlled by electrically charged particles called n-particles. These may stay in a permissive (i.e., open) position (for instance inside the membrane) or in a nonpermissive (i.e., closed) position (for instance outside the membrane), and they move between these states (or positions) with first-order kinetics. The probability of an n-particle being in the open position is described by the parameter n, and in the closed position by (1 - n), where 0 n 1. Thus, when the membrane potential is changed, the changing distribution of the n-particles is described by the probability of n relaxing exponentially toward a new value. EE-515 Bioelectricity & Biomagnetism 2002 Fall Murat Eyuboglu

  17. The process determining the variation of K conductance with depolarization and repolarization EE-515 Bioelectricity & Biomagnetism 2002 Fall Murat Eyuboglu

  18. Sodium Conductance EE-515 Bioelectricity & Biomagnetism 2002 Fall Murat Eyuboglu

  19. Rate Constants for Na EE-515 Bioelectricity & Biomagnetism 2002 Fall Murat Eyuboglu

  20. EE-515 Bioelectricity & Biomagnetism 2002 Fall Murat Eyuboglu

  21. EE-515 Bioelectricity & Biomagnetism 2002 Fall Murat Eyuboglu

  22. The behavior of sodium conductance is initially similar to that of potassium conductance, except that the speed of the conductance increase during depolarization is about 10 times faster. The rise in sodium conductance occurs well before the rise in potassium conductance becomes appreciable. Hodgkin and Huxley assumed again that at the sodium channels certain electrically charged particles called m-particles exist whose position control the opening of the channel. Thus they have two states, open (permissive) and closed (nonpermissive); the proportion m expresses the fraction of these particles in the open state (for instance inside the membrane) and (1 - m) the fraction in the closed state (for instance outside the membrane), where 0 m 1. EE-515 Bioelectricity & Biomagnetism 2002 Fall Murat Eyuboglu

  23. The process determining the variation of K conductance with depolarization and repolarization EE-515 Bioelectricity & Biomagnetism 2002 Fall Murat Eyuboglu

  24. Voltages in the Squid Axon EE-515 Bioelectricity & Biomagnetism 2002 Fall Murat Eyuboglu

  25. In addition to the variables discussed above, the constants of the Hodgkin-Huxley model are as shown: Cm = 1 µF/cm² Vr - VNa = -115 mV Vr - VK = +12 mV Vr - VL = -10.613 mV GNa max = 120 mS/cm² GK max = 36 mS/cm² GL = 0.3 mS/cm² EE-515 Bioelectricity & Biomagnetism 2002 Fall Murat Eyuboglu

  26. H-H Model for Propagation EE-515 Bioelectricity & Biomagnetism 2002 Fall Murat Eyuboglu

  27. During a Propagating Nerve Impulse EE-515 Bioelectricity & Biomagnetism 2002 Fall Murat Eyuboglu

  28. Propagating Nerve Impulse EE-515 Bioelectricity & Biomagnetism 2002 Fall Murat Eyuboglu

  29. End of the Lecture EE-515 Bioelectricity & Biomagnetism 2002 Fall Murat Eyuboglu

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