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Chapter 4 The Action Potential

Chapter 4 The Action Potential. Nernst Relation. [ion] out [ion] in. E = 61.54 mV log 10. Goldman Equation. P k [K o ] + P Na [Na o ] P k [K in ] + P Na [Na in ]. V m = 60 log 10. Time Course of Action Potential. Injecting Current into Neuron.

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Chapter 4 The Action Potential

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  1. Chapter 4 The Action Potential

  2. Nernst Relation [ion] out [ion] in E = 61.54 mV log10

  3. Goldman Equation Pk[Ko] + PNa[Nao] Pk[Kin] + PNa[Nain] Vm = 60 log10

  4. Time Course of Action Potential

  5. Injecting Current into Neuron

  6. Frequency vs Depolarization

  7. MembraneCurrents and Conductances

  8. Flipping Potential by Changing Conductance

  9. Sodium Channel Structure

  10. Na Selectivity Filter

  11. Depolarization Changes Configuration

  12. Polarization Opens Na Channel

  13. Question 1 • A new monovalent ion, zirconium, is found to be 100 times more concentrated outside than inside the neural membrane. The neuron has channels that are selectively permeable to zirconium. What is the equilibrium potential for zirconium? • +60 mV, • -60 mV, • +90 mV, • -90 mV, • +120 mV, • -120 mV.

  14. Question 2 • At the normal resting state there is no net current through the membrane. What is the Na/K pump doing? • nothing, • moving ions out, • moving ions in, • moving some ions in and moving others out

  15. Question 3 During the action potential, the sodium current is terminated by the sodium inactivation gate. How is the potassium current terminated? • Potassium inactivation gate b. membrane voltage c. depletion of potassium ions, d. it’s not terminated

  16. Question 4 • When a membrane is “charged” and maintains a voltage across it, most of the ions responsible for the charge are located just adjacent to the membrane. This distribution exists because: • The membrane is sticky for ions, • ions are repelled by the cytoplasm, • ions are attracted to the other side of the membrane, • ions like to accumulate near the ion-selective channels.

  17. Patch Electrode Channel

  18. Channel Openings

  19. Inward Naand Outward KCurrents

  20. Time Course of Action Potential

  21. Propagation

  22. Propagation

  23. Electrotonic Decay

  24. Myelination

  25. Nodes of Ranvier

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