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Membrane Potentials and Action Potentials

Membrane Potentials and Action Potentials. Guyton 2011 Chapter 5. Membrane Potentials and Action Potentials. Resting Membrane Potential. Membrane Potentials and Action Potentials. Membrane potentials caused by ion diffusion. Na. Ca. -90 mv. Cl. Electrical Gradient. Chemical Gradient.

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Membrane Potentials and Action Potentials

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  1. Membrane Potentials and Action Potentials Guyton 2011 Chapter 5

  2. Membrane Potentials and Action Potentials Resting Membrane Potential

  3. Membrane Potentials and Action Potentials Membrane potentials caused by ion diffusion Na Ca -90 mv Cl Electrical Gradient Chemical Gradient K

  4. Membrane Potentials and Action Potentials Nernst Equation Electrical Force Chemical Force

  5. Membrane Potentials and Action Potentials Goldman – Hodgkin - Katz Equation

  6. Membrane Potentials and Action Potentials Origin of the normal resting membrane potential

  7. Membrane Potentials and Action Potentials

  8. Membrane Potentials and Action Potentials Voltage-Gated Channels

  9. Membrane Potentials and Action Potentials Point 1 Tetrodotoxin (TTX) blocks sodium channels Tetraethylammonium blocks potassium channels

  10. Membrane Potentials and Action Potentials • Point 2 Local (subthreshold ) potential All – or – nothing principle Safety Factor

  11. Membrane Potentials and Action Potentials Nerve Trunks

  12. Membrane Potentials and Action Potentials Propagation of action potential In unmyelinated nerves

  13. Membrane Potentials and Action Potentials Propagation of action potential In myelinated nerves • Saltatory conduction in myelinated fibers • Increases velocity 5-50 fold • Conserve energy • The velocity of action potential conduction in nerve fibers varies from as little as 0.25 m/sec in small unmyelinated fibers to as great as 100 m/sec in large myelinated fibers

  14. Membrane Potentials and Action Potentials Re-establishing Ionic Gradients by Na-K Pump • Point 3 Indeed, 100,000 to 50 million impulses can be transmitted by Large nerve fibers before the concentration differences reach the point that action potential conduction cease

  15. Membrane Potentials and Action Potentials Heat production as a result of the increased Na-K pump activity • Point 4 The pumping activity increases approximately in proportion to the third power of this intracellular sodium concentration

  16. Membrane Potentials and Action Potentials • Point 5 Plateau in Some Action Potentials

  17. Membrane Potentials and Action Potentials • Point 3 Repetitive discharge

  18. Membrane Potentials and Action Potentials Refractory periods

  19. Membrane Potentials and Action Potentials • High extracellular Calcium • Stabilizers and Local Anesthetics • Procaine and Tetracaine

  20. The End

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