1. Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Fundamentals of Anatomy & Physiology SIXTH EDITION Chapter 12, part 2 Neural tissue

2. Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings SECTION 12-4 Neurophysiology: Ions and Electrical Signals

3. Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Electrochemical gradient Sum of all chemical and electrical forces acting across the cell membrane Sodium-potassium exchange pump stabilizes resting potential at ~70 mV The transmembrane potential

4. Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Figure 12.11 Figure 12.11 An Introduction to the Resting Potential

5. Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Figure 12.12 Electrochemical Gradients Figure 12.12

6. Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Membrane contains Passive (leak) channels that are always open Active (gated) channels that open and close in response to stimuli Changes in the transmembrane potential

7. Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Figure 12.13 Gated Channels Figure 12.13

8. Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Chemically regulated channels Voltage-regulated channels Mechanically regulated channels Three types of active channels

9. Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings A change in potential that decreases with distance Localized depolarization or hyperpolarization Graded potential

10. Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Figure 12.14 Graded Potentials Figure 12.14.1

11. Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Figure 12.14 Graded Potentials Figure 12.14.2

12. Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Figure 12.15 Figure 12.15 Depolarization and Hyperpolarization

13. Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Appears when region of excitable membrane depolarizes to threshold Steps involved Membrane depolarization and sodium channel activation Sodium channel inactivation Potassium channel activation Return to normal permeability Action Potential

14. Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Figure 12.16.1 Figure 12.16 The Generation of an Action Potential

15. Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Figure 12.16.2 Figure 12.16 The Generation of an Action Potential

16. Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Generation of action potential follows all- or-none principle Refractory period lasts from time action potential begins until normal resting potential returns Continuous propagation spread of action potential across entire membrane in series of small steps salutatory propagation action potential spreads from node to node, skipping internodal membrane Characteristics of action potentials

17. Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Figure 12.17 Figure 12.17 Propagation of an Action Potential along an Unmyelinated Axon

18. Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Figure 12.18.1 Figure 12.18 Saltatory Propagation along a Myelinated Axon

19. Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Figure 12.18.2 Figure 12.18 Saltatory Propagation along a Myelinated Axon

20. Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Type A fibers Type B fibers Type C fibers Based on diameter, myelination and propagation speed Axon classification

21. Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Muscle tissue has higher resting potential Muscle tissue action potentials are longer lasting Muscle tissue has slower propagation of action potentials Animation: The action potential PLAY Muscle action potential versus neural action potential