1. Neural Communication: Action Potential Lesson 10

2. Neural Signaling: Axon n Action Potentials l propagated electrical signal l regenerated n Large & rapid changes in E m l depolarization l repolarization ~

3. Action Potentials n Electrically-gated channels l or voltage-gated n Characteristics l all-or-none l relatively slow l non-decremental ~

4. Threshold of Excitation n also: threshold potential n Triggered at axon hillock l point of decision l integration n Threshold potential l Depolarization; l approximately 10 mV l EPSPs  AP ~

5. -70 -60 0 +40 -80 Time EmEm

6. -70 -60 0 +40 -80 Time Depolarization Na+ influx C & E gradients drive Na+ into cell EmEm

7. Na+ K+ + -

8. Na+ K+ + -

9. -70 -60 0 +40 -80 Time Repolarization K+ efflux EmEm

10. Na+ K+ + -

11. Na+ K+ + -

12. -70 -60 0 +40 -80 Time After- hyperpolarization EmEm

13. Refractory Period n After AP l time-out l prohibits or resists AP l absolute & relative ~

14. Refractory Period n Absolute refractory period l Na+ channels deactivate l will not trigger AP l must reset l one-way transmission of signal n Ball & Chain Model ~

15. Na+ channel deactivation

17. Refractory Period n Relative refractory period l during after-hyperpolarization l requires greater depolarization to reach threshold ~

18. Frequency Code n Intensity of stimulus l frequency of APs l Pattern n Type of stimulus l Brain area that receives signal l Visual, auditory, pain, etc. l Doctrine of Specific Nerve Energies ~

19. FREQUENCY CODE 1.2.3. Weak stimulus Moderate stimulus Strong stimulus

20. Saltatory Conduction n Myelinated neurons l oligodendrocytes & Schwann cells n Long distances transmission l APs relatively slow, regenerates l EPSPs - fast, decremental n Saltatory: combines both types of current l speed without loss of signal ~

21. Saltatory Conduction n Nodes of Ranvier l action potentials l no myelin n Myelinated portions l passive current l decremental but triggers AP at next node ~

22. Saltatory Conduction Nodes of Ranvier

23. PSPs vs APs n Graded l Summation n longer duration l 10-100 msec n chemical-gated n passive spread l instantaneous l decremental n All-or-none n short l 1-2 msec n voltage-gated n propagated l slow l nondecremental