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Neural Communication Action Potential Lecture  11
Postsynaptic Potentials <ul><li>EPSP </li></ul><ul><ul><li>Excitatory </li></ul></ul><ul><ul><li>Depolarization </li></ul>...
Action Potentials <ul><li>Large and rapid change in membrane potential </li></ul><ul><li>electrically-gated channels  </li...
AP Characteristics <ul><li>Voltage-gated channels </li></ul><ul><li>All or none </li></ul><ul><li>Slow </li></ul><ul><li>N...
V m -70 -60 0 +40 -80 Time
V m -70 -60 0 +40 -80 Time
-70 -60 0 +40 -80 Time   Depolarization Na+ influx C & E gradients drive Na+ into cell V m
-70 -60 0 +40 -80 Time   Repolarization K+ efflux V m
-70 -60 0 +40 -80 Time   V m After-  hyperpolarization
Refractory Period <ul><li>after AP </li></ul><ul><ul><li>won’t fire again </li></ul></ul><ul><ul><li>relative & absolute <...
Relative Refractory Period V m -70 -60 0 +40 -80 Time
Absolute refractory period <ul><li>Na+ channels deactivate </li></ul><ul><ul><li>will not trigger AP </li></ul></ul><ul><u...
Na+ channel deactivation
Na+ channel deactivation
Frequency Code <ul><li>Pattern = Intensity of stimulus </li></ul><ul><ul><li>frequency of APs  </li></ul></ul><ul><li>Plac...
FREQUENCY CODE Weak stimulus Moderate stimulus Strong stimulus 1. 2. 3.
Subthreshold stimulus Moderate stimulus Strong stimulus Injected  Current -65 mV 0 mV Time  
Saltatory Conduction <ul><li>Myelinated neurons </li></ul><ul><ul><li>oligodendroglia & Schwann cells </li></ul></ul><ul><...
Saltatory Conduction <ul><li>Nodes of Ranvier  </li></ul><ul><ul><li>action potentials </li></ul></ul><ul><li>Myelinated  ...
Saltatory Conduction Nodes of Ranvier
PSPs  vs  APs <ul><li>Graded </li></ul><ul><ul><li>Summation </li></ul></ul><ul><li>longer duration </li></ul><ul><ul><li>...
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~BN11 action potential.ppt

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~BN11 action potential.ppt

  1. 1. Neural Communication Action Potential Lecture 11
  2. 2. Postsynaptic Potentials <ul><li>EPSP </li></ul><ul><ul><li>Excitatory </li></ul></ul><ul><ul><li>Depolarization </li></ul></ul><ul><ul><li>Na+ influx </li></ul></ul><ul><ul><li>AP more likely </li></ul></ul><ul><li>IPSP </li></ul><ul><ul><li>Inhibitory </li></ul></ul><ul><ul><li>Hyperpolarization </li></ul></ul><ul><ul><li>K+ efflux </li></ul></ul><ul><ul><li>AP less likely </li></ul></ul><ul><li>Soma & Dendrites </li></ul><ul><li>Chemically-gated channels </li></ul><ul><li>Passive current </li></ul><ul><li>Graded </li></ul><ul><li>Summation </li></ul>
  3. 3. Action Potentials <ul><li>Large and rapid change in membrane potential </li></ul><ul><li>electrically-gated channels </li></ul><ul><li>EPSPs </li></ul><ul><ul><li>threshold potential </li></ul></ul><ul><li>Occurs in axon </li></ul><ul><ul><li>triggered at axon hillock ~ </li></ul></ul>
  4. 4. AP Characteristics <ul><li>Voltage-gated channels </li></ul><ul><li>All or none </li></ul><ul><li>Slow </li></ul><ul><li>Non-decremental </li></ul><ul><li>Self Propagated </li></ul><ul><ul><li>regenerated ~ </li></ul></ul>
  5. 5. V m -70 -60 0 +40 -80 Time
  6. 6. V m -70 -60 0 +40 -80 Time
  7. 7. -70 -60 0 +40 -80 Time Depolarization Na+ influx C & E gradients drive Na+ into cell V m
  8. 8. -70 -60 0 +40 -80 Time Repolarization K+ efflux V m
  9. 9. -70 -60 0 +40 -80 Time V m After- hyperpolarization
  10. 10. Refractory Period <ul><li>after AP </li></ul><ul><ul><li>won’t fire again </li></ul></ul><ul><ul><li>relative & absolute </li></ul></ul><ul><li>Relative </li></ul><ul><ul><li>during after hyperpolarization </li></ul></ul><ul><ul><li>requires greater depolarization ~ </li></ul></ul>
  11. 11. Relative Refractory Period V m -70 -60 0 +40 -80 Time
  12. 12. Absolute refractory period <ul><li>Na+ channels deactivate </li></ul><ul><ul><li>will not trigger AP </li></ul></ul><ul><ul><li>must reset </li></ul></ul><ul><li>Ball & Chain Model ~ </li></ul>
  13. 13. Na+ channel deactivation
  14. 14. Na+ channel deactivation
  15. 15. Frequency Code <ul><li>Pattern = Intensity of stimulus </li></ul><ul><ul><li>frequency of APs </li></ul></ul><ul><li>Place = type of stimulus </li></ul><ul><ul><li>Visual, auditory, pain, etc. </li></ul></ul><ul><ul><li>Brain area that receives signal </li></ul></ul><ul><ul><li>Doctrine of Specific Nerve Energies ~ </li></ul></ul>
  16. 16. FREQUENCY CODE Weak stimulus Moderate stimulus Strong stimulus 1. 2. 3.
  17. 17. Subthreshold stimulus Moderate stimulus Strong stimulus Injected Current -65 mV 0 mV Time 
  18. 18. Saltatory Conduction <ul><li>Myelinated neurons </li></ul><ul><ul><li>oligodendroglia & Schwann cells </li></ul></ul><ul><li>Transmit long distances </li></ul><ul><ul><li>APs relatively slow, regenerates </li></ul></ul><ul><ul><li>EPSPs - fast, decremental </li></ul></ul><ul><li>Saltatory: combines both types of current </li></ul><ul><ul><li>speed without loss of signal ~ </li></ul></ul>
  19. 19. Saltatory Conduction <ul><li>Nodes of Ranvier </li></ul><ul><ul><li>action potentials </li></ul></ul><ul><li>Myelinated </li></ul><ul><ul><li>like electricity through wire </li></ul></ul><ul><ul><li>decremental but triggers AP at next node </li></ul></ul><ul><li>Safety factor - trigger AP across 5 nodes </li></ul><ul><ul><li>.2 - 2 mm apart </li></ul></ul><ul><ul><ul><li>larger neurons  farther apart ~ </li></ul></ul></ul>
  20. 20. Saltatory Conduction Nodes of Ranvier
  21. 21. PSPs vs APs <ul><li>Graded </li></ul><ul><ul><li>Summation </li></ul></ul><ul><li>longer duration </li></ul><ul><ul><li>*10-100 msec </li></ul></ul><ul><li>chemical-gated </li></ul><ul><li>passive spread </li></ul><ul><ul><li>instantaneous </li></ul></ul><ul><ul><li>decremental </li></ul></ul><ul><li>All-or-none </li></ul><ul><li>short </li></ul><ul><ul><li>1-2 msec </li></ul></ul><ul><li>voltage-gated </li></ul><ul><li>propagated </li></ul><ul><ul><li>slow </li></ul></ul><ul><ul><li>nondecremental </li></ul></ul>

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