The Nerve Impulse Seen from Outside

Dexter M. Easton July 2000 ©

Observations on the action potential of sciatic nerve of frog
~ A teaching module ~

Table of Contents

Introduction

Part I: Some background about the membrane of the nerve cell

  1. Electric currents flow in nerve
  2. Nerve membranes can be viewed as electrical circuits
  3. Channels in nerve membrane are pathways for current
  4. Na+ and K+ inside and outside are available to carry current
  5. The force of diffusion becomes a voltage
  6. Na+ and K+ distributions are responsible for separate batteries
  7. Diffusion potential is exemplified by the "Nernst potential"
  8. Na+ and K+ act together in "Nernstian" fashion
  9. Conductance channels open during impulse
  10. Origin of the external currents
  11. After-hyperpolarization" currents
  12. Action potential up or down?
Part II: Action potential in whole nerve
  1. The subject: the sciatic nerve isolated from a frog leg
  2. Stimulating and recording arrangements
  3. Stimulating arrangements; the stimulus artifact
  4. Electrical arrangements at the recorded end of the nerve
  5. Longitudinal currents at the recorded end, cut and healed
  6. Cut end diminishes trailing currents
  7. After-potentials
  8. Increasing stimulus excites more fibers
  9. Second elevations: a second spike
  10. Very slow impulses: "C" fibers
  11. Impulse velocity
  12. Stimulation locus
  13. Reversal of stimulus current direction
  14. Conditioning-testing
  15. Conditioning-testing: local response
  16. Strength-duration curve
  17. The AP as a spatial event
  18. Volume conduction

Part III: Muscle and neuromuscular synapse

31.   Gastrocnemius muscle stimulation via nerve
32.   End-plate potential (EPP)
32_1.  Decline of currents during time
32_2.  Leading and tailing currents
32a.  S2-EPP sums with decaying S1-EPP to yield AP
32b.  Gastrocnemius Neuromuscular Facilitation
32c.  EPP facilitates nonpropagated AP
33.   Sartorius direct muscle stimulation
34.   Sartorius Impulse Latency
34a.  Distance vs elapsed time
35.  Sartorius conditioning-testing
35a.  2-pulse recovery curve

Introduction     First topic

This course is offered through the
Department of Biological Science
Florida State University