1. Membrane Potential
Department of Biology, WCU

2. Introduction Communication (e.g., nerve-nerve, nerve-muscle) Summary
forces leading to membrane potential
actions beyond RMP

3. Potential Voltage determinant on ions Plasma membrane causes potential
Measurement
+20 to -200 mV
polarized

4. Forces acting on ions
Na+, K+ concentration gradient caused by plasma membrane
RMP (passive movement)
Na+ permeability low
K+ permeability high
only at plasma membrane

5. Resting Membrane Potential

6. Forces acting on ions
Na+ influx and K + efflux

7. Ions causing gradient Major Minor Na+, K+ Ca++, PO4-, HCO3-
Solutes - glucose, urea

8. Potentials as signals Communication (neurons) Signal types
receiving, integrating, sending
Signal types
Graded potentials
Action potentials

9. Electrical events 1. Depolarization less potential difference
inside of cell becomes less negative
increase in Na+ influx (5,000x)

10. Electrical events 2. Hyperpolarization more potential difference
inside of cell becomes more negative
increase in K+ efflux (10x)

11. Graded potentials Short-lived changes
Decrease strength away from stimulus

12. Graded potentials Types (depend on stimulus source)
Receptor potential (light, heat)
Postsynaptic potential (neurons - synapse)

13. Action potentials Communication (neurons, neurons - muscle)
No decrement of decrease
Four phases
RMP
depolarization
repolarization
hyperpolarization

14. Action potentials