Action Potential

Resting Membrane Potentials

Flow = permeability x driving force

Driving Forces:

1. Concentration gradient

2. Electrical gradient

Electrochemical gradient

Excitable Tissues

electrically active tissues

• nervous tissue

• muscle tissue (skeletal, smooth, & cardiac)

Action Potentials

• Series of changes in the membrane potential (change from PMP).

• Occur during the transmission of an electrical signal along the cell membrane.

• Voltage changes determined by measuring at a specific point on a nerve or muscle cell membrane.

Local Potential

“Passive” Depolarization

Depolarization to Threshold

• Depolarization produced by the stimulus

  • chemical, electrical, and mechanical

• Depolarization due to what’s done to this part of the membrane

Threshold

the production of an action potential is an all-or-none response

Depolarization

“Active”/”Rapid”

• produced in response to the stimulus

• due to what this part of the membrane does

Acceleration indicates a process that positive feedback

Depolarization continues and reaches peak at about +35 mV

Repolarization

Membrane potential returns to resting level

Hyperpolarization

Membrane potential becomes even more negative, falling a little bit below resting membrane potential, and then gradually returns back to resting level.