If the membrane potential is anything other than 0 mV, it is said to be polarized.  The magnitude of membrane polarization is proportional to the concentration of ionic charges that are separated.  By convention, the ECF is said to have a charge of 0 mV.  A negative sign (-) is used to denote an excess of negative charge in the ICF, and a positive sign (+) is used to denote an excess of positive charge in the ICF  

Polarization

If the membrane potential becomes "less negative", it is said to be depolarized.  This can occur by positive ions moving into the cell or negative ions moving out of the cell.  

Depolarization

Repolarization occurs after a cell has been depolarized, that is, becomes more positive, and returns to resting potential of -70 mV.  

Repolarization

If the membrane potential becomes "more negative", it is said to be hyperpolarized.  This can occur by negative ions moving into the cell or positive ions moving out of the cell.  

Hyperpolarization

- polarization
- depolarization
- repolarization
- hyperpolarization 

Michigan State University

Nerve and muscle tissue are called "excitable" because they produce electrical signals when excited beyond their resting potential.  These electrical signals are produced by ion movement across the plasma membrane to make the ICF more positive or negative.  

Neural Communication

Sherwood, L. (2010). Human Physiology: From Cells to Systems (7th ed.). Pacific Grove (Calif.): Brooks/Cole.

Learn Before

Related

Learn After