Define resting membrane potential and its physiological function in cells.

All cells are contained within a membrane. The resting membrane potential refers to the difference in voltage between the fluids inside of a cell and the fluids outside of a cell when a cell is in its 'resting' state. The resting membrane potential is generally -70 to -80 millivolts (mV). This is because the inside of the cell contains more electrically charged ions with a negative charge. The inside of the cell contains a high...

All cells are contained within a membrane. The resting membrane potential refers to the difference in voltage between the fluids inside of a cell and the fluids outside of a cell when a cell is in its 'resting' state. The resting membrane potential is generally -70 to -80 millivolts (mV). This is because the inside of the cell contains more electrically charged ions with a negative charge. The inside of the cell contains a high concentration of negatively charged particles, as well as a low concentration of positively charged sodium (Na+) and potassium (K+) ions. Outside of the cell there is a higher concentration of Na+. Particles in a fluid flow from high concentration to low concentration so that they are evenly distributed. K+ naturally wants to flow out of the cell and Na+ wants to flow into the cell to even out this concentration gradient. The membrane keeps most of the the channels through which Na+ flows into the cell closed when it is at rest. Additionally there are channels that pump extra Na+ ions out of the cell. In this way the cell actively maintains the resting membrane potential.

The electrical potential is physiologically important because it allows cells to transmit electrical signals. If an excitable cell, such as a nerve, muscle, or endocrine cell, receives a stimulus that raises its charge to -55mv, the Na+ channels open up allowing Na+ ions to rush into the cell. This causes a further increase in charge up to +30mv. This rapid change in membrane potential allows nerve cells to transmit signals, causing muscle cells to contract or endocrine cells to release hormones, among other things.