Chapter 5

• Usually, the inside of a cell membrane holds a more negative charge at rest because of the high concentration of Potassium (K+) ions in comparisson to the outside.
• There is a higher concentration of Sodium and Calcium outside the cell membrane.

When a cell is at rest, most of the protien channels within the membrane are closed. However, there are occasional potassium channels that remain open, allowing K+ ions to flow freely in and out of the membrane.

• To restore the "normal" concentration gradient within cells
• These pumps constantly pump 3Na+ ions out & 2K+ ions inside the cell which contributes to the general overall more negative inner charge.

The presence of Protien anions (Pr-) within the ICF greatly contributes to the negative inner charge.

Calcium (Ca++)

Membranes at rest are 40x more permeable to K+ ions compared to Na+ ions, becaus they have more "open leakage channels" for potassium.

The actual value reflects which ion is mostly moving across the membrane at any given time. (Which happens to be K+)

-90mV

+60 mV

Inside verses outside the cell becomes LESS NEGATIVE.

Inside verses outside the cell becomes MORE NEGATIVE.

Returning to the resting membrane potential from either direction.