Anatomy Exam 4 - Resting membrane potential

factors that make the cell more negatively charged on the inside and more positively charged on the outside at rest

1. The plasma membrane has more K+ leak channels than Na+ leak channels, therefore, the number of K+ ions that leave the cell is greater than the number of Na+ ions that enter the cell. This results in the inside of the membrane being increasingly negative and the outside being increasingly positive. 2. Trapped anions cannot follow K+ out of the cell because they are attached to non-diffusible molecules such as ATP and large proteins inside the cell. 3. The sodium-potassium pump expels 3 Na+ ions for every 2 K+ ions imported, thus losing more positive than gaining

Resting membrane potential

An electrical potential difference (voltage) that exists across a plasma membrane of an excitable cell when the cell is in an undisturbed state (resting)

are there more potassium or sodium leak channels in the plasma membrane?

The plasma membrane has more potassium leak channels than sodium leak channels, therefore, the number of K+ ions that leave the cell is greater than the number of Na+ ions that enter the cell. This results in the inside of the membrane being increasingly negative and the outside being increasingly positive.

function of the sodium potassium exchange pump

These pumps help maintain the resting membrane potential by pumping out NA as fast as it leaks in. At the same time, the pump brings back K, but it eventually leaks back out. 3 Na are expelled for every 2 K, thus, losing more positive than gaining. Total contribution is small, however, only about -3 of the -70mV.

sodium potassium exchange pump's relationship to the electrochemical gradient of sodium and potassium

sodium and potassium ions are pumped in opposite directions across the membrane building up a chemical and electrical gradient for each. These gradients can be used to drive other transport processes. In nerve cells the pump is used to generate gradients of both sodium and potassium ions. These gradients are used to propagate electrical signals that travel along nerves. Therefore the action of nervous tissue requires ATP to generate resting potentials

If a membrane were freely permeable to sodium, what would occur?

the influx of Na+ would continue until the equilibrium potential was reached

If a membrane were freely permeable to potassium, what would occur?

the outflow of K+ would continue until the equilibrium potential was reached