Question

How does the concentration of potassium in the blood affect the resting membrane potential, and ability of excitable cells to reach threshold?

a. Hypokemia causes more potassium than normal to leave the cells because there is an increased concentration gradient. This raises the resting membrane potential making cells more excitable.

b. Hypokemia causes more potassium than normal to leave the cells because there is an increased concentration gradient. This lowers the resting membrane potential making cells less excitable.

Sometimes one disturbance to homeostasis can cause another! Recall that when kidneys reabsorb hydrogen ions they lose potassium ions, and when they secrete hydrogen ions they reabsorb potassium. In other words, these ions move across an antiporter in opposite directions. This means that an abnormal breathing pattern can cause a disturbance to plasma pH, that can influence potassium balance! This in turn can affect the function of excitable cells! Putting all of this together, and considering your answers to the previous two questions, choose the correct statement.

a. Hyperkalemia can be caused by hyperventilation, and results in excitable cells that depolarize less easily.

b. Hypokalemia can be caused by hyperventilation, and results in excitable cells that depolarize less easily.

c. Hyperkalemia can be caused by hypoventilation, and results in excitable cells that depolarize less easily.

Answer 1

a. Hypokemia causes more potassium than normal to leave the cells because there is an increased concentration gradient. This raises the resting membrane potential making cells more excitable.

In hypokalemia, the resting membrane potential is increased. Both action potentials and refractory periods are prolonged, as opposed to In hyperkalemia, the resting membrane potential is decreased, and the membrane becomes partially depolarized. Initially, this increases membrane excitability, above a certain level of potassium it inactivates sodium channel, opens potassium channels, than the cell becomes refractory.

Since there is more potassium ions inside the cells as compared to the outside the cell, this will create a concentration gradient, that makes potassium leave the cell.