Hyperkalemia - The effects of hyperkalemia on resting membrane potential - depolarized - why & how

The effect of hyperkalemia on Resting Membrane Potential.
1. Introduction:
a. Hyperkalemia: Increased K+ level in the blood Increase extracellular potassium level.
b. The Equilibrium potential for K+ is -90 mV.
c. The resting membrane potential is maintained by the ion that has the highest conductance through its membrane during resting. In this case, K+ has the highest conductance at rest. Therefore, K+ electrochemical gradient has the most effect the membrane potential. The resting membrane potential tends to move towards K+ equilibrium potential.
d. Normally, there are more potassium inside the cell (more intracellular potassium) than they are outside of the cell (less extracellular potassium)
e. In this video, I will talk about the resting membrane potential of cardiac myocytes with is around -90mV. The high conductance of K+ through the leak channels in its membrane brings the resting membrane potential towards its equilibrium potential.


1. So on the left is the normal cell. As you can see that there are leak channels on the cell membrane for both Na+ and K+, however, there are much more leak channels K+ than for Na+. Therefore, the conductance for K+ is much greater than for Na+. For this reason, K+ is the main ion that is used to maintain resting membrane potential.
a. Under normal condition, resting membrane potential is around -90mV and there are more potassium inside the cell (more intracellular K+) than outside of the cell. K+ is freely moving into and out of the cell through the leak channel to maintain this electrochemical gradient at resting and there are no net movement of the ion into or out of the cell (intra or extracellularly).
2. However, when there is hyperkalemia. An increase level of potassium in the blood, which means that there is an increased level of potassium outside of the cell (extracellularly). Now the chemical gradient for K+ has been changed, and that change cause a change in the resting membrane potential. Since we have disrupted the chemical equilibrium for K+ ion, with more K+ outside the cell the net flow of K+ will be into the cell until a new electrochemical gradient has been established. Thus, there will be more K+ inside the cell. More positive ion inside the cell causes the cell to become less negative (depolarize). Under normal condition, the resting membrane potential of cardiac myocyte is around -90mV. A patient with hyperkalemia, their new resting membrane potential maybe -85mV or -80mV, the cells have been depolarized (less negative) because K+ is trapped inside.


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I tried my best to explain these concepts to the best of my knowledge and made it as simple as possible. I hope that you might find them helpful while you are reviewing your materials for your steps! Good luck to you all!

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