What happens to the resting potential of a neuron as extracellular K+ concentration is increased?


Posted on : 27-06-2013 | By : My Study Coach | In : Improve Your Concentration
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In this case, assume that there will be no change to intracellular K+ concentration. I had thought that the potential becomes more negative, especially considering no change in intracell. K+ concentration; but apparently that’s wrong. Also, what would happen to an action potential under these conditions.

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Comments (1)

Assuming that the concentrations of Na+, like the intracellular concentration of K+, does not significantly change, an increase in extracellular K+ concentration results in a decrease in resting membrane potential (that is, it becomes less negative). This, in turn, produces a decrease in the force of contraction, and the rate at which action potential travels across the muscle. In extreme cases (“hyperkalemia”), the rate may be slowed so far that “ectopic” pacemakers can emerge in the ventricles. Therefore, one of the major effects of this condition is an increase in muscle cell excitability, because their resting potential is closer to the threshold for generating action potentials, and the equilibrium potential of K+ is positively shifted, increasing the excitability of the neuron and neuronal processes. If the rate of K+ efflux is decreased, as is true in this case, then normal membrane potential will not be established, and the cell may lose the ability to generate an action potential. Therefore, excess extracellular K+ can inhibit muscle function, and could be fatal in cardiac muscle.

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