Question

Mr. Thompson is admitted to the hospital for cardiac problems. Unfortunately for him, one of the nurses got the solutions mixed up that he was supposed to receive intravenously. Instead of getting a solution that had the concentrations of ions similar to what he normally has in his blood, he got a solution with extremely high levels of K⁺ (equal to the levels of K⁺ normally found inside his cells). How do you think this mistake would change the resting membrane potentials of his neurons (assuming they’re exposed to the infused solution)? How would this mistake impact the ability of his neurons to fire action potentials with high frequency? Explain your answers.

Answer 1

In normal cell, there is more potassium ions inside the cell with respect to outside the cell, where there is more sodium ions, this contributes to the resting membrane potential of about -90 mV, but when the levels of potassium ions are increased extracellularly the resting membrane potential is shifted to less negative values, that is from -90mV to -80 mV, this will move resting membrane potential closer to normal threshold potential of -75 mV resulting in increased myocytic activity.

With increased potassium concentration extracellularily, the cells can never generate an action potential by itself, this happens because above a certain level of potassium, the depolarization inactivates sodium channels, opens potassium channels and thus the cells become refractory and the cellls are less likely to fully depolarize to cause another action potential to be generated.