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I went through a number of old threads about these issues, but there is a ton of conflicting information and rightfully so because its a very confusing topic. I was just wondering if someone could verify everything I have gathered from that, and if there is anything else high yield that we need to know:
1. Hypokalemia decreases resting membrane potential, and this increases excitability BECAUSE decrease extracellular potassium levels disallow potassium channel functioning during phase III of the AP. This is similar to hypercalcemia's affect on nerves (and possible cardiac pacemaker cells?) because calcium inhibits the action of Na channels in nerve, decreasing AP propagation. This prolonges the QT also.
2. Hypokalemia also increases contractility, in a mechanism similar to digoxin, whereby the na/k atpase cannot function as effectively causing calcium buildup in the cell.
3. Conversely, hyperkalemia increases RMP. This decreases excitability because more sodium channels are in an inactivated state.
4. Is any of this related to how hypercalcemia shortens QT and hypocalcemia prolongs QT? I feel like the concepts are connect but i just can't make the connection.
1. Hypokalemia decreases resting membrane potential, and this increases excitability BECAUSE decrease extracellular potassium levels disallow potassium channel functioning during phase III of the AP. This is similar to hypercalcemia's affect on nerves (and possible cardiac pacemaker cells?) because calcium inhibits the action of Na channels in nerve, decreasing AP propagation. This prolonges the QT also.
2. Hypokalemia also increases contractility, in a mechanism similar to digoxin, whereby the na/k atpase cannot function as effectively causing calcium buildup in the cell.
3. Conversely, hyperkalemia increases RMP. This decreases excitability because more sodium channels are in an inactivated state.
4. Is any of this related to how hypercalcemia shortens QT and hypocalcemia prolongs QT? I feel like the concepts are connect but i just can't make the connection.