Hyper/hypokalemia

[mimosa2411]

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I have read from my physiology book that:

"Ions whose equilibrium potential Ex is positive than Vm will always give a depolarization of the membrane when opening a channel for the ion"

But today my teacher told my that
Hypokalemia : decreased ECF(extracellular fluid) in compared to the ICF (intracellular) [ K +] concentration Ek( equilibrium potential) will increase and will thereby hyperpolarize Vm (more negative).

What I think is when the Ek is more positive than Vm the cell will be depolarize and not hyperpolarize. Can anyone please help me.

 

[ZX10R]

Use nerst equation. There's going to be even less [K]+o (extracellular potassium) driving the equilibrium of K towards the outside. This will happen because K has the highest conductance (G) than any other ion; so if there is less Ko from Ek[[k+]o/[K+]i] using Le Chateliers principle more K will move out of the cell, thus hyperpolarizing the cell.

This is also why the heart can stop in (Hyper)kalemia cells will naturally depolarize to a point where Na+ sodium voltage gated channles will no longer activate. Why does hyperkalemia occur? because as the heart becomes ischemic the dead tissue releases large amounts of K+, or some person in the hospital doesn't measure right and puts to much K+ in.

 

[repititionition]

Use nerst equation. There's going to be even less [K]+o (extracellular potassium) driving the equilibrium of K towards the outside. This will happen because K has the highest conductance (G) than any other ion; so if there is less Ko from Ek[[k+]o/[K+]i] using Le Chateliers principle more K will move out of the cell, thus hyperpolarizing the cell.

This is also why the heart can stop in (Hyper)kalemia cells will naturally depolarize to a point where Na+ sodium voltage gated channles will no longer activate. Why does hyperkalemia occur? because as the heart becomes ischemic the dead tissue releases large amounts of K+, or some person in the hospital doesn't measure right and puts to much K+ in.

Ok, I'm stupid and barely remember the names of the equations in the above post, much less the equations themselves, so I think about it this way (call off the physiology police. this is just how I remember, not claiming mechanistically correct):

• normal place for high K+? intracellular

• normal place for low K+? extracellular

• normal cell RMP? negative (polarized) due in large part to big K+ gradient (RMP basically a fxn of K+ permeability)

• this sets up our baseline: the gap between K+(intracellular) and K+(extracellular)

• taking either of these variables FURTHER in their physiological directions (raising intracellular K+ or lowering extracellular K+) will MAGNIFY the physiological baseline.

• So plasma hypokalemia hyperpolarizes, and by extension, plasma hyperkalemia depolarizes.

• To finish this topic off, hyperkalemia causes weakness because of chronic low-level Na+ channel inactivation (remember 3 states of the Na+ channel, open, closed, and inactivated) due to transient depolarizations caused by higher baseline membrane potential.

 

[mimosa2411]

Use nerst equation. There's going to be even less [K]+o (extracellular potassium) driving the equilibrium of K towards the outside. This will happen because K has the highest conductance (G) than any other ion; so if there is less Ko from Ek[[k+]o/[K+]i] using Le Chateliers principle more K will move out of the cell, thus hyperpolarizing the cell.

This is also why the heart can stop in (Hyper)kalemia cells will naturally depolarize to a point where Na+ sodium voltage gated channles will no longer activate. Why does hyperkalemia occur? because as the heart becomes ischemic the dead tissue releases large amounts of K+, or some person in the hospital doesn't measure right and puts to much K+ in.

Thank you so much for helping. 🙂

I understand the use of Le Chateliers principle but I have to compare the new "Ek" (Nernt's potential for potassium) with the "Vm" membranpotential. And does that mean that the Ek is lower than the Vm and because of that it will cause big driving force and the result must be an outward flux of potassium ions(=hyperpolarization)?

 

[mimosa2411]

Ok, I'm stupid and barely remember the names of the equations in the above post, much less the equations themselves, so I think about it this way (call off the physiology police. this is just how I remember, not claiming mechanistically correct):

• normal place for high K+? intracellular

• normal place for low K+? extracellular

• normal cell RMP? negative (polarized) due in large part to big K+ gradient (RMP basically a fxn of K+ permeability)

• this sets up our baseline: the gap between K+(intracellular) and K+(extracellular)

• taking either of these variables FURTHER in their physiological directions (raising intracellular K+ or lowering extracellular K+) will MAGNIFY the physiological baseline.

• So plasma hypokalemia hyperpolarizes, and by extension, plasma hyperkalemia depolarizes.

• To finish this topic off, hyperkalemia causes weakness because of chronic low-level Na+ channel inactivation (remember 3 states of the Na+ channel, open, closed, and inactivated) due to transient depolarizations caused by higher baseline membrane potential.

It was definitely helpful.
Thank you so much for helping.
I have to compare the new "Ek" (Nernt's potential for potassium) with the "Vm" membranpotential. And does that mean that the Ek is lower than the Vm and because of that it will cause big driving force and the result must be an outward flux of potassium ions(=hyperpolarization)?

 

[Ismet]

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Closing thread.