Please help with cardiac action potential question

[deleted-646951]

Hello there,
I have a query relating to the cardiac action potential.
An injection of potassium is used to stop a person’s heart in the lethal injection and open heart surgery because it interferes with the electrochemical gradient and causes heart arrythmia. But how does it actually do this on a basic level please? Potassium levels are higher in the cellular cytoplasm and sodium levels are higher extracellular space. I don’t really understand how a potassium injection disrupts sodium ions outside the cell and such like.
Sure, the potassium injection would introduce large quantities of potassium into the extracellular space but how does that stop sodium and potassium switching during depolarization and repolarization?
Please help it’s doing my head in thank you.



EDIT HERE: I mean this is how I currently understand it and if I am wrong then please correct me and put me on the right track.

So the concentration gradient of sodium drives it into the cell as there’s more sodium outside; because the cell’s interior is negatively charged and sodium is a positively charged ion, sodium Again is driven into the cell’s interior.
Potassium also is driven inward by its electrical charge as its again positive and driven toward the cell’s interior (negative) however because the potassium levels outside are lower than inside, it’s driven outward by its concentration gradient.
When a large dose is introduced of a potassium solution it stops the potassium inside the cell having any pull outside as it negates the concentration gradient which was pulling potassium outside and now there is only the electrical charge gradient pushing potassium into the negatively charged cell’s interior.
This means that the potassium/sodium switch stops and potassium no longer leaves the cell because the concentration gradient has been destroyed which means there’s no reason to go outside.
Correct?


As a result the sodium also stops moving and the action potential is not able to be carried out inducing cardiac arrest and death of the inmate being executed by a lethal injection and suchlike?

[deleted-70304]

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