Heart and Action Potentials

[ohword3]

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Which quadrant of the heart has the most action potentials? Would it be the LV because it is the largest section or the RA because of the SA node?

I think it's RA because the AP in the LV is passed through the intercalated disc, correct?

 

[sps27]

Which quadrant of the heart has the most action potentials? Would it be the LV because it is the largest section or the RA because of the SA node?

I think it's RA because the AP in the LV is passed through the intercalated disc, correct?

Wow......never thought of that. Not sure but I also happen to think it is RA because it has SA and AV node and the electrical impulses originate at SA. But the contraction in LV is from the bottom up i.e., apex to base, so that is a bit confusing......anyways.....if it came in an exam I would have marked RA.....🙂

 

[anticarbon]

Doesn't intercalated discs spread the 'action potentials' to downstream cells by ion exchange between the cells?

RA does have SA+AV nodes, but the nodes are quite small compared to the heart so even with RA+SA+AV, wouldn't LV outnumber in cell population and therefore correct answer to this specific question? Finally, shouldn't we be excluding the nodes because although they essentially function for the heart, they aren't part of the heart organ?

I think I brought up more questions than answering the OP's question...

 

[sps27]

Doesn't intercalated discs spread the 'action potentials' to downstream cells by ion exchange between the cells?

RA does have SA+AV nodes, but the nodes are quite small compared to the heart so even with RA+SA+AV, wouldn't LV outnumber in cell population and therefore correct answer to this specific question? Finally, shouldn't we be excluding the nodes because although they essentially function for the heart, they aren't part of the heart organ?

I think I brought up more questions than answering the OP's question...

U got me. I agree with you totally, but still not sure about the ans. Also, what are these intercalated discs and what do they have to do with action potentials? Are these specific to the bundle of his or purkinje fibers or are they part of the cardiac muscle fibers?

 

[anticarbon]

Intercalated discs allow ion exchange that depolarizes downstream cells, just like how Na+ influx from extracellular space causes depolarization. It allows coordinated contraction of the heart.

Bundle of his and subsequently dividing smaller Purkinje fibers are the main sources of AP that starts a few heart cells to excite, which those cells then will depolarize the cells downstream by ion exchange through intercalated discs.