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Affects of calcium, potassium and sodium on heart rate

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I found that calcium ions don't change the heart rate dramatically and that potassium and sodium ions lower heart rate.
I am trying to figure out why this is though.

Please let me know:
1) Why calcium ions don't change the heart rate dramatically...
2) Why potassium ions lower the heart rate
3) Why sodium ions lower the heart rate.

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****Please provide the reference to which you come upon your claim about calcium, for #1. Personal literacy search, lab work, or statement from a heart expert or instructor?

*****Research is listed, which gives credence to the idea of how calcium affects heart rate.

Some ideas to consider, with regard to calcium follow.

With a literature review, it seems apparent one way to evaluate the effect of calcium ions on the heart is by evaluating the effect of calcium channel blocking drugs. The way they work is by blocking the channels used by calcium ions. Review some of the research (noted below) and you'll likely agree that it appears to indicates that calcium channel blockers are effective at lowering the heart rate and blood pressure by blocking part of the action of calcium ions on the vascular muscles. Find the relevant articles and abstracts below.

Am J Med. 1984 Aug 31;77(2B):2-10.

Cellular actions and pharmacology of the calcium channel blocking drugs.
Katz AM, Hager WD, Messineo FC, Pappano AJ.

"The calcium channel blockers represent a group of diverse chemical structures that block calcium-selective channels in the plasma membranes of a variety of excitable cells. As the calcium fluxes carried by these channels allow the calcium ion (Ca2+) to gain access to the cell interior, where calcium serves as an activator messenger, calcium channel blockers generally act to inhibit cell function. By reducing the depolarizing currents caused by the entry of positively charged Ca2+ into the negatively charged interior of resting cells, the calcium channel blockers also inhibit excitatory processes that depend on calcium entry across the plasma membrane. These principles account for most of the effects of calcium channel blockers on the cardiovascular system. The calcium channel blockers inhibit contractile function in the heart and vascular smooth muscle and, because the initial ...

Solution Summary

Critical to normal heart functioning, depending on the ratio and use of sodium, potassium and calcium are discussed.