Questions roughly speaking ions and majority heart amusement?

Excessive amounts of each of the following ions would likely interfere with commonplace heart activity. Note the type of changes caused within each case.

K+

Ca2+

Na+

Please help me. I hold no idea how to answer this and i can't find the answer!
Answers:
Excessive potassium (K), also known as hyperkalemia, causes impairment of cardiac electrical conduction through the depolarization of membrane potentials surrounded by cells which can result in arrhythmias, most concerning of which are ventricular fibrillation and asystole.

Excessive calcium (Ca), also known as hypercalcemia, cause shortened QT intervals and a widened T wave on ECGs. This is due to irregular re-polarization of cardiac cells.

Excessive sodium (Na), also set as hypernatremia, causes cardiac arrhythmias, especially tachycardias (fast heart rate). Source(s): http://en.wikipedia.org/wiki/Hyperkalemi…
http://en.wikipedia.org/wiki/Hypercalcem…
http://emedicine.medscape.com/article/24…

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