A: Elevated levels of Na^+ decrease the heart | vedclass

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(D) Elevated levels of $Na^+$ (sodium ions) in the blood interfere with the influx of $Ca^{2+}$ ions into the cardiac muscle cells.Since $Ca^{2+}$ is

Vedclass · Accepted Answer

Both Assertion and Reason are incorrect.

Vedclass · Answer

(D) Elevated levels of $Na^+$ (sodium ions) in the blood interfere with the influx of $Ca^{2+}$ ions into the cardiac muscle cells.Since $Ca^{2+}$ is essential for the contraction of cardiac muscles,an excess of $Na^+$ inhibits this process,leading to a decrease in heart rate and contractility.Therefore,the Assertion is incorrect.Furthermore,elevated $Na^+$ levels do not increase the excitability of the $SA$ node; in fact,they tend to depress cardiac function.Thus,the Reason is also incorrect.

$A$: Elevated levels of $Na^+$ decrease the heart rate and contractility.
$R$: Elevated $Na^+$ levels increase the excitability of the $SA$ node.

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$A$: Elevated levels of $Na^+$ decrease the heart rate and contractility.$R$: Elevated $Na^+$ levels increase the excitability of the $SA$ node.