Question:medium

Given below are two statements: one is labelled as Assertion A and the other is labelled as Reason R
Assertion A: Cardiac excitation normally begins in the sinoatrial (SA) node.
Reason R: SA node cells do not have a stable resting potential. They depolarize to threshold spontaneously.

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SA Node = Primary Pacemaker of the heart.
Mechanism: Unstable resting potential (Pacemaker Potential driven by $I_f$ "funny" $\text{}^+$ currents) $\to$ Spontaneous intrinsic depolarization.

Updated On: Jul 28, 2026

Both A and R are correct and R is the correct explation of A
Both A and R are correct but R is NOT the correct explation of A
A is correct but R is not correct
A is not correct but R is correct

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The Correct Option is A

Solution and Explanation

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Given below are two statements: one is labelled as Assertion A and the other is labelled as Reason R Assertion A: Cardiac excitation normally begins in the sinoatrial (SA) node. Reason R: SA node cells do not have a stable resting potential. They depolarize to threshold spontaneously.

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The Correct Option is A

Solution and Explanation

Top Questions on Human physiology

Questions Asked in CUET (PG) exam

Given below are two statements: one is labelled as Assertion A and the other is labelled as Reason R
Assertion A: Cardiac excitation normally begins in the sinoatrial (SA) node.
Reason R: SA node cells do not have a stable resting potential. They depolarize to threshold spontaneously.