Rate of heart beat is determined by

(A)Purkinje fibres
(B)papillary muscles
(C)AV node
(D)SA node

The NCERT line that answers it

Verbatim line

The SAN can generate the maximum number of action potentials, i.e., $70-75 \text{ min}^{-1}$ , and is responsible for initiating and maintaining the rhythmic contractile activity of the heart.

Chapter: Body Fluids and Circulation
Section: 15.3.1 Human Circulatory System

The answer appears as a continuous sentence in NCERT. This is that sentence.

How this line gives the answer

75, emb=1.0, combined=0.9). Verified: high — The span explicitly states that the SAN generates the maximum number of action potentials (70-75 min⁻¹) and is responsible for initiating and maintaining rhythmic contractile activity, which directly establishes it as the pacemaker determining heart rate.

We did this for 1,565 questions.

Every one traced to the exact sentence in NCERT that answers it, including 90% of the 2026 paper. Sit a mock on the real NEET 2027 computer interface and every mark you drop comes back with its line attached.

Take the free 5-minute check More from this chapter

Question text is reproduced from the published NEET 1999 paper for study and commentary. NCERT text is quoted, not redistributed; textbooks remain at ncert.nic.in. Our mapping method, including its measured error rates, is published at /methodology.