Question

what do the terms cardiac cycle and heartbeat signify

Answer 1

Cardiac cycle means the complete rotation of blood from where the heart releases the blood to right atrium. It includes systole and diastole. And heartbeat means the rate of beating done by the heart which creates lub-dub sounds

Answer 2

cradiac cycle is the complete circulation of blood all over the body
heartbeat  is the sound produced by heart it continues to beat untill we are alive