The correct option is (c) 2 and 3 only.
Explanation
The heart is a muscular organ composed of specialized cardiac muscles. Its primary function is to pump blood throughout the body via the circulatory system, a process driven by the continuous movement of these muscles.- Statement 1 is Incorrect: The muscles of the heart do not remain static. The walls of the heart chambers are made of cardiac muscles that contract and relax rhythmically. This movement is fundamental to the heart's function as a pump; if the muscles remained static, blood circulation would cease.
- Statement 2 is Correct: A heartbeat is scientifically defined as the rhythmic contraction (systole) followed by relaxation (diastole) of the heart muscles. This cycle creates the pressure required to push blood through the chambers and into the blood vessels.
- Statement 3 is Correct: Cardiac muscles are involuntary muscles, meaning their activity is not under conscious control. The heart continues to beat rhythmically throughout a person's life, including during sleep, regulated by the autonomic nervous system and the heart's internal pacemaker (sinoatrial node).
Key Takeaway: A heartbeat consists of the continuous, involuntary rhythmic contraction and relaxation of cardiac muscles, which persists throughout an individual's life to maintain blood circulation.