Question

the rhythmic contraction followed by expansion ofbheart muscles​

Answer 1

Answer:

Cardiac cycle is the rhythmic expansion and contraction of heart.

Contraction is called cardiac systole

Relaxation is called cardiac diastole

Together they known as cardiac cycle.

The rhythmic sequence of contractions of the heart is coordinated by two small groups of cardiac muscle cells called the sinoatrial (SA) and atrioventricular (AV) nodes.

Hence the rhythmic expansion and contraction of the heart are called Cardiac cycle.

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Answer 2

Answer:

The rhythmic contraction and expansion of the heart is a Cardiac cycle. ... Blood is pumped out of the heart during contractions, whilst the heart is filled with blood during relaxation.