Question

Why Can't Systole occur in ventricles and atriums at the same time?

Answer 1

Answer:

Systole means the contraction of the heart chambers and the diastole means the relaxation of the heart chambers.

Human heart is divided into four chambers; right and left atrium and the right and left ventricles.

The main function of the human heart is to pump the blood throughout the body tissues and this complete process is called as a cardiac cycle.

The total duration of a cardiac cycle is 0.8 seconds and this signifies that the total blood volume of the body which is around 5 liters gets distributed throughout the body tissues within the same time duration.

Also, the heart is made of the nodal tissues which are self excitatory in nature that is they can operate and monitor their beatings on their own. One such tissue is the SA node (sinoatrial node). It is called so as it is present in the right atrium of the human heart. This nodal tissue is responsible for the initiation of the heart beat and thus is also called as the pacemaker. Also, the information from the SA node needs to be passed on to the other nodal tissue called as the AV node (atrio-ventricular node) located within the junction of the atrium and ventricles. This is also called as the pace setter. From the AV node the information gets passed on to the right and left bundle of His and then from the Purkinje fibers it remains communicated throughout the ventricles.

Thus, we get to see that there is a time lag between the working of the atrium and the ventricles.

The initiation of the cardiac cycle is the pouring of the blood into the right atrium of the heart from the superior, inferior vena cava and the coronary sinuses. Thus, the pressure on the atrium increases and they contract; termed as atrial systole.

They however need to reduce their pressure and this happens due to the opening of the atrio-ventricular valves (tricuspid valve between right atrium-ventricle and bicuspid valve between left atrium-ventricle). Due to this now the blood enters into the ventricles from the atrium. This makes the ventricles undergo contraction (ventricular systole) whereas relaxation of the atrium (atrial diastole).

A phase of joint systole that is the phase in which the atrium and the ventricles would be contracted together can lead to the complete failure of the heart functioning and it might lead to the heart collapse because of the immense increase in the pressure. Thus, a joint systole never takes place in the different heart chambers.