Question

The first heart sound is produced when
(a)Intraventricular pressure decreases
(b)Semilunar valve snaps shut
(c)Bicuspid and tricuspid close quickly
(d)Diastole begins

Answer 1

Hint: There are some valves in the heart that prevent the backflow of the blood from ventricles to atria. These are located between the atria and ventricles.

Complete answer:
The first heart sound is produced by the atrioventricular valves closing. The heartbeat forms ‘lub-dub’ and the first heart sound, or S1, forms the "lub" of "lub-dub" and is made of M1 (mitral valve closure) and T1 (tricuspid valve closure). Normally T1 is followed by M1. It is caused by the closure of the atrioventricular valves, i.e. tricuspid and mitral (bicuspid) valves, at the beginning of the ventricular contraction, or systole. The second tone, "dub" or S2, is triggered by the aortic and pulmonary valve closures, which mark the end of the systole. And the time span between the first heart sound and the second sound defines systole (ventricular ejection) and the interval between the second and the next first sound defines diastole (ventricular filling).
There is also the sound of a third and fourth heart, S3 and S4. They may occur in normal people or may be associated with pathological processes. S3 and S4 are called gallops because of their cadence or rhythmic pacing. Gallops are sounds of low frequency, consistent with diastolic filling. S4 may occur in patients with very high blood pressure.

Additional Information: Our heart has four chambers. The upper two chambers are known as atria and the lower two chambers are called the ventricle. A thin, muscular wall called the interatrial septum divides the left and the right atria, while a thick-walled inter-ventricular septum divides the left and the right ventricles. Similarly, the atrium and the ventricle present in the same side are separated by the atrioventricular septum. The opening of the right atrium and the right ventricle is protected by a valve which is formed of three muscular flaps or cusps, called the tricuspid valve, Whereas a bicuspid or mitral valve protects the opening of the left atrium and the left ventricle.

So, the correct answer is ‘Bicuspid and tricuspid close quickly’.

Note: The electrocardiogram (ECG) is an electrical device used to measure the rate of heartbeat. The electrodes will be kept on the chest of a person and the signals are shown as a wave in the computer.