Question

The function of the SA node is the
(a) Muscular pàin
(b) Contraction of lungs
(c) Heartbeat
(d) None of the above

Answer 1

Hint: The whole heart is made of cardiac muscles. It has a specialized cardiac musculature called the nodal tissue is also distributed in the heart known as the sinoatrial node is mainly responsible for conducting contraction and relaxation of the heart muscles. This particular activity creates a lub-dub sound of the heart.

Complete answer:
The sinoatrial node also known as the SA node is a banana-shaped structure, its function is to ensure a heartbeat, located in the inner wall called myocardium of the right atrium of the heart. It is located laterally to the entrance of the superior vena cava in a region called the sinus venarum. This means it is positioned roughly between a groove called the crista terminalis that runs between the entrance of the superior vena cava and the inferior vena cava. These cells have the ability to produce an electrical impulse that travels through the heart.
The main function of a sinoatrial node cell is to initiate action potentials of the heart that can pass through cardiac muscle cells and cause contraction. The contraction of cardiac muscle or heart muscle in all animals is initiated by electrical impulses known as action potentials. The rate at which these impulses fire, controls the rate of cardiac contraction known as the heart rate. The cells that create these rhythmic impulses are called pacemaker cells; they are setting the pace for the pumping of blood, and they directly control the heart rate. Hence the function of the SA node is to ensure heartbeat. They make up the natural pacemaker of the heart also known as the cardiac pacemaker.
So, the correct answer is, 'Heartbeat'.

Note: -In a healthy heart, the SA node continuously produces action potential without the presence of any external stimuli.
-The SA node is setting the rhythm of the heart and so it is known as the natural pacemaker of the heart.
-The rate at which the electric impulses or action potential fires, controls the rate of cardiac contraction called the heart rate.