Question

Pacemaker is
A. Instrument for measuring heart beat
B. Instrument for measuring pulse rate
C. AV node that provides impulse for heart beat
D. Sinoauricular node that provide impulse for heart beat

Answer 1

Hint:-The heart is the chief organ of the circulatory system. It is a highly efficient muscular organ responsible for pumping and circulation of blood throughout the body as per requirement

Complete step-by-step solution:-The heart has a conduction system which helps it to pump blood efficiently. It is a collection of nodes and specialized conduction cells. The conduction system initiates and coordinates the contraction of the heart muscle. An excitation signal is first created in the atrium by a Sinoauricular (SA) node and then travels down a specific path to reach the ventricles to complete one cycle of electrical conduction in the heart.
SA node is a collection of specialized cells which is located in the upper wall of the right auricle. It is positioned at the same junction where the superior vena cava enters. The electrical impulses generated by SA nodes spread across both auricles and result in their contraction. This allows the blood from auricles to move into the ventricles. The rate of impulses generated by the SA node is under the control of the Autonomic nervous system.
The continuous rhythmic contraction and relaxation of the heart muscle (myocardium) results in a heartbeat. The electrical impulses of SA nodes catalyse the function of each part of the conduction system to produce a normal heartbeat. This is why SA nodes are also known as the body's natural pacemakers. A normal heart rate of an adult is about 72 beats per minute.
So, the correct answer is (D), Sinoauricular node that provides impulse for heart beat.

Note:-
The cardiac conduction system consists of SA node, Auriculoventricular (AV) node, Bundle of His and Purkinje fibres. Sympathetic nervous system increases the rate of impulse generated by the SA node thus increasing the heart rate whereas the parasympathetic nervous system decreases the heart rate by decreasing the impulse generation by the SA node.