Question

Since it is the Sino-auricular node, which initiates the impulses in the heart of the mammal it is known as
A. Cholinergic
B. Adrenergic
C. Neurogenic
D. Myogenic

Answer 1

Hint: The circulatory system is of two types that are open circulatory systems in invertebrates and closed circulatory systems in vertebrates. There are four parts in the closed circulatory system. They are Heart, Arteries, Veins and Blood. The human heart is a four chambered organ present in the body. It simultaneously pumps the poor oxygenated blood into lungs and oxygenated blood to all cells of the body, through rhythmic sequence of cardiac cycle.

Complete step by step answer:
-Cardiac cycle- The pumping action occurs in a rhythmic sequence of contraction and relaxation of heart muscle.
-The one cardiac cycle completes in 0.8 seconds, by two different phases. They are: Diastole and Systole.
For one complete beat, the heart pumps 70 ml of blood.
-The muscle has its own beat which was carried by SA-node (sino-auricular node).
Sino-atrial nodes are also known as the natural pacemaker. It is present in the upper wall of the right atrium.
-The SN node which is responsible for heart beats and also conducts the electric signals to all cells of the heart muscle.
-This electric impulse is initiated by myocytes. Which is responsible for contraction of cardiac cycle.
-This SA node initiates and passes its signal to the atria and then to the AV node (atrioventricular) node and apex of heart and the walls of ventricles.
-If this SA node was defective, another SA node was replaced artificially by therapy. That pacemaker is known as an artificial pacemaker.
Since it is the Sino-auricular node, which initiates the impulses in the heart of the mammal it is known as myogenic. So, the correct answer is option (D).

Note: The electric signals which were generated by the SA node are likely the same as the neuro signals but not neurogenic. Usually the ECG (electrocardiogram) is used to detect the defects in the cardiovascular system.