*Will award Brainliest if correct answer is given!* Which of the following is the correct sequence of the cardiac cycle?
a. SA node, AV node, the bundle of HIS, Purkinje fibers
b. AV node, SA node, the bundle of HIS, Purkinje fibers
c. The bundle of HIS, AV node, SA node, Purkinje fibers
d. Purkinje fibers, SA node, AV node, the bundle of HIS

A. SA node, AV node, the bundle of HIS, Purkinje fibers

Explanation:

1. The conduction system of the heart -nodal system- is what allows myocardial contraction, which translates into heartbeat and pumping of blood.

This conduction system begins in the sino-atrial node (SA), which is located in the upper portion of the right atrium, and is regulated by the autonomic-sympathetic and parasympathetic nervous system.

The impulse generated in SA passes to the atrioventricular node (AV) that is located in the interventricular septum (IVS).

From AV, impulse passes to the His-Purkinje system, formed by the bundle of His, which runs along the IVS and is divided into two branches, right and left.

Purkinje fibers are born from each of the bundles of His bundle, and are distributed through the right and left ventricles.

2. As a result of the depolarization that occurs in the atrioventricular node - which undergoes a brief interruption in its path - depolarization continues in the bundle of His, which runs through the rest of the interventricular septum to divide into two branches, the right and the left.

The left branch is usually subdivided into three fascicles, the left anterior, left posterior and a central branch. Purkinje fibers are born from each of these branches and fascicles, which stimulate myocardial contraction.

3. Ventricular systole consists of contraction of the myocardium, which leads to boost blood contained in the ventricles to the lungs or general circulation. In this phase of the cardiac cycle, the semilunar valves - which allow access to the pulmonary and aortic arteries - open, which produces the second cardiac noise.

Other events that occur during systole are the increase in ventricular pressure and the closure of the atrioventricular valves (AV), to prevent ventricular blood from returning to the atria.

Hope this helps!

SA node, AV node, the bundle of HIS, Purkinje fibers .

Explanation: