Question

List the pathway the electrical impulse takes from the right atrium to cause the left ventricle to contract. In other words, describe the pathway of the intrinsic electrical system of the heart to the left ventricle.

Answer 1

1. SA NODE- Impulse generation -  the impulses start here first, in a small group of specialised cells located in the right atrium. SA node is called the natural pacemaker. so, first the SA node gets self excited and causes the right atrium to contract.
2. The impulses produced in the SA node travel into the walls of the left atria and cause them to contract aswell at the same time. when the atrias contract, This forces blood into the ventricles. (here, the ventricles are in relaxed state).
3. The impulses from the SA node reach the AV node - here, the impulses slows for a moment before they get to the ventricles.
4. The impulse travels through a pathway of fibers called the bundle of his and the purkinje fibers. First, the bundle of His gets excited when it recieves the impulses, this branches out into right bundle branch and the left bundle branch. the right bundle branch goes on to the right side of the heart and it excites the right side of the purkinje fibers. Where as the left bundle branch, goes iand excites the left side of the purkinje fibers which causes the left ventricle to contract. These both spead the impulses into the ventricles and causes them to contract. This contraction causes the blood to flow out of the heart and into the lungs and into the various organs.
5. This cycle of SA node generating its own impulses begins again and so, another one of this cycle begins.

the pathway include for contraction of right atria to left ventricle-

1. SINO ATRIAL NODE (SA) EXCITATION
2. RIGHT ATRIUM CONTRACTS (along with left atrium)
3. ATRIOVENTRICULAR NODE (AV) EXCITATION
4. BUNDLE OF HIS EXCITATION
5. LEFT BUNDLE BRANCH EXCITATION
6. LEFT SIDE PURKINJE FIBERS EXCITED
7. LEFT VENTRICLE CONTRACTS.