> ? Moving to the next question prevents changes to this answer Question 8 Which

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> ? Moving to the next question prevents changes to this answer Question 8 Which of the following best represents the order of structures across which electrical i'Mpulses fhow during the cardac oycle? AV node--> SA node-> Bu die branches--> Purkinje fibers-> Heart apex O SA node-> AV node- Bundle branches-> Heart apex-> Purkinje fibers o Bundle branches->Purkinje fibers- >AV nodeSA node> Heart apex Purkinje fibers >Bundle branches->AV node Heart apex-SA node Heart apex-> SA node->AV node->Purkinje fbers- Bundle branches Moving to the next question prevents changes to this answer arch

Explanation / Answer

Answer

2. SA Node - - - AV Node - - - Bundle Branches - - - Heart Apex - - - Purkinje fibres.

Cardiac cycle is referred to a set of events that take place from the beginning of a heart beat to the beginning of the next heart beat. This involves the contraction and relaxation of the four chambers of the heart namely auricles and ventricle which are in 2 number each. Heart is a muscular organ which requires electrical signals or impulses to induce contraction and relaxation of the muscles. These contractions and relaxations help in the functioning of heart i.e., pumping blood to the whole body.

The electrical impulses start from the Sinoatrial node or SA node situated in the right auricle of the heart. These impulses contract the auricles resulting in the movement of blood from auricles to the ventricles. The impulses travel from SA node to the Atrioventicular node or AV node. This node helps in delaying the movement of electrical signal from SA node towards the ventricles. This delay helps in the relaxation of ventricles and complete contraction of auricles. The relaxed ventricles accomodate all the blood pumped from the auricles. The signals now travel from the AV node to the bundle of his or bundle fibres where they divide in to two branches that travel to the bottom of heart or the heart apex. From the apex of the heart these signal travel to the walls of the ventricles through numerous fibres called Purkinje fibres. The signal reaching the purkinje fibres allow them to contract thereby resulting in the pumping of blood from ventricles to the aorta. From aorta the blood is pumped to the whole body.

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