Question

Describe the origin of the cardiac contraction signal and the pathway it follows through the heart.

Answer 1

• Human heart has four chambers which include 2 atria and 2 ventricles.
• Atria are attached to the ventricles by atrioventricular septum.
• Usually the contraction begins in the upper atria and then spreads on to the ventricles.
• Cardiac muscle or myocardium is an involuntary muscle. This cardiac muscle should undergo contraction in order to pump the oxygenated blood from the heart to peripheral organs through arteries.
• The signal for cardiac muscle contraction begins in the SINO ATRIAL NODE (SA node). This SA node is located in the wall of right atrium.
• Initially when the signal is generated from SA node the atria will contarct then the singal is transfered to AV node also called as ATRIO VENTRICULAR node which lies near atrioventricular septum.
• From AV node the signal spreads to Bundle of His which is located in the interventricular septum and has right & left bracnches.
• From Bundle of His the signal will get transffered on to the purkinje fibers. These purkinje fibres are located in both ventricles in the subendocardial layer of the heart.

SA NODE

↓

AV NODE

↓

BUNDLE OF HIS

↓

PURKINJE FIBERS