Monday, 4 June 2012

- Conductive system of the Heart.

Conductive system of the Heart.

The Function of the heart is to contract rhythmically and pump blood to the lungs for oxygenation and then to pump this oxygenated blood into the general (systemic) circulation.

The signal for cardiac contraction is the spread of electrical currents through the heart muscle.
In normal Conditions, these electrical currents are produced by  pacemaker cells of the Sinoatrial node (SAN), located on top of the right atrium near the opening of the superior vena cava at a rate of 100 per minute.

 These impulses move down through fibers in the myocardial wall and come together in the atrioventricular junction  where they are slowed down before entering and stimulating the controlled contraction of the muscles surrounding the two ventricles.

 The AV Junction is similar to a wire or cable connecting the atria and the ventricles and is responsible for sending electrical impulses from the atria to the ventricles it is located at the base of interatrial septum and extends to the inter-ventricular septum.

The proximal part of the AV junction is called AV node while the distal  part of the AV junction is called Bundle of His.

Bundle of his splits into 2 branches called the right and left bundle branch which allows the even spread of the electrical signal to both ventricular myocarduim  simultaneously through purkinje fibers .

The conduction is slowest through the AVN and fastest through  purkinje fibers.
The relatively slow conduction speed through AVN allows the ventricles to fill with blood before contraction.

Automaticity refers to the capcity of certain cardiac muscle cells to function as a pacemakers by spontaneously generating electrical impulses (e.g SAN, atria,AVN, ventricles)

  1. clinical electrocardiography a simplified approach 7th ed,Ary L.Goldberger, CH1,P.g 3,4,5.

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