Electrical conduction system of the heart

Sinus node 1 - 2 AV node

Important structures are linked graphics

The conduction system of the heart passes the electrical signals further regulate the pumping action of the heart. However, the basic rhythm of these pulses is generated by the excitation education system. Both systems - excitation education and conduction system - the heart does not consist of nerve, but from specialized heart muscle cells.

Excitation education system

The primary pulse generator ( pacemaker ) of the heart's sinus node serves. The sinus node generates electrical impulses. On the basis of the position of the sine - knot in the wall of the right atrium at the entry point of the superior vena cava, the electric excitation, and thus the contraction of the muscle of the right atrium is made ​​. Per minute walk from the sinus node from about 60 to 80 excitations.

The secondary pacemaker of the heart is the atrioventricular node or short AV node. In case of failure of the sinus node, the AV node can take over the pulsing as a secondary pacemaker. The AV node itself can " produce " 40 to 50 impulses per minute. Since this frequency is exceeded, however, in the healthy heart of the sinus node, its pacemaker activity is not used. In a so-called AV block in which the reconciliation through the AV node is partially or completely disrupted, the AV node acts as the pacemaker of the heart.

In principle, each heart muscle cell, the possibility of impulse formation ( automaticity ).

Cardiac Conduction System

The excitations are forwarded by the His- Purkinje system. First they get from the AV node on to the His bundle ( after Wilhelm His). Also, the His bundle has an intrinsic rhythm and can initialize 20 to 30 excitations per minute. Thus, the His bundle Make tertiary pacemaker of the heart a backup feature for the AV node.

The common trunk of the His bundle ( trunk fasciculi atrioventricularis ) is divided into three " branches " on: Two left and a right bundle branch (after Sunao Tawara ). If the excitation line is interrupted in one of the legs, it is called a bundle branch block ( right or left bundle branch block ). The legs split at the apex further in Purkinje fibers ( afterJan Evangelista Purkinje ), which represent the last Leitstrecken the conduction system and come into contact with the heart muscle working muscles. From the histological point of view the rich Glykogenvorkommen in the cells of Purkinje fibers are worth mentioning. In addition, can be under the plasma membrane a few myofibrils prove.

Distinction between: stimulus and arousal

A stimulus ( for example heat, pressure, pain, etc. ) is an external force, which is received, for example, in the skin by the sense cells ( receptors). An irritant effect on the postsynaptic nerve cells, the formation of electrical pulses, which are referred to as excitation. For impulse formation in the heart and the excitement forwarding through the fibers of the conduction system but no appeal is necessary. There are (not the stimulus itself) forwarded by the fibers only the electrical impulses.