Bundle of His
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The bundle of His (BH) or His bundle (HB) ( "hiss"
Medical Terminology for Health Professions, Spiral bound Version
'. Cengage Learning; 2016. . pp. 129–.
) is a collection of heart muscle cells specialized for
electrical conduction Electrical resistivity (also called specific electrical resistance or volume resistivity) is a fundamental property of a material that measures how strongly it resists electric current. A low resistivity indicates a material that readily allows ...
. As part of the
electrical conduction system of the heart The cardiac conduction system (CCS) (also called the electrical conduction system of the heart) transmits the Cardiac action potential, signals generated by the sinoatrial node – the heart's Cardiac pacemaker, pacemaker, to cause the heart mus ...
, it transmits the electrical impulses from the atrioventricular node (located between the atria and the ventricles) to the point of the apex of the fascicular branches via the bundle branches. The fascicular branches then lead to the Purkinje fibers, which provide electrical conduction to the ventricles, causing the
cardiac muscle Cardiac muscle (also called heart muscle, myocardium, cardiomyocytes and cardiac myocytes) is one of three types of vertebrate Muscle tissue, muscle tissues, with the other two being skeletal muscle and smooth muscle. It is an involuntary, striat ...
of the ventricles to
contract A contract is a legally enforceable agreement between two or more Party (law), parties that creates, defines, and governs mutual rights and obligations between them. A contract typically involves the transfer of goods, Service (economics), ser ...
at a paced interval.


Function

The bundle of His is an important part of the
electrical conduction system of the heart The cardiac conduction system (CCS) (also called the electrical conduction system of the heart) transmits the Cardiac action potential, signals generated by the sinoatrial node – the heart's Cardiac pacemaker, pacemaker, to cause the heart mus ...
, as it transmits impulses from the atrioventricular node, located at the anterior-inferior end of the interatrial septum, to the ventricles of the heart. The bundle of His branches into the left and the right bundle branches, which run along the interventricular septum. The left bundle branch further divides into the left anterior fascicle and the left posterior fascicle. These bundles and fascicles give rise to thin filaments known as Purkinje fibers. These fibers distribute the impulse to the ventricular muscle. The ventricular conduction system comprises the bundle branches and the Purkinje networks. It takes about 0.03–0.04 seconds for the impulse to travel from the bundle of His to the ventricular muscle.


Clinical significance

Disorders affecting the
cardiomyocyte Cardiac muscle (also called heart muscle, myocardium, cardiomyocytes and cardiac myocytes) is one of three types of vertebrate Muscle tissue, muscle tissues, with the other two being skeletal muscle and smooth muscle. It is an involuntary, striat ...
s that make up the electrical conduction system of the heart are called heart blocks. Heart blocks are separated into different categories based on the location of the cellular damage. Damage to any of the conducting cells in or below the bundle of His is collectively referred to as "infra-Hisian blocks". To be specific, blocks that occur in the right or left bundle branches are called " bundle branch blocks", and those that occur in either the left anterior or the left posterior fascicles are called "fascicular blocks", or "hemiblocks". The conditions in which both the right bundle branch and either the left anterior fascicle or the left posterior fascicle are blocked are collectively referred to as bifascicular blocks, and the condition in which the right bundle branch, the left anterior fascicle, and the left posterior fascicle are blocked is called trifascicular block. Infra-hisian blocks limit the heart's ability to coordinate the activities of the atria and ventricles, which usually results in a decrease in its efficiency in pumping blood.


Pacing

A 2000 study found that direct His bundle pacing is more effective in producing synchronized ventricular contraction—and therefore in improving cardiac function—than apical pacing.


Etymology

These specialized muscle fibers in the heart were named after the
Swiss Swiss may refer to: * the adjectival form of Switzerland *Swiss people Places *Swiss, Missouri *Swiss, North Carolina *Swiss, West Virginia *Swiss, Wisconsin Other uses *Swiss-system tournament, in various games and sports *Swiss International A ...
cardiologist Cardiology () is a branch of medicine that deals with disorders of the heart and the cardiovascular system. The field includes medical diagnosis and treatment of congenital heart defects, coronary artery disease, heart failure, valvular heart d ...
Wilhelm His Jr., who discovered them in 1893.


See also

* Atrioventricular node * Bachmann's bundle * Bundle branches * Bundle of Kent * Purkinje Fibers *
Sinoatrial node The sinoatrial node (also known as the sinuatrial node, SA node or sinus node) is an ellipse, oval shaped region of special cardiac muscle in the upper back wall of the right atrium made up of Cell (biology), cells known as pacemaker cells. The s ...


References


Further reading

* * * *


External links

* – "Right atrioventricular bundle branch, anterior view" * ()
Healthy Heart
{{Authority control Cardiac anatomy Cardiac electrophysiology