Conduction of the heart
Purkinje fibers
located in the apex of the myocardium and the lateral walls of the ventricles; distribute the electrical impulses to the ventricular syncytium and papillary muscles, stimulating them to contract
Atrioventricular (AV) node
What is B?
AV bundle (Bundle of His)
What is C?
Bundle branches
What is D?
Medulla oblongata
contains the center that controls heartbeat and blood vessel activity
Atrial syncytium
A mass of merging cells in the left and right atrium that act as a unit as they contract and relax at the same time; receive impulses from SA node
Ventricular syncytium
A mass of merging cells in the left and right ventricles that act as a unit as they contract and relax at the same time; receive impulses from Purkinje fibers
Atrioventricular (AV) node
A region of specialized heart muscle tissue between the left and right atria where electrical impulses are delayed allowing both atria to contract completely before spreading to the AV bundle; receives impulses from atrial syncytium
Sinoatrial (SA) node
A specialized cardiac muscle tissue located in the back wall of the right atrium; initiates action potentials first and conducts them to the atria; called pacemaker
Atrial systole
Atria contract while ventricles relax; AV valves open and blood enters ventricles; SL valves closed; the first step of cardiac cycle
AV bundle (Bundle of His)
Located between atria and ventricles superior to the interventricular septum; reeives impulses from AV node and conducts them to the bundle branches.
Bundle branches
Located in the interventricular septum; receive impulses from AV bundle and conduct them down to the Purkinje fibers.
Cardiac cycle
Series of myocardial contractions and relaxations that constitutes a complete heartbeat; consists of atrial systole, ventricular systole, and diastole
Atrial diastole
The period of relaxation of the two atria
Ventricular diastole
The period of relaxation of the two ventricles.
Purkinje fibers
What does E point to?
Sinoatrial (SA) node
What is A?
Diastole
relaxation of both atria and ventricles; the third and last step of cardiac cycle
Lubb sound
the first, longer sound of the heartbeat, caused by the closure of AV valves (tricuspid and bicuspid) while ventricles are contracting
Dupp sound
the second, shorter and higher pitched sound of the heartbeat, caused by the closing of the semilunar valves (aortic and pulmonary) as blood is pumped out of the heart
Ventricular systole
ventricles contract while atria relax; A-V valves close as pressure forces valves to snap shut; blood rushes into arteries as SL valves open; the second step in cardiac cycle.