We use the ADAM CD on the Cardiovascular System to explore the anatomy of the heart, the intrinsic conduction system, cardiac action potential, the events of the cardiac cycle, and cardiac output.

I. Anatomy: Here is a graphic illustrating the 4 heart chambers (right and left atria and right and left ventricles), the 4 heart valves (tricuspid, pulmonary semilunar valve, mitral or bicuspid and aortic semilunar valve), the coronary arteries and the chordae tendineae:

Also, here is the circuit of blood flow:

II. Intrinsic Conduction System: The intrinsic conduction system is responsible for the initiation and coordination of the heart beat. The pathway of depolarization is as follows: Sino-atrial (SA)node to the atrioventricular (AV) node via the internodal pathway, from the AV node through the bundle branches to the Purkinje fibers. The pathway of depolarization gives us an EKG reading:

III. Cardiac Action Potential: The coordinated contraction of the heart results from electrical changes that take place in the cardiac cells. Autorhythmic cells generate an AP, triggering the contraction of the contractile cells. The waves of depolarization spread from the branched cardiac cells to branched cardiac cells via gap junctions. The membrane potential of the contractile cells reach a threshold and in turn generate an AP. The cells depolarize, contract, repolarize then relax.

IV. Cardiac Cycle: All events related to the flow of blood through the heart during one complete heartbeat is the cardiac cycle. There are 3 phases of the cardiac cycle:

1-Ventricular Filling (Mid-to-late Ventricular Diastole): blood flows passively into the atria through open atrioventricular valves and into ventricles, where pressure is lower. The atria contract, forcing remaining blood into ventricles.

2-Ventricular Systole: Ventricles contract and intraventricular pressure rises, closing the atrioventricular valves. Briefly, the ventricles are completely closed chambers (Isoventricular contraction). Rising ventricular pressure forces semilunar valves open and blood is ejected from the heart (Ventricular ejection).

3-Isovolumetric Relaxation: Ventricles relax and ventricular pressure drops. Blood backflows, closing the semilunar valves. Ventricles are totally closed off again. Meanwhile, the atria have been filling with blood. When atrial pressure exceeds ventricular pressure, atrioventricular valves open and ventricular filling, phase 1, begins again.

V. Cardiac Output: The cardiac output is the amount of blood pumped out by each ventricle in 1 minute; it can be increased markedly to meet demands we put on our body.

Resting Values:

CO: 5.25 L/min = 75 beats/min X 70mL/beat