excitation of the heart and ECG Flashcards
Sinoatrial Node
Primary pacemaker of heart, located in wall of RA; fastest of all auto-rhythmic cells
Atrioventricular Node
Located in interatrial septum above tricuspid valve; delays impulse for 0.1 sec to allow for atrial contraction
Bundle His
Neurological fibers extending from the AV node to the right and left bundle branches that fire the impulse from the AV node to the Purkinje fibers; Located superior to interventricular septum
Right Bundle Branch
Extends toward the apex of the heart and then radiates across the inner surface of the right ventricle
Left Bundle Branch
Extends toward the apex of the heart and then radiates across the inner surface of the left ventricle
Purkinje Fibers
Fibers in the ventricles that transmit impulses to the right and left ventricles, causing them to contract
Electrocardiography
Using electrocardiograph to record electrical currents generated by the heart by measuring voltage differences between leads
P Wave
Depolarization of atria from SA node; lasts 0.08 sec
QRS Complex
Depolarization of ventricles lasts 0.08 sec
T Wave
Repolarization of ventricles lasts 0.16 sec
Lubb
Closing of AV valves; beginning of ventricular contraction
Dubb
Closing of SL valves; beginning of ventricular relaxation
Isovolumetric Contraction
Refers to the short period during ventricular systole when the ventricles are completely closed chambers
Ventricular Ejection
As ventricular pressure rises and exceeds pressure in the arteries, the semilunar valves open and blood is ejected
Cardiac Output
Amount of blood ejected by each ventricle per minute; heart rate x stroke volume
