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cardiac cycle

includes all of the events occurring in the heart during one single heartbeat

systole and diastole

each chamber of the heart goes through these two phases during the cardiac cycle


is when both the atria and ventricles contract and empty of blood


the relaxation phase of the heart during which the chambers are refilling with blood


records both the intensity and the actual time it takes for each part of the cardiac cycle to occur

EKG measures

electrical conductive impulses of the heart muscle and allows physicians to see any disturbances or disruptions in normal heart activity

sinoatrial (SA) node

is the main part of the system that specialized electrical conduction system of the hear initiates each heartbeat

60 to 100 times per minute

the SA node controls the rate of the heart contraction by initiating electrical impulses up to

contraction almost simultaneously

each cardiac cycle or heartbeat starts with the SA node generating an electrical impulse that travels in a wavelike pattern across the cardiac muscle of the atria causing the muscles to

atrioventricular (AV) node

the SA node stimulates this electrical impulse of the ___________ which is located in the posterior, superior portion of the right atrial septal wall, at this point allows the atria to empty completely

bundle of His

the electrical impulse is then transmitted to a special group of conduction fibers which are located in the upper part of the interventricular septal wall

right bundle branch

carries impulses to the right ventricle

left bundle branch

carries impulses to the left ventricle

purkinje fibers

the right and left bundle of branches divide into smaller and smaller branches, ending in the ____________ which spread across the apex of the heart and through the myocardium, stimulating ventricular contraction

ventricles contract

in a twisting sort of action, forcing the blood out of the chambers and into the pulmonary artery on the right side of the heart and the aorta on the left side of the heart

normal sinus rhythm (NSR)

refers to a regular heart rate that falls within the average range of 60 to 80 beats per minute (beats/min)

sinus bradycardia

referrers to a heart rate less than 60 beats/min

sinus tackycardia

referrers to a heart rate greater than 100 beats/min


in both sinus bradycardia and tackycardia the heart rhythm remains even but the rate is


an irregular cardiac rhythm, in which certain conditions interrupt the conduction pathway, SA node to the AV node to bundle of His to right and left bundle branches

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