Download The Cardiac Cycle

The Cardiac Cycle
The Cardiac Cycle
The simultaneous contraction of both atria
followed by both ventricles.
 The cardiac cycle is all of the physiological
process that are used to carry out the functions
of the cardiovascular system.
 Heart Sounds of the Cardiac Cycle

– The rhythm of the heart (lub-dup, pause, lub-dup,
pause, lub-dup…)
 Lub: sound of the Av valves closing during
ventricle contraction.
 Dup: The sound of the semi-lunar valves during
ventricle relaxation.
Heart Conduction System
The heart contains specialized cells that send
electrical impulse to cardiac muscle cells.
 The rhythm of the heart (heartbeat) is controlled
by pace-setting (pace maker) cells that control
those electrical impulses.
 Those electrical impulses are what stimulate the
series of muscle contractions within the atria
and ventricles to push blood throughout the
system.

The Cardiac Cycle
The impulses follow a specific pathway in order
for the cycle to occur properly
 Sinoatrial (SA) node (pacemaker): Begin each
cardiac cycle, initiates atrial contraction, then
stimulates AV node.
 Atrio-ventricular (AV) node: Sends the
impulse down the AV bundle (bundle of His):

conducting fibers that run to the apex of the
heart, the impulse then reaches the Purkinje
Fibers (in ventricle wall), which results in
rhythmic ventricle contraction.
The Cardiac Cycle
Stroke Volume: The volume of blood
pumped out of the heart by one ventricle
(can be either one) per heartbeat.
 Cardiac Output: The volume of blood
pumper out of the heart by the ventricles
in a given period of time. (usually
expressed as liters per minute)

Blood Pressure (Bp)
Is the force exerted by blood against the
inner walls of vessels.
 Given as two numbers in (mm Hg).
 First number represents systolic pressure
(heart muscle contraction).
 Second number represents diastolic
pressure (resting period between
contractions).
 Systolic/diastolic ( Example: 120/80).

Factors that Influence Blood
Pressure
Blood Volume: Amount of blood
occupying the space with the blood
vessels (Hemorrhage).
 Peripheral Resistance: Diameter of
vessels, vasoconstriction, vasodilatation.
