Cardiac cycle
The heart is a pump that requires two actions for its proper functioning: a
contraction (or systole) and a relaxation (diastole). These two events are part of
the cardiac cycle. The direction of blood circulation in the heart is ensured by the
presence of valves, it only occurs from the atria to the ventricles and from the
ventricles to the major arteries.
Isovolumetric contraction
The isovolumetric contraction is the phase where the ventricles are full of blood
and have begun to contract, increasing the pressure within (right after diastole).
Since in this phase the ventricular pressure exceeds the atrial pressure (P
ventricle> P atria) the atrioventricular valves (tricuspid and mitral valves) close.
The amount of blood in the ventricles before the heart contracts (right at the
end of diastol) is called the end-diastolic volume (EDV).
The closure of the atrioventricular valves makes the S1 sound.
The pressure increase in the ventricles causes a slight swelling of the
atrioventricular valves, leading to a small increase in the atrial pressure
represented by the 'c' wave in the diagram.
Ejection (Isotonic contraction)
The blood contained in the ventricles is forcefully ejected first rapidly, then at a
decreasing rate as the amount of blood to be ejected lessens.
Rapid ejection
The ventricular pressure becomes higher than the arterial (pulmonary
artery/aorta) pressure (P ventricle> P artery) leading the semilunar valves
(pulmonary and aortic valves) to open, then there is a rapid ejection of blood due
to increased ventricular contractility. Approximately, 70% of the blood vloume is
being ejected in this phase.
Cardiac cycle 1
The heart is a pump that requires two actions for its proper functioning: a
contraction (or systole) and a relaxation (diastole). These two events are part of
the cardiac cycle. The direction of blood circulation in the heart is ensured by the
presence of valves, it only occurs from the atria to the ventricles and from the
ventricles to the major arteries.
Isovolumetric contraction
The isovolumetric contraction is the phase where the ventricles are full of blood
and have begun to contract, increasing the pressure within (right after diastole).
Since in this phase the ventricular pressure exceeds the atrial pressure (P
ventricle> P atria) the atrioventricular valves (tricuspid and mitral valves) close.
The amount of blood in the ventricles before the heart contracts (right at the
end of diastol) is called the end-diastolic volume (EDV).
The closure of the atrioventricular valves makes the S1 sound.
The pressure increase in the ventricles causes a slight swelling of the
atrioventricular valves, leading to a small increase in the atrial pressure
represented by the 'c' wave in the diagram.
Ejection (Isotonic contraction)
The blood contained in the ventricles is forcefully ejected first rapidly, then at a
decreasing rate as the amount of blood to be ejected lessens.
Rapid ejection
The ventricular pressure becomes higher than the arterial (pulmonary
artery/aorta) pressure (P ventricle> P artery) leading the semilunar valves
(pulmonary and aortic valves) to open, then there is a rapid ejection of blood due
to increased ventricular contractility. Approximately, 70% of the blood vloume is
being ejected in this phase.
Cardiac cycle 1
