SYSTOLE
Systole is the name used when there is
a contraction of one of the chambers. The blood enters a relaxed
heart, this is when the atria begins to contract, known as atrial
systole. This contraction forces the blood from the atria into the
ventricles. The valves stay the same until the space within the
ventricle is full. This causes the ventricle to get smaller, which
in turn squeezes the blood, this is known as “blood pressure”. So,
as the blood pressure starts to rise the A-V shuts tight. The sound
of our hearts beating is one of these valves closing. The first
sound is the “lubb”, the A-V slamming shut, the second part of the
heart beat is the semilunar valve slamming shut, this makes the
“dupp”. When the ventricles contract not only do the A-V shut, but
the semilunar valves are forced open. From here the blood flows from
either the pulmonary trunk (from right ventricle) or the aorta (the
left ventricle).
DIASTOLE
The sequence that follows the
contraction of both the atrial systole then ventricular is
relaxation, better known as diastole. After the ventricles have
started to contract the atria begins to relax, this is called atrial
diastole. Then, after the blood has left the ventricles the
ventricular diastole begins. The semilunar valves close as the
ventricles start to relax. When they are relaxed the A-V valves
open, and so the sequence starts all over again.
To be more precise with systole and
diastole in the sequence of events, there is a certain cycle.
This is atrial systole, followed by
atrial diastole.
Ventricular systole, followed by
ventricular diastole.
