2. • The heart is hollow organ. One septum divides the heart into
two chambers. The left cardiac chamber discharges blood
received from the pulmonary circulation. This blood is
discharges out through the aorta to the systemic circulation.
The right heart chamber discharges blood received from the
systemic circulation. This blood is discharges to the lungs
through the pulmonary arteries.
3. • Physiologists have determined that in the adult the heart makes
from 60-72 beats per minute.
4. • Each beat of the heart is followed by a period of rest for the
cardiac muscle. Each wave of contraction and a period of rest
following it compose a cardiac cycle.
a) Auricular systole
b) Ventricular systole
c) Joint diastole
5. • Each cardiac cycle consist of three phases: physiologists have
called the first phase of short contraction of both atria- the
atrial systole. The second phase of a more prolonged
contraction a both ventricles-the ventricular systole. The period
of rest of the cardiac muscle is called the diastole.
6. • This phase involves the contraction of the 2 auricles,
pushing the blood into the respective ventricles. There is
no back flow of blood due to the presence of the bicuspid
and the tricuspid valves. The atrial systole takes 0.1
second. This is followed by the atrial diastole when both
the auricles relax simultaneously. This is about 0.7
seconds.
Auricular Systole (Atrial
Systole)
7.
8. • Ventricular systole is followed by ventricular diastole. The auricles
are already in diastole, so all the chambers of the heart are in diastole.
• When the ventricles are in diastole, the pressure in the ventricles
decreases more than that in the great arteries. So to prevent the
backward flow of blood, the semilunar valves close rapidly. This
produces the second heart sound called dup.
• During a complete cardiac diastole, blood from the superior and
inferior vena cava flows into the auricles slowly. The pressure in the
ventricles decreases and finally becomes lower than atrial pressure.
Then the AV values open and blood from the atria starts entering into
the relaxing ventricles. A complete cardiac diastole takes only 0.4
seconds.
Joint Diastole.
9. • The left ventricle discharges out the blood received by the left
atrium from the pulmonary circulation through the aorta to
the systemic circulation.
10. • The blood received from the systemic circulation by the right
atrium is discharged out of the right ventricle to the lungs
through the pulmonary arteries.
