Cardiac cycle 1

2. CARDIAC CYCLE
KRISHNA V GANDHI

3. Introduction
• Heart act as a pump.
• 2 separate pump in series:
 Systole: Period of contraction.
 Diastole: Period of relaxation , during
which heart fills with blood.

4. DEFINITION
“The electrical and mechanical cardiac events that
occur from the beginning of one heart beat to
beginning of next are called cardiac cycle”
Normal duration ----- 0.8sec at heart rate of 75
beats/min
60seconds/75beats-----0.8secs
This also includes changes in pressure, blood flow
and volumes in the heart chamber.

5. Diastole and Systole
• Total duration: (opposite) ----reciprocal of heart
rate.
• If normal heart rate is 75beats/min.
one beat = 0.8 sec.
• Heart rate increases ,
Cardiac cycle duration decreases
and vice versa.

6. Phases of Cardiac Cycle

7. • 1. atrial systole------------0.1sec
• 1. ventricular systole------0.3sec
• 2. atrial diastole------------0.7sec
• 2. ventricular diastole-----------0.5sec

9. atrial systole-
• It is seen as the impulses are generated in the SA
node
• Atrial muscles contract and atrial pressure rises
with ventricular pressure following it
• 30ml of blood is moved into ventricles

10. Ventricular systole
• Ventricles get invaded by the excitation process.
• Ventricular contraction begins and ventricular
pressure increases . Atrial pressure very rapidly
causes closure of The AV VALVES .
• THE FIRST HEART SOUND IS PRODUCED
THAT IS S1 SOUND.
• Left ventricular pressure inc. The pressure in
the aorta and the pressure in the right ventricle
inc. the pressure in the pulmonary artery.-----
opening of the semilunar valve.
• Ejection of the blood out of the ventricles

11. STROKE VOLUME :
The amount of blood ejected by each ventricles
per one stroke ----- 70-80 ml.
50 ml remains inside -----end systolic ventricular
blood volume.
CARDIAC OUTPUT :
THE VOLUME OF BLOOD PUMPED FROM EACH
VENTRICLES PER MINUTE
C.O = STROKE VOLUME X HEART RATE
ML/MIN ML/BEAT BEATS/MIN
4900 70 70

12. VENTRICULAR DIASTOLE
• Atrial pressure is sustained due to elastic recoil
of the vessel wall
• Pressure increases in the atrium in comparison
to ventricles
• This result in closure of semilunar valve causing
sharp ( SECOND HEART SOUND ) S2.

13. • The intraventricular pressure continues to drop
rapidly and the ventricular muscle continues to
relax.
• Pressure falls below atrial pressure and results
in opening of A-V VALVE

14. ATRIAL DIASTOLE
• Atrial muscles relax and atrial pressure gradually
increases due to the continuous venous return.

16. Quiescent Period
• All the heart chamber are in diastole (relaxed
state) for a period of 0.4 sec of cardiac cycle

18. 1. What is total
duration of
cardiac cycle?

19. 2. Define cardiac
cycle?

20. 3. What do you
understand by
systole?

21. 4. Enlist the
phases of atrial
cycle with
duration?

22. 5. What is
Quiescent period?

23. 6. What happens
to cardiac cycle if
heart rate
increases?

24. REFERENCES
• Ashalatha P R ,Textbook of anatomy and physiology
for nurses, 2nd edition Jaypee publication 2018
pg 411-412
• Geetha N, Textbook of physiology for nursing
students ,1st edition Jaypeebrothers medical
publication , 2014 , Newdelhi pg 124
• Waugh Anne,ross and wilson,anatomy and
physiology in health and illness ,11th edition
Elesiver publication 2011 Pg 84-85
• Yalayyaswamy N N,anatomy and physiology for
nurses ,3rd edition , CBS publication 2013,
pg 193

25. THANK - YOU
Life is like riding a bicycle, to stay
balance you must keep moving.