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1. CARDIAC CYCLE

2. The Cardiac Cycle
Sequence of events that makes up one heart beat
Has two basic components:
►(1) a contraction phase (systole) during which blood is
ejected from the heart
►(2) a relaxation phase (diastole) during which the chambers
of the heart are filled with blood.

4. Cardiac cycle-
Three phases:
Atrial systole
Ventricular systole
Ventricular diastole.
Diastole- relax systole- contract

5. Cardiac cycle- Atrial Systole
Heart is filled with blood.
Both atria contracts.
Blood flows from the atria into the ventricles.
valves in the ventricles prevents the back flow of
blood into the atria.

6. Cardiac cycle- Atrial Systole

7. Cardiac cycle- Ventricular Systole
Muscles in ventricles contract in different ways/fibres
contract
Pressure increases in ventricles
Atrio-ventricular valves close to prevent back flow of
blood
Ventricular pressure exceeds aortic pressure or pressure
in pulmonary artery, semilunar valves open

8. Cardiac cycle- Ventricular Systole
Blood flows into the arteries
Pressure decreases in ventricles
When pressure in ventricles decreases/becomes less than
in arteries, semilunar valves close
Pressure in ventricles becomes less than atria,
atrioventricular valves open

9. Cardiac cycle- Ventricular Systole
 Ventricular systole last for about 0.3 s.

10. Cardiac cycle- Ventricular systole
 Atria and ventricles relax.

11. Blood Pressure
Blood pressure is how hard the heart is working to
pump blood around the body
OR
The force developed by blood pushing against the
walls of blood vessels.

12. Blood Pressure
Sphygmomanometer- measures the pressure
in a large artery close to the elbow joint.
Measures both Systolic and diastolic pressure.

13. Blood Pressure
Systolic pressure- maximum pressure produced
as a result of contraction of the left ventricle of the
heart.
Diastolic pressure- lowest pressure produced by
the relaxation of the ventricular muscle in the heart.

14. Blood Pressure
120 mm Hg or kPa is the SI unit.
mmHg- ‘millimetres of mercury’. Refers to the
distance which mercury is pushed up the arm
of a U-tube when a sphygmomanometer is
used.

15. Blood Pressure
Influenced by three factors:
Volume of blood pumped by the heart; blood
pressure increases if stroke volume increases.
Volume of blood in the blood vessels; blood
pressure is high if there is plenty of blood in blood
vessels. It falls if there is blood loss or more blow flows
into capillaries.

16. Blood Pressure
Elasticity of the arteries; blood pressure rises if
the arteries become less elastic or harden. Happens
with age or some diseases.

17. Factors affecting Blood Pressure
Heart rate
 Stroke volume
Age – arteries lose elasticity hence more resistance
to flow
Exercise – can cause an increase in heart rate and
stroke volume.
Strength of the heart beat

18. Factors affecting Blood Pressure
Resistance to flow of blood due to narrowing of
blood vessels/plaque
Smoking – effect of nicotine on arterioles and
adrenal glands/narrowing of arterioles and release of
adrenaline
 Excitement – increase in adrenaline production
which stimulates SAN

19. Relationship between Pulse and Heart Rate
Your pulse is the rate at which your heart beats.
As your heart pumps blood through your body, you can feel a
throbbing in some of the arteries close to the skin's surface.
The two arteries that are easiest to use for taking your pulse
are the:
Radial artery, located on the palm side of your wrist in line
with your thumb.
Carotid artery, located on either side of the windpipe in your
neck.