Introduction to ArtificiaI Intelligence in Higher Education
the-cardiac-cycle-1-powerpoint.ppt
1. The cardiac cycle
WAL: about the sequence of events in one
heart beat
All
Most
Some
• What are the stages in the cardiac cycle?
• How are the pressures in the
heart related to the different stages
in the cycle?
• How do valves control the flow of blood
through the heart?
8. Definitions
Systole = period of ventricular contraction.
Diastole = period of ventricular relaxation.
NOTE: Normally diastole is longer than
systole.
9. Cardiac cycle
General Principles.
Contraction of the myocardium generates
pressure changes which result in the orderly
movement of blood.
Blood flows from an area of high pressure to an
area of low pressure, unless flow is blocked by
a valve.
Events on the right and left sides of the heart are
the same, but pressures are lower on the right.
10. As a chamber fills with blood, the pressure
is going to rise. When a chamber
contracts, the pressure is going to rise.
Changes in pressure affect whether a
valve is open or closed.
Fluids always move from areas of high
pressure to areas of low pressure.
11. Let us think through the cardiac cycle in
terms of pressure:
As the blood passes into the atria, the
valves are open so most will fall
immediately into the ventricle.
There is a gradual rise in pressure in the
atria until the end of atrial systole when the
blood has moved into the ventricles.
12. The intraventricular pressure rises as the
ventricles fill with blood. This closes the
AV valves.
Contraction of the ventricles means that
the intraventricular pressure is higher than
the pressure in the artery which forces the
blood out of the ventricle and into the aorta
or pulmonary artery (depending on which
side of the heart you’re looking at).
13. The increase in pressure of the artery
causes the closing of the semilunar valves
preventing the back flow of blood into the
ventricle.
16. Atrial systole
The heart is full of blood
and the ventricles are
relaxed
Both the atria contract
and blood passes down
to the ventricles
The atrio-ventricular
valves open due to blood
pressure
70% of the blood flows
passively down to the
ventricles so the atria do
not have to contract a
great amount.
17. Ventricular systole
The atria relax.
The ventricle walls
contract, forcing the
blood out
The pressure of the
blood forces the atrio-
ventricular valves to
shut (producing the
heart sound ‘lub’)
19. Diastole
The ventricles relax
Pressure in the ventricles
falls below that in the
arteries
Blood under high
pressure in the arteries
causes the semi lunar
valves to shut. This
produces the second
heart sound, ‘dub’.
During diastole, all the
muscle in the heart
relaxes.
20. Blood from the vena
cava and pulmonary
veins enter the atria.
The whole cycle
starts again.
21.
22. 5 mins – try it yourself!
Match the letter on the graph to the following
events
Semi-lunar valves open
Atrio-ventricular valves close,
Semi-lunar valves close
Atrio-ventricular valves open
Pressure in
ventricle higher
than in atria – shuts
atrioventricular
valves to prevent
backflow
A
23. Pressure in
ventricle higher
than in atria – shuts
atrioventricular
valves to prevent
backflow
Pressure in
ventricle higher
than in aorta–
opens semi lunar
valves
Pressure in aorta
higher than
ventricles – shuts
semi lunar valves
Pressure in atria
higher than in
ventricles –
atrioventricular
valves open
24. Activities
1. Card sort – put the statements into the
correct order to show the events that
occur during the cardiac cycle.
2. Try the questions on your worksheet.
You may wish to use the textbook to help
you interpret the information on the
graph.