The Cardiac Cycle Flashcards
What are the stages of the cardiac cycle
Stage 1 – Atrial Diastole
Stage 2 - Ventricular Diastole
Stage 3 – Atrial Systole
Stage 4 – Ventricular Systole
What does systole mean?
contraction of the heart muscle / when the heart pumps the blood.
What does diastole mean?
relaxation of the heart muscle / when the heart fills with blood.
What happens in atrial diastole stage?
Atria fill with blood
Atrioventricular valves closed.
Semi-lunar valves open
What happens in Ventricular diastole stage?
Rising pressure in atria causes the AV valves to open and ventricles to fill
AV valves open.
Semi-lunar valves closed
What happens in atrial systole stage?
Atria contract, forcing blood into ventricles
AV valves open
Semi-lunar valves closed
What happens in Ventricular systole stage?
Ventricles contract, increasing pressure in the ventricles and forcing blood into the aorta and pulmonary artery
AV valves are forced to close
What are the phases?
Filling phase
Isovolumetric contraction
Outflow phase
Isovolumetric relaxation
What happens in the filling phase?
the ventricles fill during diastole and atrial systole
What happens in the Isovolumetric contraction phase
the ventricles contract, building up pressure ready to pump blood into the aorta.
What happens in the Outflow phase?
the ventricles continue to contract, pushing blood into the aorta and the pulmonary trunk. Also known as systole
What happens in the Isovolumetric relaxation phase
the ventricles relax, ready to re-fill with blood in the next filling phase.
How do you work out the cardiac output?
Cardiac output = heart rate x stroke volume
What is stroke volume?
The amount of blood pumped by the left ventricle of the heart in one contraction
The normal range is 50 to 100 ml.
What is the heart`s pacemaker and how does it work?
The sinus node is an area of specialized cells in the upper right chamber of the heart
It sends an electrical impulse to make your heartbeat. The job of a pacemaker is to artificially take over the role of your sinus node if it isn’t working properly.
What is an ECG
An ECG is a simple test that can be used to check your heart’s rhythm and electrical activity.
Electrodes are placed on your chest to record your heart’s electrical signals.
What does wave P show?
Atrial systole
Excitation of atria so they contract
What does wave QRS show?
Ventricular systole
Excitation of ventricles so they contract
What does wave T show?
Diastole
When the heart chambers are relaxing.
What are the atria
2 top chambers of the heart
What is the ventricle?
2 bottom chambers of the heart
What is the Sinoatrial node (SAN)?
A patch of tissue in the right atrium that generates the electrical activity and initiates a wave of excitation at regular intervals.
What is the Atrioventricular node (AVN)
A patch of tissue found at the top of the septum that picks up the wave of excitation from the atria.
What is the Septum?
The dividing wall between the right and left sides of the heart – prevents mixing of blood.
What is the Bundle of His
A collection of heart muscle cells specialised for electrical conduction.
What are the Purkinje fibres
Specialised conducting fibres found in the heart.
