Flashcards in Cardiac Cycle Deck (26)
How long does an action potential last?
280ms. It is a single contraction.
How do pacemakers work?
They generate one action potential at regular intervals.
What are the two phases of the cardiac cycle?
Systole (each action potential) and diastole (the intervals between the action potentials)
Where is the natural pacemaker?
At the sino atrial node in the wall of the right atrium.
What is the delay of the excitement at the atrio ventricular node?
Describe the events that lead to ventricle contraction.
Signal received by the atrio ventricular node, this spreads the signal down the septum (between the ventricles).
This then spreads through the ventricular myocardium from inner to outer surface. (Endocardial to epicardial).
The ventricle then contracts from the apex up to force the blood up towards the outflow valves.
How frequent does the sino atrial node generate an action potential at rest?
Once a second. This increases during activity.
How long is ventricular systole?
Extra point - is atrial systole longer or shorter?
Ventricular systole is 280ms.
Extra point - atrial systole is shorter.
How long is relaxation in the heart?
What fills the ventricles?
The veins during diastole.
Where do the ventricles pump blood during systole?
Into the arteries for it to go around the whole body. (Or to the lungs if pulmonary artery)
What causes the mitral valve to open and close?
It is open when the atrial pressure is higher than the ventricular pressure.
It is closed when the ventricular pressure is higher than the atrial pressure.
What causes the aortic valve to open and close?
It is open when the intraventricular pressure is higher than the aortic pressure.
It is closed when the aortic pressure is higher than the ventricular pressure.
Starting towards the end if ventricular systole, what is happening at this stage of the cardiac cycle?
The ventricles are contracted with a high intraventricular pressure. Blood is flowing through the outflow valves.
What happens in the cardiac cycle when the ventricles begin to relax?
The intraventricular pressure falls and becomes less than the arterial pressure making the outflow valves close.
Isovolumetric relaxation occurs.
What happens in the cardiac cycle during diastole?
The atrial pressure is higher than the atrial pressure so blood drains into it.
What happens in the cardiac cycle at the beginning of diastole.
The atrioventricular valves open and blood flows to the ventricles because the ventricular pressure is lower than the atrial pressure.
*this is called the rapid filling phase and lasts 200-300ms.*
What happens in the cardiac cycle during diastole.
The ventricles fill more slowly as the ventricular pressure matches the atrial pressure. Then filling stops.
What happens in the cardiac cycle during atrial systole?
A small amount of extra blood is pumped into the ventricles.
What happens in the cardiac cycle during ventricular systole?
Te ventricular pressure rises rapidly and exceeds the atrial pressure. All valves close.
What is the rapid ejection phase?
When the outflow valves open and blood flows into the arteries.
What happens in the cardiac cycle towards the end of systole?
The rate of blood flow falls. Atrial and ventricular pressure peaks and the outflow ceases. (There is still some blood in the ventricle)
What are the 2 main sounds associated with the valves closing?
Lup - closure of the atrioventricular valves.
Dup - closure of the outflow valves.
At which stage in the cardiac cycle would you hear a lup sound?
At onset of the ventricular systole.
At which stage in the cardiac cycle would you hear a dup sound?
At the end if ventricular systole.