L03: Cardiac Cycle Flashcards
What is the equation for atrial blood pressure
Stoke volume x heart rate x total peripheral resistance
What activity does the electrical activity of the heart stimulate
Mechanical activity
What does mechanical activity cause
Pressure and volume change
What is the cardiac cycle
The coordinated series of pressure and volume changes in the heart
What does the cardiac cycle result in
Ejection of a volume of blood from the ventricles
What is the ejection of blood form the ventricles known as
Stroke volume
Which 2 clinical cases can affect the cardiac cycle
Myocardial infarction
Valve defect
What happens to the cardiac cycle length when the heart rate increases
Decreases
What are the 2 phases of the cardiac cycle
Diastole
Systole
Which stage occupies the most of the cardiac cycle
Diastole
What are the 5 principles of the cardiac cycle
- Contraction of the muscles around chamber increase the pressure
- Valves open when there is a pressure energy gradient across them (greater in atrium than ventricles)
- blood flows down a pressure gradient
- when valves open pressure in neighbouring chamber change
- when valves close pressure in neighbouring valves can be different
Is the pattern of the pressure change same on both sides of the heart (right and left side)
Yes
Do valves on the right and left side of the heart open and close at the same time in the same way ?
Yes
What are the phases of the cardiac cycle
1) ventricular diastole: rapid filling
2) ventricular diastole, atrial systole and ventricular filling
3) ventricular systole: isovolumetric contraction
4) ventricular systole : ejection
5) ventricular diastole: isovolumetric relaxation
And this goes back to first step of the ventricular diastole: rapid filling to repeat the cardiac cycle
Top tip for remembering the phases of the cardiac cycle
The phase of the cardiac cycle mostly refers to the ventricles and their state e.g ventricular diastole and ventricular systole
What are the valves present in the left heart
Mitral valve
Aortic valve
What are the valves called in the right heart
Tricuspid valve
Pulmonary valve
In terms of the left side of the heart what happens at the phase of ventricular diastole (rapid filling)
1) pulmonary vein has greater pressure than the atrial pressure
2) mitral valve is open because the atrial pressure is greater than the ventricular pressure
3) ventricles fill with blood
4) aortic valve is closed because the ventricular pressure is lower than the aortic pressure
Describe what happens at the ventricular diastole, atrial systole, ventricular filling phase
1) atrial depolarisation leads to atrial contraction so there is an increase in atrial pressure
2) increase in atrial pressure leads to blood flowing into ventricles (ventricles are at rest)
Describe what happens at the ventricular systole, isovolumetric contraction phase
1) the ventricles contact so ventricular pressure increase
2) as ventricular walls are thick there is a greater increase in pressure in the ventricles
3) ventricular pressure is greater than the atrial pressure so mitral valves close
4) ventricular pressure is still smaller than the aortic pressure so aortic valve is also closed
5) as both valves are closed volume of blood remaining in the ventricles is the same = isovolumetric contraction
6) continuing ventricular contraction causes the pressure to increase in ventricles which is greater than the aortic pressure
7) blood ejects out into the aorta
8) aortic pressure is greater than the ventricular pressure as ejection continues
Describe what happens in the ventricular diastole, isovolumetric relaxation
1) ventricle repolarisation occurs so the ventricles relax and ventricular pressure decreases
2) aortic valve closes as ventricle pressure is smaller than aortic pressure
3) ventricular pressure is greater than the atrial pressure so mitral valve closes
4) both valves are closed so volume of blood in the ventricles remain the same= isovolumetric relaxation
What does the lub sound of the heart represent
Mitral valve and tricuspid valve close
What does the dub sound of the heart represent
Pulmonary and aortic valve close
Why does the atrial pressure change slight during contraction
Atrial wall muscles are thin
Which side of the heart has a lower pressure
Right side
Why does the right side of the heart have a general lower pressure
Pulmonary resistance is lower so a lower pressure is required to overcome the smaller resistance
Why does the left side of the heart have a higher pressure
Systemic resistance is high so the left side needs a higher pressure to overcome the higher pressure to drive blood flow out.
