CVS: The Cardiac Cycle Flashcards
Define systole.
Contraction and rejection of blood from the ventricles.
Define diastole.
Relaxation and fill of the ventricles.
Where is the tricuspid valve?
Right side, between the atria and the ventricles
Where is the mitral value found?
The left side, between the atria and the ventricles.
Where is the pulmonary valve found?
The entrance of the pulmonary artery
Where is the aortic valve found?
The entrance if the aorta
Which is under higher pressure, the systemic circulation or pulmonary circulation?
Systemic
What is stroke volume?
The amount of blood each ventricle ejects each beat.
What is the average stroke volume?
70ml blood per beat
What is relatively different about a cardiac action potential?
It’s relatively long, approx 280ms
What anatomical structure prevents inversion of valves on systole?
Attachments called chordae tendinease, which attach the valves to papillary muscles.
Name the 7 stages of the cardiac cycle.
- Atrial Contraction
- Isovolumetric Contraction
- Rapid Ejection
- Reduced Ejection
- Isovolumetric Relaxation
- Rapid Filling
- Reduced Filling
Describe the relative timings of systole and diastole.
Diastole approx 0.55s
Systole approx 0.35s
(At 67 BPM)
How do the relative timings of systole and diastole change during exercise?
Systole remains the same, diastole increases in speed
What is the origin of S1?
The closing of tricuspid valve and the mitral valve.
What is the origin of S2?
The closing of the aortic and pulmonary valves
What is the Wiggers diagram?
Compares changes in pressure with changes in volume, changes in electrochemical properties and with the sounds of the heart
Which side if the heart do wiggers diagrams usually plot? What would be the different if the other side of the heart was to be plotted?
- Left
- Right would be the same but at a lower pressure
In a wiggers diagram, what is one heart beat equivalent to?
One systole and one diastole
What position are the valves in during atrial contraction?
Mitral/ Tricuspid: Open
Aortic/ Pulmonary: Closed
What position are the valves in during Isovolumetric contraction?
Mitral/ Tricuspid: Closed
Aortic/ Pulmonary: Closed
What position are the valves in during Rapid Ejection?
Mitral/ Tricuspid: Closed
Aortic/ Pulmonary: Open
What position are the valves in during Reduced Ejection?
Mitral/ Tricuspid: Closed
Aortic/ Pulmonary: Open
What position are the valves in during Isometric Relaxation?
Mitral/ Tricuspid: Closed
Aortic/ Pulmonary: Closed
What position are the valves in during Rapid Filling?
Mitral/ Tricuspid: Open
Aortic/ Pulmonary: Closed
What position are the valves in during Reduced Ejection?
Mitral/ Tricuspid: Open
Aortic/ Pulmonary: Closed
What are the 2 types of left valve abnormalities?
- Stenosis
2. Regurgitation
What is a stenosis?
When the valve doesn’t open enough
What is regurgitation?
Valve doesn’t close all the way
How does Aortic valve regurgitation affect the function of the heart?
- Blood flows back into LV during diastole. This increases the stroke volume hence systolic pressure increases and diastolic pressure decreases. This results in a bounding pulse leading to head bobbing or Quinke’s sign.
- LV hypertrophy
How does Aortic valve stenosis affect the function of the heart?
- Increased LV pressure -> LV hypertrophy
- Left sided heart failure -> syncope (fainting) and angina
How does mitral valve regurgitation affect the function of the heart?
Increases preload causing LV hypertrophy
How does mitral valve stenosis affect the function of the heart?
- Increase in LA pressure
- Pulmonary oedema ->RV hypertrophy
- LA dilation -> atrial fibrillation or oesophagus compression
How will aortic stenosis affect the heart sounds?
Crescendo-decrescendo murmur
How will aortic valve regurgitation affect the heart sounds?
Early decrescendo diastolic murmur
How will mitral valve stenosis affect the heart sounds?
Snap as valve opens: diastolic rumble
How will mitral valve regurgitation affect the heart sounds?
Holosystolic mumber
Define afterload.
The load the heart must eject blood against (roughly equivalent to aortic pressure)
Define preload.
Amount the ventricles stretched in diastole
Define total peripheral resistance.
Resistance to blood flow offered by all systemic vasculature
Which vessels offer the greatest resistance?
Arterioles
State the frank-Starling law.
The more the heart fills the harder it contracts (up to a limit)
