The Cardiac Cycle Flashcards
Define late diastole.
Both sets of chambers of the heart are relaxed and the ventricles are filling with blood.
What happens when the ventricles are filled with blood and the pacemaker cells reach threshold?
Depolarisation spreads through the atria leading to atrial contraction.
What happens in atrial systole?
Arterial contraction forces a small amount of additional blood into the ventricle.
Describe the pressure in the stage of atrial systole.
The pressure in the atria exceeds the pressure in the ventricles
What does the greater pressure in the atria lead to?
Causes the mitral and tricuspid valves to open.
What happens when the ventricles depolarise and contract?
Pulls the mitral and tricuspid valves shut.
What happens during the isovolumic ventricular contraction/the isometric contraction phase?
Left ventricular pressure to rise above atrial pressure, which closes the mitral valve and produces the first heart sound
What happens to the volume of blood in the isovolumic ventricular contraction/ isometric contraction phase?
Stays the same as the blood has nowhere to go as all the valves are shut
What happens to the ventricular pressure when all the valves are closed?
Ventricular pressure builds up until the pressure exceeds the pressure in the aorta and the pulmonary trunk, causing the aortic and pulmonary valves to open.
What happens in the ventricular ejection phase?
Blood is pumped out of the ventricle and into the aorta and pulmonary trunk
What happens to ventricular pressure as blood is pumped out?
Ventricular pressure drops
What happens when the ventricular pressure decreases beyond the pressure in the aorta and pulmonary trunk?
Aortic and pulmonary valves are pushed closed
What happens in the isovolumic ventricular relaxation phase?
Entry and exit valves are shut
Blood cannot leave
What happens as the atria begin to fill with blood?
Atrial pressure increases and gradually increases beyond ventricular pressure which pushes the mitral and tricuspid valves open and blood flows to the ventricles
Name the two divisions of the cycle.
Diastole and systole
What is the diastole stage known as?
Filling phase
What is the systole phase known as?
Ejection phase
At which point in the cardiac cycle is the systolic pressure?
Maximum pressure in the aorta
At which point in the cardiac cycle in the diastolic pressure?
Minimum pressure in the aorta during diastole
What is pulse pressure?
The difference between systolic and dystopic pressure
(systolic-dystolic)
What is MAP?
Mean arterial pressure
What value is MAP usually measured as?
One third between the diastolic and systolic pressures because two thirds are spent in diastole and one third of the cycle is spent in systole.
Rough estimate
How much of the cardiac cycle is spent in systole?
1/3
How much of the cycle is spent is diastole?
2/3
What are the three increases in pressure in the left atrium?
A wave
C wave
V wave
What is the a wave caused by?
Atrial contraction
What causes the c wave?
When the left ventricle contracts, pressure increases.
It exceeds pressure in the left atria and causes mitral valve to close.
Mitral valve is thin and can bulge into the left atrium, increasing pressure in the left atrium.
What causes the v wave?
The V wave is caused by the relaxation of the right atrium whilst the tricuspid valve is still closed.
What name is given to the volume at the end of diastole?
End diastolic volume (EDV)
What name is given to the volume at the end of systole?
End systolic volume (ESV)
How do we measure stroke volume?
Difference between EDV and ESV
What is the main thing which influences stroke volume?
Size of a person
How do you measure ejection fraction?
Stroke volume divided by EDV
What is the ejection fraction?
The amount of blood pumped out with each contraction
What happens in the rapid ejection phase?
Blood is pumped rapidly out of the left ventricle due to increased pressure
What happens in the slower ejection phase?
Blood is pumped out at a slower rate
What is the rapid filling phase?
Blood rapidly fills into the left ventricle
What is the slower filling phase?
Blood flows into the left ventricle at a slower pace
Heyyy bestie
Watch part 4.1 of CVS physiology and copy out the graph and label all these new terms as we need to know them!
Why do heart sounds get generated?
Sounds occur due to turbulence in blood flow
Describe the causes of the four heart sounds.
1st = closure of the AV (mitral and tricuspid) valves
2nd = closure of the semi-lunar (aortic and pulmonary) valves
3rd = rapid passive filling phase
4th = active filling phase
Which two heart sounds will you always hear?
1st (closure of mitral and tricuspid valves)
2nd (closure of aortic and pulmonary valves)
What are murmurs?
Any additional heart sounds other than the four discussed.
Are all murmurs bad?
No- innocent murmurs are common in infants and children
Pregnant women can also get physiological innocent murmurs
What happens between the first and second heart sound?
Systole
What happens after the second heart sound?
Diastole
What may cause a pathological heart murmur?
- Valve that should be open is narrowed or stenosed, causing turbulent blood flow
OR
- Valve which should be closed is leaky and allows blood to regurgitate back through it.
What can a systolic murmur sound like?
Lub shhh dub
Lub shhh dub
(considering normal heart sounds are often referred to as going lub dub, lub dub etc.)
What causes a systolic heart murmur?
Stenosis of aortic/pulmonary valves or
Regurgitation through mitral/tricuspid valves
What can a diastolic heart murmur sound like?
Lub dub shhhh
Lu dub shhhh
What can cause a diastolic heart murmur?
Stenosis of mitral/tricuspid valves or
Regurgitation through aortic/pulmonary valves
Why may a continuous heart tumour be heard?
Patent ductus arteriosus
What is the ductus arteriosus?
Small vessel that joins the aorta to the pulmonary trunk during development.
What happens to the ductus arteriosus after birth?
It shuts
What happens if the ductus arteriosus doesn’t close?
Leads to patent ductus arteriosus and, as a result, a continuous heart murmur.
