The cardiac cycle

Question 1

What is the isovolumic ventricular contraction phase?

Answer 1

First phase of ventricular contraction pushes AV valves shut (mitral/tricuspid) but does not crate enough pressure to open the semilunar valves.

Question 2

Run through the 5 stages of heart contraction and what happens at which stage

Answer 2

Late diastole - both sets of chambers are relaxed and the ventricles fill passively
Atrial Systole - Atrial contraction forces a small amount of additional blood into ventricles
Isovolumic ventricular contraction -first phase of contraction that pushes AV valves shut but doesn’t create enough pressure to open the semi lunar valves
Ventricular ejection- ventricular pressure exceeds pressure in the arteries, this opens the semil lunar valve and blood is ejected
Isovolumic ventricular relaxation - as ventricles relax the pressure decreases and blood flows back into the cupsps of the semilunar valves that closes them off.

Question 3

What is systolic pressure?

Answer 3

Maximum pressure reached in the aorta (arteries) leaving the heart.

Question 4

What is diastolic pressure?

Answer 4

The pressure the aorta DIES DOWN to between heart beats

Question 5

What is Mean Arterial Pressure and how can we work this out roughly?

Answer 5

It is the average pressure, which can be worked out by adding 1/3 the pulse pressure to the diastolic pressure.

Question 6

What is the pulse pressure?

Answer 6

Systolic pressure - diastolic pressure, basically how much the pressure varies over the pulse between diastolic and systolic pressure.

Question 7

What is EDV?

Answer 7

End diastolic volume - how much blood is left in the heart following the diastolic phase, should be the bigger number of EDV and ESV because the ventricle has finished the filling up stage. Can be around 140.

Question 8

What is ESV?

Answer 8

End systolic volume, the amount of blood left in the heart following systole, so will be less than edv as the heart has just ejected all the blood that was contained within it. For refrence eg. 60ml

Question 9

What is the stroke volume?

Answer 9

The amount of blood ejected from the heart per beat. can be calculated by edv-esv

Question 10

What is ejection fraction?

Answer 10

It is the amount of blood ejected from the heart in relation to the total volume that was in the heart before contraction (sv/edv)

Question 11

What is the A-wave and what causes it?

Answer 11

A fro Atrial contraction! The pressure caused from the contration of the atria. Occurs just after the p wave on the ecg and before the closure of the mitral valve.

Question 12

What is the C wave and what causes it?

Answer 12

C for cuspid - caused by the bi/tri cuspid valve bowing into the atria increasing the atrial pressure. Again, related to the atria, but this time is built up during the isovolumic contraction phase of the ventricles as the av valve gets pushed slightly into the atrial space and thus decreasing the volume and increasing the pressure.

Question 13

What is the V wave and what is it caused by?

Answer 13

V for Volumic! As the mitral valve is shut, the atrial pressure continues to increase as it fills with blood from the vena cava and has nowhere to go, so willgradually increase the atrial pressure until the av valve opens (caused by the pressure in the ventricle dropping below that of the atium)

Question 14

When do the rapid and slow ejection/contraction phases occur?

Answer 14

rapid phases always begin first and are followed by the slow phases, due to the bigger changes in pressure initially.

Question 15

What is stenosis?

Answer 15

Narrowing of a valve, could be due to calcification or if it isn’t opening properly.

Question 16

What are heart sounds caused by?

Answer 16

Turbulent flow of blood.

Question 17

Lub Dub Lub Dub Lub Dub

What causes the lub and what causes the dub?

Answer 17

Lub (1st heart sound) - turbulent blood caused by the closure of the av valves (tri/bicuspid valves) on initial contraction of the ventricle

Dub is the second heart sound of turbulent blood caused by the aortic and pulmonary valves (semi-lunar) shutting.

The flow of blood out of the ventricles is smooth flowing and not turbulent so not loud.

Question 18

What are the 4 normal heart sounds and when would they be heart?

Answer 18

1st = closure of the AV valves (tri&bi cuspid)
2nd = closure of the pulmonary/aortic valves (semi lunar)
3rd = fainter, but is rushing of blood into the ventricle in the rapid filling phase
4th = fainter, the active filling phase (atrial contraction)

Question 19

What are abnormal heart sounds called? And what are reasons for them and how do they present?

Answer 19

murmurs

Can be due to either stenosis (causing a murmur whilst the valve is open due to the narrowing), or due to leaky valves, causing a murmur when the valve is shut.

Present as murmor during diastole - could be due to stenosis in the av valve or leaky (regurgitation through the) semi lunar valves. Murmur during systole would be stenosis of the semi lunar valves or leaky (regurgiutation through the) av (bi/tri cuspid valves)

Also could be a hole between the ventricles (septal defect), which would cause a murmur continually throughout the cardiac cycle.

Question 20

What is the phonocardiogram?

Answer 20

The genaration of heart sounds, comes from turbulent blood flow, most often caused by closure of valves.