Week 18: The Cardiac Cycle

Question 1

What is the cardiac cycle?

Answer 1

the sequence of pressure and volume changes that takes place during cardiac activity

Question 2

What brings about the mechanical events in the cardiac cycle?

Answer 2

by rhythmic changes in cardiac electrical activity

Question 3

how to calculate max heart rate?

Answer 3

220 bpm- age in years

Question 4

When does a valve open?

Answer 4

pressure is greater behind the valve than in front

Question 5

when does a valve close?

Answer 5

when pressure is greater in fronton way valve=closes

Question 6

What is the ECG a record of?

Answer 6

overall spread of electrical activity through the heart.

Electrical activity is the precursor for mechanical activity

Question 7

When is the AV valve open?

Answer 7

When the Atria are depolarising between P and S on ECG

Question 8

When is the left ventricle at its peak blood volume?

Answer 8

Between, S and shortly after.
After depolarisation (R)

Question 9

When is the left ventricle at its lowest blood volume?

Answer 9

Midpoint of T (repolarisation) and when the corn ends

Question 10

When does mid-diastole occur?

Answer 10

between T and P sections.

after ventricular depolarisation and before atrial depolarisation

Question 11

When does the atria fill up with blood?

Answer 11

between T and P.

Mid-diastole

Question 12

When do the ventricles fill passively? (passive filling)

Answer 12

during mid-diastole when AV vales are open. accounts for 80% of final diastolic volume

Question 13

Why are the aortic and pulmonary valves closed during mid-diastole?

Answer 13

higher pressure in the arteries compared to ventricular pressure

Question 14

What happens to the ECG curve during late diastole?

Answer 14

P wave of ECG occurs

Question 15

When do the atria contract?

Answer 15

towards end of P wave- increase atrial pressure

Question 16

What happens when the atria contract?

Answer 16

most of the blood in the atria is propelled into ventricles, adds 20% to ventricular filling

Question 17

What happens to ventricular pressure when atria force blood into them?

Answer 17

increase pressure slightly

Question 18

What are some basic steps in late diastole?

Answer 18

1) SA node reached threshold, AP generated.
2) AP conducted across arterial tissue of heart via internodal pathway
3) Causing atrial muscle to collectively depolarise, rise to P wave
4) Increase atrial pressure, squeeze bait more blood into ventricles

Question 19

When does diastole end on ECG?

Answer 19

onset of ventricular contraction/depolarisation

Question 20

What happens during end of diastole/early systole?

Answer 20

ventricles contract at the endow QRS complex.

Question 21

What happens to ventricular pressure during early systole?

Answer 21

rapid increase in pressure

Question 22

What happens to valves during early systole?

Answer 22

AV valves snap shut- first heart sound

AV and aortic valves are shut … nothing in and nothing leaves

Question 23

What is the phase called when both aortic and AV valves are closed?

Answer 23

isovulumetric or isometric phase

Question 24

What happens to the valves ejection period?

Answer 24

ventricular pressure exceeds arterial pressure, aortic and pulmonary valve pulmonary valves open.

Question 25

What is the pressure difference in the pulmonary artery for ejection period?

Answer 25

8mmHg to 25 mmHg during systole

Question 26

What makes the second heart sound?

Answer 26

closing of the aortic valve during end of ventricular systole

Question 27

What makes the first heart sound?

Answer 27

closing AV valves of the during early systole

Question 28

What is the end of ventricular systole on ECG?

Answer 28

down slope of T wave

Question 29

What happens during end of ventricular systole?

Answer 29

ventricles relax, ventricular pressure falls below aortic pressure.
aortic valves shut

Question 30

What does the second heart sound cause?

Answer 30

blip/notch on the aortic pressure curve.

called a dicrotic notch

Question 31

What happens to the valves in the end pf ventricular systole?

Answer 31

AV valve also shut, no blood in or out.

isomeric ventricular relaxation

Question 32

What happens during filling period?

Answer 32

ventricular pressure falls below atrial pressure
AV valve opens
Blood which entered during ventricular systole is released into the ventricles by opening of AV valve

Question 33

What are the changes in pressure and volume during filling period?

Answer 33

Atrial and ventricular pressures fall sharply and ventricular volume increases rapidly

Question 34

What are the 5 phases in the cardiac cycle?

Answer 34

1) filling period
2) atrial contraction
3) isovolumetric ventricular contraction
4) ejection
5) isovolumetric ventricular relaxation

Question 35

What is used to detect the heart sounds?

Answer 35

phonocardiogram

Question 36

What are abnormal sounds in pathological conditions called?

Answer 36

murmurs