The Cardiac Cycle

Question 1

what is the cardiac cycle?

Answer 1

all of the events that occur from the beginning of one heart beat to the beginning of the next

Question 2

what is diastole?

Answer 2

when the ventricles relax and fill with blood

Question 3

what is systole?

Answer 3

when the ventricles contract and pump blood into the aorta and pulmonary artery

Question 4

how long are systole and diastole in a heart with a heart rate of 75bpm?

Answer 4

systole = 0.3s
diastole = 0.5s

Question 5

what are the five events that occur during the cardiac cycle?

Answer 5

passive filling 
atrial contraction 
isovolumetric contraction 
ventricular ejection 
isovolumetric ventricular relaxation

Question 6

describe the pressure in the heart during passive filling

Answer 6

close to zero

Question 7

what valves are open during passive filling and what does this allow?

Answer 7

AV valves

ventricles fill

Question 8

which valves are closed during passive filling?

Answer 8

aortic and pulmonary

Question 9

how full do the ventricles become during passive filling?

Answer 9

around 80%

Question 10

what does the P wave on an ECG represent?

Answer 10

atrial depolarisation

Question 11

where on an ECG does atrial contraction occur?

Answer 11

between the P wave and the QRS complex

Question 12

what completes the end diastolic volume?

Answer 12

atrial contraction

Question 13

when does ventricular contraction start on an ECG?

Answer 13

after the QRS

Question 14

what does the QRS on an ECG signal?

Answer 14

ventricular depolarisation

Question 15

when do the AV valves shut?

Answer 15

when the ventricular pressure exceeds atrial pressure in isovolumetric ventricular contraction

Question 16

what produces the first heart sound?

Answer 16

closure of the AV valves

Question 17

what are the two AV valves?

Answer 17

mitral

tricuspid

Question 18

what makes isovolumetric ventricular contraction isovolumetric?

Answer 18

all valves are closed so volume doesn’t increase, but pressure does

Question 19

when does ventricular ejection occur?

Answer 19

when ventricular pressure exceeds the pressure of the aorta and pulmonary artery

Question 20

what valves open in ventricular ejection?

Answer 20

aortic and pulmonary

Question 21

what is left in the heart after ventricular ejection?

Answer 21

the end systolic volume

Question 22

what does the T wave in ECG represent?

Answer 22

ventricular repolarisation

Question 23

what causes the second heart sound and when does this occur?

Answer 23

when the aortic and pulmonary valves close

when ventricular pressure falls below aortic/pulmonary pressure

Question 24

what signals the start of isovolumetric ventricular relaxation?

Answer 24

closure of the aortic and pulmonary valves

Question 25

what signals the start of a new cardiac cycle?

Answer 25

the AV valves opening