Cardiac Cycle

Question 1

Cardiac cycle

Answer 1

single beat of the heart; systole + diastole

Question 2

Systole

Answer 2

ventricles contract

Question 3

Diastole

Answer 3

relaxation/ventricles fill

Question 4

Isovolumetric contraction

Answer 4

happens right after QR; the time when the ventricle volume is constant but increasing pressure. Start of isovolumetric contraction is the start of systole at peak R.

Question 5

Ventricular contraction leads to what?

Answer 5

Increased ventricular pressure

Question 6

S1 sound

Answer 6

sounds of vibrations from mitral valve closing;
closes when L ventricle pressure exceeds L atrial pressure;
happens right before isovolumetric contraction

Question 7

Peak R significance

Answer 7

• start of systole and isovolumetric contraction

- end of diastole

Question 8

Diastolic dysfunction

Answer 8

end-diastole pressure greater than 16 mmHg; normal average is 8 mmHg

Question 9

When does the aortic valve open?

Answer 9

When L ventricular pressure exceeds aortic pressure;

rapid ejection of blood to aorta

Question 10

Results of rapid ejections of blood into aorta?

Answer 10

• increased aortic pressure

- wall of aorta stretches

Question 11

Stroke volume

Answer 11

amount of blood that flows out of the L ventricle/minute
about 70 mls
can be measured by Doppler ultrasound, radionuclide counts and echocardiography

Question 12

Stroke volume equation

Answer 12

SV= ventricular end-diastole volume- ventricular end-systole volume

Question 13

Ejection fraction

Answer 13

stroke volume/end-diastole volume

Question 14

Cardiac output

Answer 14

blood ejected from aorta per MINUTE;

usually about 5 liters

Question 15

Reduced ejection phase

Answer 15

Repolarization of the ventricles, results in T wave on EKG. Aortic pressure will then exceed L ventricular pressure.

Question 16

Why doesn’t the aortic valve immediately close when aortic pressure starts to exceed L ventricular pressure?

Answer 16

The blood flow has a large amount of inertia which translates to kinetic energy. Valve doesn’t close immediately.

Question 17

Aortic elastic recoil

Answer 17

pushes blood into rest of circulatory system

Question 18

End systolic volume

Answer 18

volume left in ventricle after systole

Question 19

End diastolic volume

Answer 19

volume left in ventricle after atrial contraction or diastole
about 120 mL

Question 20

Left ventricular end-diastolic pressure

Answer 20

Pressure in the ventricle at the end of diastole, or being filled. Usually 12 mmHg

Question 21

Major difference between right and left heart

Answer 21

peak systolic pressure
in the right heart it is 24mmHg
in the left heart it is 130mmHg

Question 22

Pressure/volume loop of the L ventricle in a single cardiac cycle

Answer 22

mitral valve opens–> LV fills; LV P drops–> volume increases in LV and slight increase in LV P–> mitral valve closes–> isometric contraction occurs–> increase in LV pressure to 80 mmHg–> aortic valve opens when LV P exceeds aortic P–> LV muscles shorten and eject blood–> LV P increases even more as blood is pushed out in rapid ejection phase–> LV muscle relaxes/reduced ejection due to ventricular repolarization–> end systolic volume/P; closure of aortic valve–> isovolumetric relaxation begins

Question 23

What happens to the R atrium right after P wave?

Answer 23

contraction of R atrium

Question 24

What happens to the R atrium pressure right after QRS?

Answer 24

tricuspid valve bulges into R atrium as RV P increases due to isovolumetric contration/systole

Question 25

What happens to the R atrium right after the repolarization of the ventricles (T wave)?

Answer 25

R atrium fills; tricuspid valve closed

Question 26

Cardiac Output Equation

Answer 26

CO= stroke volume x heart rate

Question 27

Fick’s Equation

Answer 27

Rate of O2 absorption in the circulation= change in O2 in pulmonary blood x pulmonary blood flow

Pulmonary blood flow= RV output= LV output–> O2 uptake measurements determine cardiac output.

Question 28

QCv

Answer 28

O2 in venous blood entering the lungs/min

Question 29

QCa

Answer 29

O2 in arterialized blood leaving lungs/min

Question 30

O2 capillary bed uptake/min

Answer 30

QCa-QCv

Question 31

In steady state, O2 uptake by blood is equal to?

Answer 31

the O2 removed by alveolar gas in lungs (VO2)

–> O2 capillary uptake= VO2

Question 32

VO2=

Answer 32

QCa-QCv

–> Q (cardiac output)= VO2/Ca-Cv