Cardiac Cycle

Question 1

What is ventricular systole?

Answer 1

Contraction of the ventricles

Question 2

What three things are SV into the aorta determined by (strength and velocity)?

Answer 2

1. myocardial contractility (EC coupling)
2. preload (sarcomere length)
3. afterload (magnitude)

Question 3

What does the peak of the R-wave indicate?

Answer 3

onset of ventricular contraction and initial vibration of first heart sound
ventricular systole
*indicates the electrical event

Question 4

When is the earliest rise in ventricular pressure during ventricular systole?

Answer 4

after atrial contraction

Question 5

What is isovolumic contraction?

Answer 5

phase between the start of ventricular systole and the opening of the semilunar valves
- because ventricle volume is constant

Question 6

How does the LV increase area to decrease pressure?

Answer 6

LV contracts during twist base is being pulled down -> stretching out ventricle = increased area to decrease the pressure

Question 7

What indicates the onset of ejection?

Answer 7

opening of semilunar valves

Question 8

What are the two phases of ejection?

Answer 8

rapid ejection - earlier and shorter
reduced ejection - later and longer

Question 9

What 3 ways is rapid ejection different from reduced ejection?

Answer 9

1. sharp rise in ventricular and aortic pressure that terminates at peak pressures
2. abrupt decrease in ventricular volume
3. greater aortic blood flow

Question 10

What does the sharp decrease in the LA pressure curve at the onset of ejection result from?

Answer 10

the descent of the base of the heart to stretch the atria

Question 11

Why does aortic pressure decline during reduced ejection?

Answer 11

blood flow from the aorta to the periphery exceeds ventricular output

Question 12

What does blood returning to the atria produce throughout ventricular systole?

Answer 12

a progressive increase in atrial pressure

Question 13

What is the relationship between LV and aortic pressure during the first third of the ejection period?

Answer 13

LV pressure slightly exceeds aortic pressure, and flow accelerates

Question 14

What is the relationship between LV and aortic pressure during the last two-thirds of the ejection period?

Answer 14

aortic pressure slightly exceeds aortic pressure, and flow decelerates

Question 15

What is the reversal of the AV pressure gradient during ejection a result of?

Answer 15

the potential energy in the stretch arterial walls, which produces a deceleration of blood flow into the aorta

Question 16

What does the peak of the flow curve coincide with?

Answer 16

the point LV pressure curve intersects with the aortic pressure curve during ejection
- therefore, flow decelerates because the pressure gradient has been reversed

Question 17

During RV ejection what is caused?

Answer 17

shortening of the free wall of the RV (descend of the tricuspid ring) = lateral compression of the chamber

Question 18

During RV ejection what is the main cause of ejection?

Answer 18

there is very little shortening of the base to apex axis, ejection is accomplished by compression of the LV chamber
*decreasing circumference

Question 19

In venous pulse, what is the a wave caused by?

Answer 19

atrial contraction

Question 20

In venous pulse, what is the c wave caused by?

Answer 20

the impact of the adjacent common carotid artery and, to some extent, by the transmission of a pressure wave produced by the abrupt closure of the tricuspid valve in early ventricular systole

Question 21

In venous pulse, what is the v wave caused by?

Answer 21

the pressure of blood from peripheral vessels and abrupt opening of the tricuspid valve

Question 22

What does the P-wave indicate?

Answer 22

atrial repolarization

Question 23

What does the T-wave indicate?

Answer 23

ventricular repolarization

Question 24

What does the QRS complex indicate?

Answer 24

ventricular depolarization

Question 25

What does the aortic valve closure produce?

Answer 25

the incisura on the descending limb of the aortic pressure curve and the second heart sound

Question 26

What does the aortic valve closure mark?

Answer 26

the end of ventricular systole

Question 27

What is isovolumic relaxation?

Answer 27

the phase between the closure of the semilunar valves and the opening of the AV valves ventricular diastole

Question 28

What is isovolumic relaxation characterized by?

Answer 28

a precipitous fall in ventricular pressure without a change in ventricular volume

Question 29

When does rapid refilling occur?

Answer 29

immediately upon opening of AV vales

Question 30

What indicates the onset of the rapid filling phase?

Answer 30

decrease in LV pressure (pressure gradient) below LA pressure -> opening of mitral valve

Question 31

What does a rapid flow of blood from atria to relaxing ventricles produce?

Answer 31

a decrease in atrial and ventricular pressures and a sharp increase in ventricular volume

Question 32

What is diastasis?

Answer 32

follows rapid filling, a phase of slow filling blood returning from the periphery flows into RV, and blood from the lungs into LV *a phase in diastole, not diastole itself

Question 33

What is diastasis indicated by?

Answer 33

a small, slow addition to ventricular filling indicated by a gradual rise in atrial, ventricular, and venous pressures, as well as an increase in ventricular volume

Question 34

How can diastasis function be measured?

Answer 34

by measuring the velocity of blood across the mitral valve (ultrasound)

Question 35

What is the E/A ratio?

Answer 35

early to late filling want a high ratio -> minimal reliance on the atrium to push blood more blood during rapid filling (sucking blood) -> pressure gradient

Question 36

What is the onset of atrial systole?

Answer 36

occurs soon after the beginning of the P-wave and transfer of blood from the atrium to the ventricle (ventricular filling)

Question 37

What is atrial systole responsible for?

Answer 37

small increase in atrial, ventricular, and venous pressure, as well as ventricular volume

Question 38

Why does the atrial pressure barely exceed ventricular pressure throughout diastole?

Answer 38

indicates a low resistance pathway across open AV valves function as a singe chamber

Question 39

Why can atrial contraction force blood in both directions?

Answer 39

because there are no valves at the junction of venae cavae and RA or at pulmonary veins and LA - little blood is pumped back into venous tributaries during brief atrial contraction because of the inertia of inflowing blood

Question 40

What two conditions show that atrial contraction is not essential for ventricular filling?

Answer 40

atrial fibrillation - multiple ectopic foci (unsynchronized contraction) complete heart block - SA and Av nodes don't function in synchrony

Question 41

What is the contribution of atrial contraction governed by?

Answer 41

HR and structure of AV valves

Question 42

How does slow HR affect atrial contraction contribution?

Answer 42

filling ceases toward the end of diastasis, atrial contraction contributed little to filling

Question 43

How does tachycardia affect atrial contraction contribution?

Answer 43

diastasis is shortened, the atrial contribution can become substantial, especially immediately after rapid filling when AV pressure gradient is maximal (~10-20% EDV during exercise)

Question 44

What happens if HR becomes so great diastasis begins to encroach on rapid filling?

Answer 44

atrial contraction becomes very important to propel blood forward to fill the ventricle

Question 45

What can happen if the filling period is too brief?

Answer 45

cannot prevent inadequate filling -> syncope (fainting) - Bp -> CO -> impaired squeeze of filling

Question 46

What happens if atrial contraction becomes simultaneous with ventricular contraction?

Answer 46

no atrial contribution to ventricular filling - won't generate more pressure with atria than with ventricle