L11 - Cardiac Cycle

Question 1

Define the cardiac cycle

Answer 1

The series of mechanical and electrical events which occur and repeat with each beat of the heart

Question 2

4 phases (brief) of the cardiac cycle

Answer 2

Innflow of blood
Isovolumetric contraction
Outflow of blood
Isovolumetric relaxation

Question 3

What does isovolumetric mean

Answer 3

Contraction or relaxation of the chambers with both of the valves shut, lead to no change in volume but a change in pressure is seen

Question 4

What ECG wave represents atrial depolarisation

Answer 4

P wave

Question 5

Since the SA node is found in the right atrium, does the right ventricle contract before the left atrium, why?

Answer 5

No both conduct simulataneously thanks to the fast conduction velocity of the impulse via Bachmans bundle

Question 6

What occurs when the atria contract

Answer 6

Pressure in the atria increases and blood is squeezed into the ventricles

Question 7

How much of the blood entering the ventricles is passive, how much is down to the contraction of the atria

Answer 7

80% passive, around 10% from atrial contraction

Question 8

What is the contraction of the atria also known as

Answer 8

The atrial kick

Question 9

What occurs once the atria have finished contraction

Answer 9

Atrial pressure falls and a pressure gradient reversal occurs across the AV valves causing the valves to float upward before closure

Question 10

What occurs to the AV valves after the atria have finished contraction

Answer 10

Pressure gradient reversal across the AV valves causes them to float upwards before they close

Question 11

At phase 1 what is maximum

Answer 11

The volumes of the ventricles

Question 12

When do end diastolic volume (what phase)

Answer 12

1

Question 13

What is end disastolic volume

Answer 13

The maximum volume of blood in the ventricles

Question 14

What is LVEDV

Answer 14

Left ventricle end diastolic volume

Question 15

What is the typical LVEDV and what does this represent

Answer 15

120ml

The ventricular preload

Question 16

What is the ventricular preload

Answer 16

The intial strectching of the cardiomyocytes prior to contraction

Question 17

Typical end diastolic pressure of the Lv

Answer 17

8-12 mmHg

Question 18

Typical end diastolic pressure of the RV

Answer 18

3-6 mmHG

Question 19

Why is the end diastolic pressure of the RV lower than the LV

Answer 19

Wall of the epithelium is thin in pulmonary circulation, gaps between the capillary endothelial cells to allow movement of substances.
If pressure was too high fluid would be forced through the gaps and into the lungs - would cause oedema

Question 20

What does the QRS complex represent - what phase is this this the beginning of

Answer 20

Ventricular depolarisation, marks the start of phase 2

Question 21

What is the state of all of the valves in phase 2

Answer 21

All of the valves are closed

Question 22

What does ventricular depolarisation trigger

Answer 22

Excitation, contraction coupling

Question 23

What can be said about dP/dt during phase 2

Answer 23

Maximal early in phase 2

Question 24

When do the AV valves close

Answer 24

When the intraventricular pressure exceeds the atrial pressure

Question 25

What also contracts during ventricular contraction, what does this do and prevent

Answer 25

Contraction of the paillary muscles, causing tension in the cordae tendinea attached to the valve leaflets. The tension in the AV valve leaflets prevent them from bulging backward and inverting

Question 26

What causes the first heart sound

Answer 26

The closing of the AV valves

Question 27

Why does the first heart sound compose of two parts? What is the gap between the two sounds

Answer 27

Because mitral valve closes slightly earlier than the triscuspid valve

Question 28

Which side of the heart is the tricuspid

Answer 28

tRiscuspid RIGHT

Question 29

Which side of the heart is the mitral valve

Answer 29

mitraL LEFT

Question 30

Phase 3 is also known as

Answer 30

Isovolumetric contraction

Question 31

What two valve movements does phase 3 occur between

Answer 31

The closure of the AV valves and then the openig of the pumonary/aortic valves

Question 32

Because their is no change in volume, when contractign what happens

Answer 32

Rapid rise in pressure

Question 33

During isovolumetric contraction what determines the dP/dt

Answer 33

Rate of contraction of the muscle fibres which is in turn governed by mechanisms governing excitation contraction coupling

Question 34

What causes the c wave in LAP, when does this occur

Answer 34

Bulging back of mitral valve leaflets into the left atrium ==> causes the volume here to decrease slightly

Question 35

What is the state of the two valves during phase 4

Answer 35

Aortic and pulmonary valves open | The AV valves remain closed

Question 36

At what point does ejection begin

Answer 36

When the intraventricular pressure exceeds the pressure in the aortic and pulmonary arteries which then causes the respective valves to open

Question 37

When is MAX outflow velocity reached

Answer 37

Early in the ejection phase

Question 38

Are any heart sounds made during ejection

Answer 38

No opening of the healthy valves is a normally silent process

Question 39

What occurs to LAP during ejection (phase 4)

Answer 39

Initially decreases as the atrial base is pulled downward expanding the atrial chamber

Question 40

What occurs during phase 5

Answer 40

Isovolumetric relaxation

Question 41

What phase does isovolumetric relaxation occur in

Answer 41

5

Question 42

When do the aortic and pulmonary valves close

Answer 42

When the intraventricular pressure has fallen sufficiently

Question 43

Does the aortic or pulmonary valve close first

Answer 43

Aortic closes first

Question 44

What causes the second heart sound

Answer 44

The closing of the aortic and pulmonary valves

Question 45

What is the closure of the aortic and pulmonary valve associated with

Answer 45

A small backflow of blood into the ventricles and a characterisic notch (dicrotic notch)

Question 46

What is the rate of pressure decline in the ventricles determined by, what is this known as

Answer 46

Determined by the rate of relaxation of the ventriuclar muscle, known as leuistropy (rate of relaxation)

Question 47

What is leuisitropy regualted by

Answer 47

Regulated by the sarcoplasmic reticulum which is responsible for re-sequestering Ca ions following contraction

Question 48

When all of the valves have closed at the muscle is relaxing what does this cause

Answer 48

Decrease in pressure but no change in volume | Isovolumetric releaxation

Question 49

Once the aortic valve has shut what is the volume of blood left known as, what is a typical value for this

Answer 49

Left ventricular end systolic volume | 50ml

Question 50

What is the equation for stroke volume, show how a typical stroke volume is 50 mls

Answer 50

LVEDV - LVESV = SV | 120 - 50 = 70 mls

Question 51

During isolvolumetric relaxation of the ventricles what is happening to LAP

Answer 51

Continuing to rise due to venous return of the blood

Question 52

Phase 6 is known as

Answer 52

Rapid filling

Question 53

Which phase is rapid filling

Answer 53

6

Question 54

When/how does ventricular filling begin

Answer 54

As ventricles relax intraventricular pressure falls below the pressure in the atria this causes the AV valves to open and blood to flow into the ventricles

Question 55

Why does intraventricular pressure continue to fall despite them filling

Answer 55

They are still relaxing

Question 56

What occurs to LAP when the mitral valve opens

Answer 56

Rapid fall

Question 57

When is the peak of the LAP, what is this called, what occurs after

Answer 57

Peak just before the mitral valves open known as the v wave, followed by the y-descent of the LAP

Question 58

Where is a similar V and Y wave and descent seen in the body

Answer 58

Found in the right atrium and the jugular vein

Question 59

What can be said about S3

Answer 59

Usually silent

Question 60

What would some reasons for a sound being heard at S3 be

Answer 60

Tensing of the chordae tendinae or AV ring | Could be the turbulent flow of blood back into the ventricles

Question 61

What occurs as the ventricles continue to fill

Answer 61

They become less compliant and the intraventricular pressure rises, this reduced the pressure gradient across the AV valves so rate of filling is reduced

Question 62

What % of ventricular filling is passive

Answer 62

90%

Question 63

A wave in LAP represents

Answer 63

Atrial systole

Question 64

What is S1

Answer 64

Closure of the mitral and tricuspid valve, marks the end of diastole and beginning of ventricular systole

Question 65

What is S2

Answer 65

Closure of the aortic and pulmonary valves at the end of systole

Question 66

What is S3

Answer 66

Low pitched rapid entry of blood from the atria to te ventricles

Question 67

What part of the stephoscope is S3 best heard through

Answer 67

The bell