L11 - Cardiac Cycle Flashcards Preview

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Flashcards in L11 - Cardiac Cycle Deck (67)
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1

Define the cardiac cycle

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

2

4 phases (brief) of the cardiac cycle

Innflow of blood
Isovolumetric contraction
Outflow of blood
Isovolumetric relaxation

3

What does isovolumetric mean

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

4

What ECG wave represents atrial depolarisation

P wave

5

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

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

6

What occurs when the atria contract

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

7

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

80% passive, around 10% from atrial contraction

8

What is the contraction of the atria also known as

The atrial kick

9

What occurs once the atria have finished contraction

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

10

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

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

11

At phase 1 what is maximum

The volumes of the ventricles

12

When do end diastolic volume (what phase)

1

13

What is end disastolic volume

The maximum volume of blood in the ventricles

14

What is LVEDV

Left ventricle end diastolic volume

15

What is the typical LVEDV and what does this represent

120ml
The ventricular preload

16

What is the ventricular preload

The intial strectching of the cardiomyocytes prior to contraction

17

Typical end diastolic pressure of the Lv

8-12 mmHg

18

Typical end diastolic pressure of the RV

3-6 mmHG

19

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

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

20

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

Ventricular depolarisation, marks the start of phase 2

21

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

All of the valves are closed

22

What does ventricular depolarisation trigger

Excitation, contraction coupling

23

What can be said about dP/dt during phase 2

Maximal early in phase 2

24

When do the AV valves close

When the intraventricular pressure exceeds the atrial pressure

25

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

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

26

What causes the first heart sound

The closing of the AV valves

27

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

Because mitral valve closes slightly earlier than the triscuspid valve

28

Which side of the heart is the tricuspid

tRiscuspid RIGHT

29

Which side of the heart is the mitral valve

mitraL LEFT

30

Phase 3 is also known as

Isovolumetric contraction