Cardiac cycle 1

Question 1

What occurs during P wave?

Answer 1

Depolarisation of SAN
Ventricles relax
Mitral valve open

Question 2

What occurs after P wave?

Answer 2

Atrial contraction
LA empties into LV- pressure of LA lowers
LV fills up with blood but dilates- pressure lower than LA
Prevents blood from going back into LA

Question 3

How long does QRS complex last?

Answer 3

80-120 ms

Question 4

What occurs during QRS complex?

Answer 4

1) Blood fills LV
2) Mitral valve closes as LV gets full, aortic valve closed
3) Isovolumic contraction begins- same volume but pressure increases
4) Volume squeezed- creates pressure of 120mmHG
5) Contraction allows aortic valve to open
6) Pressure is lower aorta than LV pressure so blood empty into
aorta at high speed
7) When blood ejected into aorta end isovolumic contraction
- Volume not same
- Isovolumic contraction then ejection

Question 5

What point does mitral valve close?

Answer 5

QRS complex

Question 6

What contraction occurs Left Ventricle during QRS complex?
What pressure?

Answer 6

120mmHG
Isovolumetric contraction- same vol, diff pressure

Question 7

What point does aortic valve open?

Answer 7

QRS complex

Question 8

What occurs during T wave?

Answer 8

Repolarisation of ventricle
Ventricles contracting- ejection decreases- fall pressure
ATP hydrolysis breaks bond Ca2+ and TnC
Muscles relax
Pressure drops 80mmHG
Aortic valve closes
25% volume left in LV
Isovolumic relaxation- until pressure 0mmHg

Question 9

What does pressure drop to during T wave?

Answer 9

80mmGH

Question 10

What does the P wave represent?

Answer 10

Atrial depolarisation

Question 11

What does QRS complex represent?

Answer 11

Ventricle depolarisation

Question 12

What does the T wave represent?

Answer 12

Ventricle repolarisation

Question 13

What does the PR interval represent?

Answer 13

Start atrial contraction
Ends beginning ventricle depolarisation

Question 14

What does ST segment represent?

Answer 14

Ventricles relaxing (repolarising)

Question 15

When does ventricular systole occur?

Answer 15

QRS complex

Question 16

What represents atrial depolarisation?

Answer 16

P wave

Question 17

What represents depolarisation of R and L ventricles?

Answer 17

QRS

Question 18

What does the P wave represent?

Answer 18

Depolarisation of atria

Question 19

What is PQ segment?

Answer 19

Signal slows when arrives at AV node

Question 20

Why is the signal slowed in the PQ segment? duration?

Answer 20

Allow blood from atria to fill ventricles
120-200ms

Question 21

What does QRS comlex represent?

Answer 21

Ventricular depolarisation
Pumping action ventricles
Ventricular systole

Question 22

What does ST segment represent?

Answer 22

Time for ventricle pump blood

Question 23

What does the T wave represent?

Answer 23

Final Ventricular relaxation/ diastole
Follows repolarization of the ventricles

Question 24

What occurs during diastole?

Answer 24

LA fills blood
Pressure increases- 12mmGH
Mitral valve opens
Continue filling 85-95% blood
Atrial pressure decreases- vent increases
Period equal pressure- diastasis

P wave arrives leads depolarisation SAN and LA
Fill rest ventricle

Question 25

What is term for equal pressure during filling of L ventricle from atria?

Answer 25

Diastesis

Question 26

Draw and label ECG wave?

Answer 26

Question 27

Define dystole?

Answer 27

Phase heart muscle relaxes Fills with blood

Question 28

Define systole?

Answer 28

Atria contract Ventricular systole contracts Atrial systole move blood from atria to ventricles Ventricular systole moves blood out heart to pulmonary and systemic circulations

Question 29

Answer 29

Question 30

What gives first heart sound?

Answer 30

Mitral valve closing during ventricular contraction

Question 31

What gives second heart sound?

Answer 31

Aortic valve opens Aortic pressure is greater than LV pressure

Question 32

Define diastasis?

Answer 32

LV pressure=L arterial pressire

Question 33

When does systole occur?

Answer 33

Between 1st and 2nd HS M1-A2

Question 34

Define preload?

Answer 34

Load before ventricular contraction measure of the degree of the ventricular stretch when the heart is at the end of diastole

Question 35

Define afterload?

Answer 35

Afterload is the force or load against which the heart has to contract to eject the blood

Question 36

Define afterload?

Answer 36

Load after ventricles starts contract

Question 37

Define Starlings law?

Answer 37

Larger volume of heart- greater energy of contraction Positive ionotropic effect

Question 38

Define Force-length interaction?

Answer 38

Decrease length sarcomere results lower force produced Cardiac sarcomere 80% length- 10% maximal force

Question 39

Define contractility?

Answer 39

Ability increase contraction velocity to achieve higher pressure independent of load

Question 40

Define elasticity?

Answer 40

Ability recover normal shape after sydtolic

Question 41

Explain compliance? Equation?

Answer 41

Relationship between change in stress and resultant strain (dP/dV)

Question 42

Define diastolic distensibility?

Answer 42

Pressure required fill ventricle to same diastolic volume

Question 43

Explain pressure volume loops?

Answer 43

Contractility end systolic pressure-volume relationship Compliance reflected end diastolic pressure-volume relationshi0

Answer 44

Question 45

What does PR segment represent?

Answer 45

Delay AVN

Question 46

Draw and mark main stages?

Answer 46