Lecture 17 - The Cardiac Cycle

Question 1

What causes a valve to open

Answer 1

When the pressure behind it is greater than the pressure in front of it

Question 2

What do the valves prevent

Answer 2

Backflow of blood

Question 3

What are the 5 phases of the cardiac cycle

Answer 3

Phase one - passive filling
Phase two - atrial contraction
Phase three - isovolumetric ventricular contraction
Phase four - ejection
Phase five - isovolumetric ventricular relaxation

Question 4

What are the heart sounds generated by

Answer 4

The closing of the valves

Question 5

What is used to detect the heart sounds

Answer 5

A phonocardiogram

Question 6

What does the first heart sound coincide with

Answer 6

The beginning of systole

Question 7

What produces the first heart sound

Answer 7

Closure of the AV valve

Question 8

What does the second heart sound coincide with

Answer 8

The onset of diastole

Question 9

What is the second heart sound produced by

Answer 9

Closure of the aortic and pulmonary valves

Question 10

Abnormal heart sounds in pathological conditions are known as

Answer 10

Murmurs

Question 11

What happens to the pressure of the atria and ventricles during phase 1

Answer 11

The ventricular pressure falls below the atrial pressure

Question 12

What happens when the ventricular pressure falls below the atrial pressure

Answer 12

The AV valves open

Question 13

What happens during phase one

Answer 13

Blood which entered the atria during ventricular systole is released into the ventricles

Question 14

When blood starts to move into the ventricles what happens to the pressure within the heart chambers

Answer 14

The atria and ventricular pressure fall rapidly

Question 15

What % of the final filled volume do the ventricles contain at the end of phase one

Answer 15

80%

Question 16

Are the aortic and pulmonary valves open or closed during phase one

Answer 16

Closed

Question 17

Phase one is equivalent to what on the ECG

Answer 17

TP interval

Question 18

During mid-diastole what blood is flowing into the atria

Answer 18

Blood from the venous system

Question 19

What occurs during phase two

Answer 19

The SA node produces an AP so the atrial muscle cells are stimulated to depolarise

Question 20

What is late diastole represented by on the ECG

Answer 20

The P wave

Question 21

What happens towards the end of the P wave

Answer 21

The atrial contract, increasing atrial pressure

Question 22

What happens when the atria contract

Answer 22

Most of the blood is propelled into the ventricle and ventricular pressure increases slightly

Question 23

Volume in each ventricle at the end of diastole is

Answer 23

Roughy 130ml for standing and 160ml for lying down

Question 24

Are the AV valves open or closed at the end of phase two

Answer 24

Open

Question 25

What marks the end of diastole

Answer 25

The beginning of ventricular contraction

Question 26

What happens to the AP after atrial contraction

Answer 26

It is conducted to the ventricular muscle

Question 27

What is formed on the ECG when ventricular muscle is stimulated

Answer 27

The QRS complex

Question 28

What happens to the ventricular pressure during phase 3

Answer 28

There is a rapid increase in ventricular pressure

Question 29

What does the rapid increase in ventricular pressure cause

Answer 29

The AV valves to snap shut

Question 30

Are the aortic and pulmonary valves open during phase 3

Answer 30

No

Question 31

Why is phase three known as the isovolumetric stage

Answer 31

As all the valves are shut so no blood can flow in or out of the ventricles

Question 32

When will the aortic valves open

Answer 32

Only when the pressure of the ventricles exceeds the pressure in the aorta

Question 33

What happens during phase four

Answer 33

The ventricular pressure exceeds the aortic pressure and the aortic and pulmonary valves open

Question 34

What is the diastolic pressure of the aorta

Answer 34

80mmHg

Question 35

What is the systolic pressure of the aorta

Answer 35

120mmHg

Question 36

What is the diastolic pressure of the pulmonary artery

Answer 36

8 mmHg

Question 37

What is the systolic pressure of the pulmonary artery

Answer 37

25 mmHg

Question 38

What is phase 5 represented by on the ECG

Answer 38

The T wave

Question 39

What does the T wave show

Answer 39

Ventricular repolarisation

Question 40

What occurs during phase 5

Answer 40

The end of ventricular systole. The ventricular muscle is starting to relax

Question 41

What occurs to ventricular pressure during phase 5

Answer 41

It starts to fall below atrial pressure

Question 42

What does the diacritic notch show

Answer 42

The ventricular pressure falling below atrial pressure

Question 43

What valves are shut during phase 5

Answer 43

AV, aortic and pulmonary valves