The Cardiac Cycle

Question 1

What is blood clotting?

Answer 1

A series of steps that take place which results in a blood clot

Question 2

Describe the process of blood clotting

Answer 2

1. The damaged cells release the enzyme thromboplastin
2. Thromboplastin converts the plasma protein prothrombin into the enzyme thrombin
3. Thrombin converts the soluble plasma protein fibrinogen into the insoluble protein fibrin
4. Fibrin forms a mesh of fibres and traps platelets and red and white blood cells

Question 3

Which special type of substances/ions are also required for blood clotting?

Answer 3

Vitamin K and calcium ions

Question 4

What are the 3 stages of the cardiac cycle?

Answer 4

Atrial systole
Ventricular systole
Ventricular diastole

Question 5

What do the atria and ventricles do in the atrial systole?

Answer 5

Atria contract

Ventricles relax

Question 6

What do the atria and ventricles do in the ventricular systole?

Answer 6

Atria relax

Ventricles contract

Question 7

What do the atria and ventricles do in the ventricular diastole?

Answer 7

Both ventricles and atria relax

Question 8

How long does the atrial systole last?

Answer 8

0.1 s

Question 9

How long does the ventricular systole last?

Answer 9

0.3 s

Question 10

How long does the atrial diastole last?

Answer 10

0.7 s

Question 11

How long does the ventricular diastole last?

Answer 11

0.4 s

Question 12

Describe the process of atrial systole

Answer 12

The atrial walls contract

Blood flows through the atro-ventricular valves into the ventricles because of the high pressure in the atria

The semi lunar valves are closed so blood can’t go into the pulmonary artery and aorta

Question 13

Describe the process of ventricular systole

Answer 13

The ventricular walls contract

Blood flows through the semi lunar valves into the aorta and pulmonary artery due to the high pressure in the ventricles

The atrioventricular valves shut to prevent backflow of blood into the atria

Question 14

Describe the process of ventricular diastole

Answer 14

The ventricles (and atria) relax

The pressure in the ventricles droop

The semi-lunar valves prevent blood going back into the ventricles

The atrioventricular valves are open and blood flow from the atria into the ventricles

Question 15

How do you calculate heart rate?

Answer 15

60 / length of heart beat

Question 16

Why is there a bump in the ‘atrial pressure curve’ at the start?

Answer 16

This is when the atria contract

Question 17

When do the atrioventricular valves open and how can you see this in a ‘atrial pressure curve’? In which stage of the cardiac cycle does this happen?

Answer 17

When the pressure in the atria starts to get greater than in the ventricles

This happens in the atrial systole

Question 18

When do the atrioventricular valves close and how can you see this in a ‘atrial pressure curve’?

Answer 18

When the pressure in the atria starts to get lower than in the ventricles

This happens in the ventricular diastole

Question 19

Why does the ‘ventricular pressure’ increases slightly in the atrial systole?

Answer 19

Because blood is flowing into the ventricles

Question 20

When does the ‘ventricular pressure’ increase a lot?

Answer 20

During ventricular systole

Question 21

When does the ‘ventricular pressure’ drop?

Answer 21

During ventricular diastole

Question 22

Why does the ‘ventricular pressure’ increase slightly during ventricular diastole?

Answer 22

Because as blood flows into the atria, some blood also flows into the ventricles

Question 23

When do the semi lunar valves open and how can you see this in a ‘ventricular pressure curve’? During which stage does this happen?

Answer 23

When the pressure in the ventricles is greater than in the arteries

This happens in the ventricular systole

Question 24

When do the semi lunar valves close and how can you see this in a ‘ventricular pressure curve’? During which stage does this happen?

Answer 24

When the pressure in the ventricles is smaller than in the arteries (to prevent backflow of blood into the ventricles)

This happens in the ventricular diastole

Question 25

When does the ventricular volume increase to its maximum?

Answer 25

As the atria contract and forcing blood into the ventricles (during atrial systole)

Question 26

When does ventricular volume decrease?

Answer 26

During ventricular systole as blood is being forced out

Question 27

Why does the ventricular volume increase when the heart is in diastole?

Answer 27

Blood flows through the atria and ventricles

Question 28

When is the first heart sound or 'lub' heard? At which stage does this happen?

Answer 28

When the atrioventricular valves close This is the beginning of the ventricular systole

Question 29

When is the second heart sound or 'dub' heard? At which stage does this happen?

Answer 29

When the semilunar valves close This is the beginning of ventricular diastole

Question 30

Why is the heart. muscle myogenic?

Answer 30

It can beat by itself

Question 31

What is the SAN (sinoatrial node)?

Answer 31

It is known as the pacemaker

Question 32

What does AVN stand for?

Answer 32

Atrioventricular node

Question 33

What does RA stand for?

Answer 33

Right atrium

Question 34

What does LA stand for?

Answer 34

Left atrium

Question 35

What does RV stand for?

Answer 35

Right ventricle

Question 36

What does LV stand for?

Answer 36

Left ventricle

Question 37

What sets the heart rate?

Answer 37

How often the SAN sends out an electrical signal

Question 38

Describe the sequence of events that occur during a heartbeat involving the SAN and AVN

Answer 38

1. The SAN sends out electrical impulses causing the atria to contract 2. The electrical impulses are picked up by the AVN 3. After a short delay these impulses are passed on the bundle of His 4. The bundle of His takes the excitation wave to the base of the ventricles 5. The excitation wave passes through the wall to the base of the ventricles causing them to contract

Question 39

What is the bundle of His and where is it located?

Answer 39

Specialised conducting fibres | They are in the wall (septum) between the left and right ventricles

Question 40

What is septum?

Answer 40

Wall

Question 41

Why is the short delay when the electrical impulse are passed on the bundle of His by the AVN so important?

Answer 41

It gives the blood time to flow from the atria into the ventricles and therefore allows the atria to finish contracting before the ventricles contract

Question 42

What is another name for the bundle of His?

Answer 42

Purkinje fibres

Question 43

Why does the excitation wave pass through the wall to the base of the ventricles to make them contract?

Answer 43

To make sure that the ventricles contract from the base upwards forcing the blood up and out of the ventricles into the arteries

Question 44

What are the three things you can get information on from an electrocardiograph (ECG)?

Answer 44

How fast your heart is beating Whether the rhythm of your heartbeat is steady or irregular The strength and timing of electrical signals as they pass through each part of your heart

Question 45

What are the characteristics in an ECG?

Answer 45

The P wave QRS complex T wave

Question 46

What does the P wave in an ECG represent?

Answer 46

The contraction (depolarisation) of the atria

Question 47

What does the QRS complex in an ECG represent?

Answer 47

The contraction (depolarisation) of the ventricles

Question 48

What does the T wave in an ECG represent?

Answer 48

Relaxation (repolarisation) of the ventricles

Question 49

When does the heart muscle depolarise?

Answer 49

When it contracts

Question 50

When does the heart muscle repolarise?

Answer 50

When it relaxes (regains charge)

Question 51

How many electrodes are placed on the chest when an ECG is recorded?

Answer 51

12

Question 52

What is tachycardia?

Answer 52

A heart rate which is too fast

Question 53

What is tachycardia caused by?

Answer 53

``` Exercise Anxiety, pain, fear Hypotension Over-active thyroid Drug effects (stimulants such as caffeine) ```

Question 54

What is hypotension?

Answer 54

Low blood pressure

Question 55

What heart rate is considered tachycardia?

Answer 55

Above 120 bpm

Question 56

What is brachycardia?

Answer 56

A heart rate which is too slow

Question 57

What heart rate is considered brachycardia?

Answer 57

Below 60 bpm

Question 58

What is hypothermia?

Answer 58

High blood pressure

Question 59

What is brachycardia caused by?

Answer 59

``` Drug effects (such as beta blockers) Hypothermia Under-active thyroid Myocardial infarction Electrolyte disorders ```

Question 60

What is myocardial infarction?

Answer 60

A heart attack where the supply of blood to the heart is suddenly blocked by (usually) a blood clot

Question 61

What do beta blockers do?

Answer 61

Block adrenaline

Question 62

What is an electrolyte disorder?

Answer 62

An electrolyte disorder occurs when the levels of electrolytes in your body are either too high or too low

Question 63

What are electrolytes?

Answer 63

Electrolytes are chemicals that conduct electricity when dissolved in water. They regulate nerve and muscle function, hydrate the body, balance blood acidity and pressure, and help rebuild damaged tissue. The electrolytes in human bodies include: ``` sodium potassium calcium bicarbonate magnesium chloride phosphate ```

Question 64

Do fit, athletic individuals have a high or low heart rate?

Answer 64

Slow (brachycardia)

Question 65

What is fibrillation?

Answer 65

Irregular heart beat

Question 66

What causes fibrillation?

Answer 66

When the atria and ventricles lose their rhythm and stop contracting properly

Question 67

What are the consequences of fibrillation?

Answer 67

Chest pain Fainting Lack of pulse Death

Question 68

What is cardiac output?

Answer 68

The volume of blood pumped out by the left ventricle in one minute

Question 69

What is the stroke volume?

Answer 69

Stroke volumeVolume of blood pumped out by the left ventricle

Question 70

How do you calculate cardiac output?

Answer 70

Stroke volume x heart rate