Cardiac Cycle

Question 1

Does the pulmonary or systemic circulation have a higher pressure?

Answer 1

Systemic

Question 2

Which structure is responsible for venous drainage of the heart?

Answer 2

Coronary sinus

Question 3

What drains into the coronary sinus?

Answer 3

Left ventricle, most epicardial ventricular veins

Question 4

Stages of heartbeat 1) 2) 3) 4) 5)

Answer 4

1) Late diastole 2) Arterial systole 3) Isometric ventricular contraction 4) Ventricular ejection 5) Isometric ventricular relaxation

Question 5

What are the only part of venous and arterial vessels that run parallel in the same direction?

Answer 5

Coronary sinus, circumflex artery

Question 6

When does left coronary flow mostly occur?

Answer 6

Diastole

Question 7

Why does left coronary flow occur mostly during diastole?

Answer 7

Difference in pressure between aorta and left ventricle During systole there is no such difference

Question 8

What is the rate of SA node pacemaker?

Answer 8

~70 beats/minute

Question 9

What is the rate of AV node autorhythmicity?

Answer 9

~50 beats/minute

Question 10

What is the rate of Purkinje fiber autorhythmicity?

Answer 10

25-40 betas/minute

Question 11

How does the SA node communicate with the AV node?

Answer 11

Internodal pathways through the right atrium

Question 12

Electrical conduction in heart

Answer 12

1) SA node 2) Internodal pathways 3) AV node 4) AV bundle 5) Bundle branches 6) Purkinje fibers

Question 13

What does the ECG measure?

Answer 13

Whole heart average extracellular potential (from the body surface) Depolarisation either towards or away from electrodes

Question 14

What are the ECG electrodes connected to in Einthoven’s triangle?

Answer 14

Left leg Right arm Left arm

Question 15

What is isovolumetric contraction/relaxation?

Answer 15

1) Function of elastic wall of heart 2) Contraction of ventricles with no corresponding change in volume 3) When intraventricular pressure doesn’t exceed the pressure in aorta –> aortic valve doesn’t open

Question 16

Is diastole passive?

Answer 16

No. ATP required to pump Ca from smooth muscle cytoplasm

Question 17

How do the ventricles fill with blood?

Answer 17

25% from atrial contraction 75% passively during diastole

Question 18

Stroke volume

Answer 18

Amount of blood injected each time the heart contracts

Question 19

Does the nervous system regulate SA depolarisation?

Answer 19

Yes Regulated by the autonomic nervous system

Question 20

Why do Purkinje fibers conduct AP to base of heart first?

Answer 20

So that the base of the heart contracts first This prevents blood being trapped in the heart

Question 21

Do myocardial cells summate graded potentials?

Answer 21

No Long refractory period prevents this

Question 22

What are the waves in an ECG?

Answer 22

1) P wave 2) QRS complex 3) T wave

Question 23

What is the P wave?

Answer 23

Atrial depolarisation

Question 24

What is the QRS complex?

Answer 24

Ventricular depolarisation

Question 25

What do the different parts of the QRS complex represent?

Answer 25

1) Q - Depol of bundle of His, Purkinje fibers 2) R - Depol of bottom of ventricles 3) S - Depol of the upper part of ventricles

Question 26

When do the ventricles contract on an ECG?

Answer 26

In the period directly after the S wave

Question 27

When do the atria contract on an ECG?

Answer 27

In the period directly after the P wave

Question 28

What is the T wave?

Answer 28

Repolarisation of the ventricles

Question 29

What is the ST segment?

Answer 29

Depolarisation of the ventricles

Question 30

What will an ECG look like it the leads are placed 180 degrees in the opposite direction?

Answer 30

A mirror image

Question 31

Is there electrical activity elsewhere in the heart during the QRS complex?

Answer 31

Yes, but these deflections are overwhelmed by the left ventricle

Question 32

What is the standard ECG today?

Answer 32

9 electrodes, 12 leads

Question 33

How is a modern ECG represented?

Answer 33

4 lines: First 3 lines are the 12 leads (3 rows by 4 columns) Bottom line is the long arm of lead 2, which shows the rhythm of the heart

Question 34

What results in a positive ECG reading?

Answer 34

Electrical activity towards the positive electrode

Question 35

What are the three intervals of an ECG?

Answer 35

PR QRS QT

Question 36

Atrial fibrillation

Answer 36

Erratic atrial activity Not linked to SA node pacemaking Normally 1 P wave per QRS complex. This is not the case in atrial fibrillation

Question 37

Possible causes of atrial fibrillation

Answer 37

Idiopathic electrolyte imbalance Dilated atria Sympathetic hyperactivity

Question 38

Ventricular fibrillation

Answer 38

Ventricles beat independently of the atria Less common than atrial fibrillation, much more serious No obvious pattern to ECG

Question 39

Possible causes of ventricular fibrillation

Answer 39

Ischaemia in heart attack Electrocution

Question 40

How to restore normal rhythm from ventricular fibrillation

Answer 40

Defibrillator (electric shock)

Question 41

Does the diastolic pressure in the aorta fall more quickly or slowly than in the ventricles?

Answer 41

More slowly It feeds to into smaller vessels (capillaries)

Question 42

When do valves close?

Answer 42

When the pressure in the current compartment exceeds that in the previous compartment

Question 43

What can be heard and not heard from the heart?

Answer 43

Can hear turbulent flow Can't hear laminar flow

Question 44

Heart sounds 1) 2)

Answer 44

1) Atrioventricular valves closing 2) Semilunar valves closing

Question 45

Which heart action corresponds with the sound of the atrioventricular valves closing?

Answer 45

Ventricular contraction

Question 46

Which heart action corresponds with the sound of the semilunar valves closing?

Answer 46

Ventricular relaxation

Question 47

What does a noise when the valves are open indicate?

Answer 47

A defect in the valves Non-laminar flow

Question 48

Measurements depicted on a Wigger's diagram

Answer 48

1) ECG 2) Heart pressure 3) Heart sounds 4) Left ventricular volume

Question 49

Average time between P waves

Answer 49

~800msec

Question 50

What does the dicrotic notch represent?

Answer 50

Closure of the aortic or pulmonary valve

Question 51

Answer 51

Question 52

When does artrial systole occur relative to ECG?

Answer 52

After P wave

Question 53

When does ventricular ejection occur relative to ECG?

Answer 53

After QRS complex

Question 54

When does the left ventricle fill relative to ECG?

Answer 54

QRS complex