Cardiac Conduction System / ECG

Question 1

Describe the position of the SA node:

Answer 1

Right atrial wall near superior vena cava

Question 2

Describe the position of the AV node:

Answer 2

The triangle of Koch, located in the Interatrial septum

Question 3

Describe the position of the bundle of His:

Answer 3

Interventricular septum

Question 4

Describe the position of the purkinje fibres:

Answer 4

Endocardium near apex of the heart

Question 5

What is the function of the SA node?

Answer 5

Generates electrical impulses to begin contraction of the heart

Question 6

Which part of the nervous system controls the rate of the SA node?

Answer 6

The autonomic nervous system

Sympathetic and Parasympathetic

Question 7

What effect does the sympathetic nervous system have on the SA node?

Answer 7

Makes SA node generate impulses faster, speeding up heart rate

Question 8

What is the function of the AV node?

Answer 8

Delays the signal generated by the SA node by a a fraction of a second

Question 9

Why is the AV node important?

Answer 9

To ensure the atria are empty of blood before contraction stops

Question 10

What effect does the parasympathetic nervous system have on the SA node?

Answer 10

Makes SA node generate impulses slower, decreasing heart rate

Question 11

What is the function of the left His bundle branch?

Answer 11

Sends electrical signals through the Purkinje fibers to your left ventricle

Question 12

What is the function of the His bundles?

Answer 12

To relay the impulse from the AV node to the Purkinje fibres

Question 13

What is the function of the purkinje fibres?

Answer 13

Deliver electrical signals to the ventricles causing ventricular systole

Question 14

What is the function of the right His bundle branch?

Answer 14

Sends electrical signals through the Purkinje fibers to your right ventricle

Question 15

Where is the cardiovascular centre located?

Answer 15

Medulla oblongarta

Question 16

What factors may influence the rate of SA node impulse generation?

Answer 16

Age
Sex
Emotion
Exercise
Medication

Question 17

What causes valves to open?

Answer 17

Pressure gradients

Question 18

How does contraction affect the pressure in a heart chamber?

Answer 18

Contraction increases pressure

Question 19

What causes the first heartbeat sound (S1)?

Answer 19

The closing of the atrioventricular valves

Question 20

What causes the second heartbeat sound (S2)?

Answer 20

The closing of semilunar valves

Question 21

Define cardiac output:

Answer 21

The volume of blood pumped out of each ventricle per minute

Question 22

Define stroke volume:

Answer 22

The volume of blood leaving the ventricles per contraction

Question 23

Define heart rate:

Answer 23

The number of heart beats occurring in one minute

Question 24

What is the relationship between cardiac output, stroke volume and heart rate?

Answer 24

Cardiac output = Stroke volume x Heart rate

Question 25

A stroke volume of 60ml and a heart rate of 80bpm, what would the cardiac output be?

Answer 25

4800ml

Question 26

What is ejection fraction?

Answer 26

The percentage of blood in a ventricle which is removed in a contraction

Question 27

If a ventricle is filled with 100ml of blood and 62ml leaves the aorta after contraction, what is the ejection fraction?

Answer 27

62%

Question 28

What is the end-diastolic volume (EDV)?

Answer 28

The blood in the ventricle at the end of diastole (pre-contraction)

Question 29

What is the relationship between Stroke volume, ESV and EDV?

Answer 29

Stroke volume = EDV - ESV

Question 30

What is the end-systolic volume (ESV)?

Answer 30

The blood in the ventricle at the end of systole

Question 31

An ESV of 40ml and EDV of 100ml would mean the stroke volume is what?

Answer 31

60ml

Question 32

Define preload?

Answer 32

The degree of stretch of cardiac myocytes at the end of ventricular diastole

Question 33

What is an ECG / EKG

Answer 33

A tracing of the overall electrical activity of the heart

Question 34

What are the different phases seen on an ECG?

Answer 34

``` P (atrial systole) PR segment QRS complex (ventricular systole) Ventricular diastole T ```

Question 35

Explain what happens during phase P on an ECG:

Answer 35

The impulse causes muscle cells in the atria to depolarise and contract, resulting with atrial systole

Question 36

Explain what happens during the PR segment on an ECG:

Answer 36

The impulse reaches the AV node

Question 37

Explain what happens during the QRS complex on an ECG:

Answer 37

The impulse moves down the bundle of his to the purkinje fibres causing ventricular systole

Question 38

Explain what happens after the QRS complex on an ECG:

Answer 38

Ventricular walls start to relax and recover, this is ventricular diastole

Question 39

What is the QT Interval on an ECG?

Answer 39

The time it takes for depolarisation and repolarisation of a ventricle to occur

Question 40

What happens in phase T of an ECG?

Answer 40

Repolarisation of the ventricles

Question 41

If there is a problem with the atria which part of the ECG will change?

Answer 41

The P wave

Question 42

``` The rhythmic beating of the heart is initiated by what structure? A. Purkinje fibres B. Bundle of His C. AV node D. SA node E. Right ventricle ```

Answer 42

D. SA node

Question 43

``` The T wave on an ECG represents what? A. Ventricular depolarisation B. Ventricular repolarisation C. Atrial depolarisation D. Atrial repolarisation E. Ventricular systole ```

Answer 43

B. Ventricular repolarisation

Question 44

Which of the following pairs is mismatched? A. Stroke volume is the volume of blood pumped during each heartbeat B. Blood pressure is the force blood exerts against a blood vessel wall C. Heart rate is the number of times the heart beats per minute D. CO = HR x SV E. Cardiac output is the volume of blood which passes through the heart in one heart beat

Answer 44

E. Cardiac output is the volume of blood which passes through the heart in one heart beat

Question 45

When does ventricular ejection occur?

Answer 45

When the ventricular pressure is sufficient enough to open the semilunar valves