Heartbeat

Question 1

What does SA Node stand for?

Answer 1

Sinoatrial node

Question 2

What is a heartbeat?

Answer 2

A single contraction of the heart

Question 3

What is the ‘lub dub’ of a heartbeat?

2

Answer 3

The contraction of the atria

The contraction of the ventricles

Question 4

How many types of cardiac muscle cells are there?

Answer 4

Two types

Question 5

What are the two types of cardiac muscle cells?

Answer 5

Conducting system (internal wiring)

Contractile cells (muscle)

Question 6

What does the conducting system do?

Answer 6

Controls and coordinates heartbeat

Question 7

What does the contractile cells do?

Answer 7

Produce contractions that propel blood

Question 8

What are the three main types of waves on an ECG trace?

Answer 8

P wave

QRS complex

T wave

Question 9

What does a P wave indicate?

Answer 9

Depolarisation of the atria

Question 10

What does a QRS complex indicate?

Answer 10

Ventricle depolarisation/excitation

Question 11

What does a T wave indicate?

Answer 11

Ventricular repolarisation

Question 12

What does an ECG measure?

Answer 12

Electrical activity of the heart (recorded on the surface)

Question 13

What may an ECG identidy?

Answer 13

An area of tissue damage

Question 14

What is depolarisation?

Answer 14

The signal for excitation

Question 15

What is repolarisation?

Answer 15

The signal for relaxation

Question 16

Why is co-ordinated contraction of the chambers of the heart needed?

Answer 16

To ensure correct timing of blood flow

Question 17

What brings about co-ordinated contraction?

2

Answer 17

The conduction system (internal wiring)

Contractile muscle cells (myofibres)

Question 18

What does AV node stand for?

Answer 18

Atrioventricular node

Question 19

Where does the electrical activity of the heart start?

Answer 19

The pacemaker/SA node

Question 20

What is the pathway for electrical activity in the heart?

5

Answer 20

Pacemaker/SA node

Atrial muscle

AV node (at the same time)

Along conduction pathway in ventricles

Across the ventricle muscle

Question 21

How are muscle cells of the heart interconnected?

Answer 21

They are interconnected at intercalated discs

Question 22

What allows excitation to spread from one muscle cell to another?

Answer 22

Cardiac myofibres

Question 23

What happens when one part of a muscle sheath becomes excited?

Answer 23

All other myofibers in the sheath depolarise

Question 24

What are sheaths of muscle also called?

Answer 24

Syncytia

Question 25

Name the two syncytia of the heart.

Answer 25

Atrial syncytium

Ventricular syncytium

Question 26

Why is a fibrous layer needed between the two syncytia?

Answer 26

To ensure the depolarisation of the atria does not spread to the ventria except at the AV node

Question 27

Why can it be said that the heart tissue uses autorhythmicity

Answer 27

Because the heart tissue contracts rhythmically in the absence of neural and hormonal stimuli

Question 28

List the five parts that make up the conduction system of the heart.

Answer 28

SA node/pacemaker

AV node

Bundle of His

Branch bundles

Purkinje fibres

Question 29

What happens when the excitation reaches the AV node?

Answer 29

There is a delay

Question 30

Why is a delay needed at the AV node?

Answer 30

To allow the atria to contract fully before the ventria depolarise and contract

Question 31

Why is atrial contraction needed first?

Answer 31

To top up the ventria

Question 32

What is an abnormally slow heart rate called?

Answer 32

Bradycardia

Question 33

What is an abnormally fast heart rate called?

Answer 33

Tachycardia

Question 34

What is bradycardia?

Answer 34

Abnormally slow heart rate

Question 35

What is tachycardia?

Answer 35

Abnormally high heart rate

Question 36

What is an ectopic pacemaker?

4

Answer 36

Abnormal cells

Generate high rate of action potentials

Bypass conducting system

Disrupt ventricular contractions