ECG

Question 1

Conducting system of the heart=

Answer 1

The heart contains specialised non-contractile cells that can generate APs. These cells are known as cardiac pacemaker cells.

Question 2

What is the key conduction pathway?

Answer 2

1- Sinoatrial node (SA) initiates every heartbeat.
2- Impulse then flows to atrioventricular (AV) node.
2- Sends impulse down AV bundle
3- This bundle splits to allow impulse to flow down L+R bundle branches.
4- These bundle divide into purkinje fibres that are able to conduct cardiac AP more quickly than other cells of the heart so it can get to all areas of the heart efficiently.

Question 3

Describe the AP of contractile muscle cells

Answer 3

1- Depolarization= sodium gated ion channels open.
2- Plateau phase= myocardium contracts, calcium ions enter
3- Repolarization= potassium channels open, potassium exits.
4- Refractory period

Question 4

ECG=

Answer 4

Test to record electrical signals in heart.
As electrical impulses reach the surface of the body they are detected and cause deflections (waves) on ECG tracing. They are P wave, QRS wave and T waves.

Question 5

Explain the wave forms on an ECG

Answer 5

• P wave is atrial depolarisation
• QRS is ventricular depolarisation
• T wave is ventricular repolarisation

Question 6

Fibrous annulus=

Answer 6

Slows electrical signal down to make conduction system work more efficiently

Question 7

What is the heart rate regulated by?

Answer 7

Autonomic nervous system

Question 8

What is the average resting heart rate?

Answer 8

72 b.min

Question 9

Tachycardia=

Answer 9

High Hr, over 100b.min

Question 10

Bradycardia=

Answer 10

Low Hr, below 60b.min

Question 11

Arrhythmia=

Answer 11

Abnormal heart rhythm

Question 12

Artificial pacemaker=

Answer 12

Is used if the SA node is not acting as it should. So pacemaker can initiate the heart beat.