ECGs

Question 1

How is a heart able to conduct an action potential?

Answer 1

The heart consists of specialised heart muscle that is able to initiate and conduct cardiac impulses

Question 2

Why does the heart conduct an action potential?

Answer 2

The impulses allows the heart to pump blood through the atria and ventricles and into pulmonary and systemic circuits

Question 3

How do ECGs work?

Answer 3

The impulses are small electrical currents that travel through the body to the surface and can be detected by an electrocardiograph

Question 4

What are the 4 stages of action potentials of contractile cardiac muscle cells?

Answer 4

1. Depolarisation
2. Plateau phase
3. Repolarisation
4. Refractory period

Question 5

What is depolarisation?

Answer 5

Depolarisation (the stimulus) causes a response in the muscle cell, which is the contraction of that cell.

Depolarisation of one cell can be the stimulus for depolarisation of the adjoining cells and so a wave of contraction passes through the cells.

Question 6

What is repolarisation?

Answer 6

Repolarisation is the depolarised cell returning to the resting position and getting ready for the next contraction

Question 7

What prevents an impulse from passing directly from the atria to the ventricles?

Answer 7

Fibrous annulus

Question 8

What is arrhythmia?

Answer 8

An abnormal heart rhythm

Question 9

What causes myocardial infarction?

Answer 9

Insufficient blood flow to the heart muscle from narrowing of coronary artery may cause chest pain

Question 10

What are characteristics of a myocardial infarction on an ECG?

Answer 10

ST segment elevation over area of damage
ST depression in leads opposite infarction

Pathological Q waves
Reduced R waves
Inverted T waves