Lecture 12- ECG

Question 1

How does atrial fibrillation affect ECG?

Answer 1

P wave will be altered as it triggers atrial depolarisation

May also get QRS complexes different distances apart

Question 2

SA node location?

Answer 2

Junction of right atrium and SVC

Question 3

AV node location?

Answer 3

In inter-atrial septum near tricuspid valve

Question 4

Purpose of fibrous ring/skeleton of heart?

Answer 4

Acts as an insulator to delay conduction between atria and ventricles giving atria time to contract fully

Question 5

SA node rate?

Answer 5

60-100 sinus rhythm

Question 6

What does ECG record?

Answer 6

Electrical changes on extracellular surface of cardiomyocytes

Question 7

What happens when the cell is depolarised?

Answer 7

Outside becomes negative relative to the inside.

If it moves towards positive electrode will give an upward deflection

Question 8

What happens to cell when repolarised?

Answer 8

Outside will become more positive relative to inside. If towards positive electrode will give downward deflection but as repolarisation happens in opposite direction upward deflection occurs.

Repolarisation more prolonged and gives more of a curve

Question 9

Viewing electrical activity from different views?

Answer 9

Electricity heading directly towards electrode gives greatest deflections and perpendicular the smallest ones

Question 10

Atrial depolarisation and ecg?

Answer 10

Gives small upward p wave deflection and lasts 80-100ms

Question 11

What happens at AV node in ECG?

Answer 11

Fibrous ring means signal stopped and get a flat line (isoelectric)