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ECG
Overview
15
Anatomy
Undergraduate 1
03/01/2013

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Cards

Term
When does the P wave begin?
Definition
When signal from SA node spreads through atria and depolarises them
Term
What is the PQ segment?
Definition
The time is takes for the impulse to travel from the SA node to the AV node
Term
Describe the appearance of the QRS complex
Definition
Q - small downward deflection
R - tall sharp peak
S - final downward deflection
Term
When does the QRS complex occur?
Definition
When signal from AV node spreads through ventricular myocardium and depolarises muscle
Term
Why does the QRS complex have the shape it does?
Definition
Due to different sizes of two ventricles - i.e. different times to depolarise them
Term
When does ventricular systole begin?
Definition
In the ST segment
Term
Why do atrial repolarisation and diastole, which also occur during QRS, not show on an ECG?
Definition
Weak signal obscured by more muscular ventricles
Term
When does the ST segment occur?
Definition
Plateau in myocardial action potential - time ventricles contract and eject blood
Term
What generates the T wave?
Definition
Ventricular repolarisation immediately before diastole
Term
To ventricles take longer to depolarise or repolarise?
Definition
Repolarise
Term
What effect does that fact that ventricles take longer to repolarise than depolarise have on the shape of the T wave compared to the QRS complex?
Definition
T wave smaller and more spread than QRS and has rounder peak
Term
What part of an ECG shows ventricular repolarisation?
Definition
T wave
Term
What part of an ECG shows when the signal from the AV node spreads through ventricular myocardium and depolarises them?
Definition
QRS complex
Term
What part of an ECG shows the times it takes for the impulse to travel from the SA node to the AV node?
Definition
PQ segment
Term
What part of an ECG shows when the signal from the SA node spreads through the atria and depolarises them?
Definition
P wave
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