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ECG Basics and Cardiac Conduction
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ECG Basics and Cardiac Conduction
ECG Basics and Cardiac Conduction
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1
Question
What is the resting membrane potential (RMP) for most cardiac conducting tissues?
Page 1
Answer
-90 mV
2
Question
What primarily mediates depolarization in the SA node and AV node?
Page 1
Answer
Calcium ions (Ca), not sodium (Na)
3
Question
Why is the ECG deflection faster in the ventricles compared to the atria?
Page 1
Answer
Ventricles conduct electrical impulses very fast due to Purkinje fibers.
4
Question
What determines the size of the deflection for atria on ECG?
Page 1
Answer
Small vector due to atrial tissue.
5
Question
What determines the size of the deflection for ventricles on ECG?
Page 1
Answer
Big vector due to larger ventricular tissue.
6
Question
How does the size of cardiac tissue affect ECG deflection strength?
Page 1
Answer
Larger pieces of cardiac tissue produce stronger deflections.
7
Question
Compare the amount of tissue in ventricles versus atria.
Page 1
Answer
Ventricle tissue is larger than atrial tissue.
8
Question
What is the specialized function of the AV node in conduction?
Page 1
Answer
Slow conduction that delays or 'kills' the impulse.
9
Question
Which structures are specialized for fast conduction after the AV node?
Page 1
Answer
Bundle of His and Purkinje fibers.
10
Question
What is the resting membrane potential (RMP) specifically in AV node cells?
Page 2
Answer
-60 mV
11
Question
Why is conduction slower in the AV node compared to other tissues?
Page 2
Answer
Cations move slowly due to RMP of -60 mV.
12
Question
Compare RMP and conduction speed between AV node and fast-conducting tissues.
Page 2
Answer
AV node: RMP -60 mV, slow cation movement; fast tissues: RMP -90 mV, fast cation movement.
13
Question
Why does the ECG not detect activity in the AV node?
Page 2
Answer
Slow conduction makes the heart 'silent' there; current too weak to pick up.
14
Question
How is ventricular septal depolarization characterized on ECG?
Page 2
Answer
Small but fast.
15
Question
Why is left ventricular depolarization bigger than right on ECG?
Page 2
Answer
Left ventricle is larger than right ventricle.
16
Question
What does the P wave represent on an ECG?
Page 3
Answer
Atrial depolarization.
17
Question
According to the notes, what does the PR represent on ECG?
Page 3
Answer
Atrial repolarization.
18
Question
What does the QRS complex represent on ECG?
Page 3
Answer
Ventricular depolarization.
19
Question
What does the ST segment indicate on ECG?
Page 3
Answer
Ventricle totally depolarized.
20
Question
What does the T wave represent on ECG?
Page 3
Answer
Ventricular repolarization.
21
Question
What is the U wave on ECG associated with?
Page 3
Answer
Repolarization of Purkinje fibers.
22
Question
How long does one big square represent on standard ECG paper?
Page 3
Answer
0.2 seconds, equivalent to 5 small squares.
23
Question
How long does one small square represent on ECG paper?
Page 3
Answer
0.04 seconds.
24
Question
What is the duration of the P wave in small squares and seconds?
Page 3
Answer
2 small squares or 0.08 seconds.
25
Question
What is the duration of the PR interval in small squares and seconds?
Page 3
Answer
4 small squares or 0.16 seconds.
26
Question
What is the duration of the QRS complex in small squares and seconds?
Page 3
Answer
2 small squares or 0.08 seconds.
27
Question
What is the duration of the QT interval in small squares and seconds?
Page 3
Answer
10 small squares or 0.4 seconds.
28
Question
How many leads are used in a standard 12-lead ECG?
Page 4
Answer
12 leads.
29
Question
Name the three bipolar limb leads.
Page 4
Answer
I, II, III.
30
Question
What are the three augmented limb leads?
Page 4
Answer
aVR, aVL, aVF.