Lecture 5

Question 1

Define and explain the concept of overdrive suppression as it applies to the normal and latent pacemakers of the heart

Answer 1

• In the event the SA node fails, we have the latent pacemakers that can take over, the AV node can take over and do this and if both fail, the purkinje fibers can take over. You can only have 1 king at a time. The SA node is the quickest and results in the fastest HR (AV is slower and Purkinje is even slower)

Question 2

Basic ECG (3-lead)

Answer 2

1- 4 electrodes
2- One on each arm
3- Ground on right leg
4- electrode on left leg

Question 3

Lead 1

Answer 3

1- LA

2- RA

Question 4

Lead 2 (most common)

Answer 4

1- RA

2- LL

Question 5

Lead 3

Answer 5

1- LA

2- LL

Question 6

12- lead ECG

Answer 6

10 electrodes:
6 precordial (chest) electrodes
V1 - V6

4 limb electrodes (RA, LA, RL, LL)
give 6 views: I, II, III, aVL, aVF and aVR

Question 7

P wave

Answer 7

depolarization of atria

Question 8

QRS complex

Answer 8

depolarization of ventricles

Question 9

T wave

Answer 9

Depolarization of the ventricles

Question 10

PQ segment

Answer 10

time when the impulses is traveling through the AV node, bundle of His, and bundle branches

Question 11

PR interval

Answer 11

onset of P wave to middle of QRS complex

Question 12

ST segment

Answer 12

end of QRS complex to onset of T wave

Question 13

ST Interval

Answer 13

end of QRS complex to end of T wave

Question 14

QT interval

Answer 14

onset of QRS complex to end of T wave

Question 15

Latent pacemakers

Answer 15

1- AV node
2- Purkinje Fibers
-may exhibit automaticity and override the SA node if it is suppressed

Question 16

Intrinsic rate of phase 4 depolarization (and heart rate)

Answer 16

is fastest in the SA node and slowest in the purkinjie fibers