cardiac conduction 2

Question 1

P wave =

Answer 1

atrial depolarization

Question 2

QRS =

Answer 2

ventricular repolarization

Question 3

T wave =

Answer 3

T wave =ventricular repolarization

Question 4

PR interval =

Answer 4

index of conduction time across the AV node

Question 5

QT interval =

Answer 5

total duration of depolarization and repolarization

Question 6

The Q is an

Answer 6

initial negative deflection,

Question 7

the R is the

Answer 7

upward deflection

Question 8

the S is a

Answer 8

terminal negative deflection.

Question 9

The sinus node depolarization initiates the

Answer 9

beat but is too small to see

on the ECG.

Question 10

how many separate leads in a ECG?

Answer 10

12

Question 11

the shape of the QRS depends on?

Answer 11

where the positive electrode is placed

Question 12

On EKG, The first signal seen is the

Answer 12

P wave generated by depolarization of first the right and then the left atrium.

Question 13

why is QRS voltage greater than P?

Answer 13

The QRS voltage is much greater than the P voltage because ventricular mass exceeds atrial mass.

Question 14

Why is the T wave wider than QRS?

Answer 14

The T wave is wider than the QRS because ventricular repolarization takes considerably longer than depolarization.

Question 15

why is atrial depolarization not seen?

Answer 15

because normally it s buried in the QRS which is a much larger signal.

Question 16

If the activation wave is \_\_\_\_\_,
a positive (upward) deflection will be recorded

Answer 16

toward a sensing electrode

Question 17

the ____ the muscle mass, the ___ the voltage recorded

Answer 17

greater

greater

Question 18

the pattern of deflection varies with the____

Answer 18

position of the recording electrodes

Question 19

The SA node is high in the ____ and the depolarization wave sweeps _____.

Answer 19

right atrium

downward and leftward.

Question 20

a lead with a positive electrode near the right arm normally has a predominantly ____ QRS

Answer 20

negative

Question 21

a lead with a positive electrode near the left leg has a ____ QRS.

Answer 21

positive

Question 22

normal sequence of activation of the ventricles

Answer 22

1. The upper portion of the septum is depolarized from left to right.
2. There is then depolarization downward in the septum to the apex.
3. Depolarization is from endocardium to epicardium
4. Depolarization moves upward from apex in the free walls of both ventricles.
5. depolarization of the base of the ventricles.

Question 23

SA (sinoatrial node) abnormalities:

Answer 23

cause “sick sinus syndrome” resulting in slow sinus rates or takeover by other pacemakers which may be either fast or slow.

Question 24

3 types of AV block

Answer 24

1st, 2nd, 3rd degree

Question 25

First degree AV block:

Answer 25

conduction delayed but all P waves conduct to the ventricles.

Question 26

2nd degree block:

Answer 26

some P waves conduct but others do not

Question 27

3rd degree block:

Answer 27

none of the P waves conduct & a ventricular pacemaker takes over

Question 28

When the right bundle is blocked,

Answer 28

QRS widening with delayed conduction to the right ventricle

Question 29

When the left bundle is blocked

Answer 29

QRS widening with delayed conduction to the left ventricle

Question 30

When left bundle fascicles are blocked

Answer 30

there are shifts in direction of depolarization but no QRS widening.