Lecture 7 Starting at Vectors Flashcards Preview

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Flashcards in Lecture 7 Starting at Vectors Deck (31)
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1

A ________ is an arrow that points in the directionof the electrical potential generated by the _______ flow, with the arrowhead in the _______ direction

Vector
Current
Positive

2

Axis for lead I (both arms), what do the following equal?
R-arm = ?
L-arm = ?
Direction of Lead = ?

R = negative
L = positive
Direction of lead = 0 degrees

3

Axis for lead II (r-arm and l-leg), what do the following equal?
Arm = ?
Leg = ?
Direction of Lead = ?

Arm = negative
Leg = positive
Direction of Lead = 60 degrees

4

Axis for lead III (l-arm and l-leg), what do the following equal?
Arm = ?
Leg = ?
Direction of Lead = ?

Arm = negative
Leg = positive
Direction of Lead = 120 degrees

5

When is the voltage recorded in the ECG very low?

when the vector in the heart is in a direction almost perpendicular to the axis of the lead

6

What happens when the heart vector has almost the same axis as the axis of the lead?

The entire voltage of the vector will be recorded

7

What do we call the summated vector of the generated potential at a particular instant?

Instantaneous mean vector

8

With respect to the base of the heart, the apex of the heart remains ______ as a result of the depolarization wave through the ventricles

Positive

9

What is the mean electrical axis of the heart?

59 degrees
The direction of the electrical potential (- to +) from the base of the ventricles toward the apex

10

In T-waves, what is the greatest portion of ventricular mass to repolarize first?

The entire ouster surface, especially near the apex

11

In T-waves, what areas normally repolarize last?

Endocardial

12

In T-waves, where is the ventricular vector during repolarization?

Towards the apex of the heart

13

Is the normal T-wave in all three bipolar leads positive or negative?

Positive

14

In the P-wave, where does atrial depolarization begin?

Sinus node

15

In the P-wave, what direction is the atrial vector generally in?

In the direction of the axes of the three standard bipolar limb leads

16

P-wave ECG is normally _____ in all three leads

positive

17

In atrial T-wave, is the spread of depolarization through the atrial muscle faster or slower than in the ventricles?

Slower

18

In the atrial T-wave, what is the first part to become repolarized?

Sinus node

19

What is different about each lead?

Each lead provides a different perspective on the voltage differences between areas of the heart

20

Name abnormal ventricular conditions that cause axis deviation (5):

Change in position of heart in the chest
Hypertrophy of one ventricle
Bundle branch block
Fluid in pericardium
Pulmonary emphysema

21

High-voltage ECG is said to occur when the sum of the voltages of all the QRS complexes of the three standard leads is greater than ____

4 mV

22

What is the most common cause of High-Voltage ECG?

Hypertrophy of the ventricle

23

What causes decreased voltage in the standard bipolar leads?

Cardiac myopathies
Conditions surrounding the heart

24

How long does a normal QRS last?

0.06 to 0.08 seconds

25

How long may a QRS be prolonged in hypertrophy or dilation of the left or right ventricle?

0.09 to 0.12 seconds

26

What conditions cause bizarre complexes?

Destruction of cardiac muscle and replacement by scar tissue
Multiple small local blacks in the conduction impulses at many points in the Purkinje system

27

Define Currents of Injury

Different cardiac abnormalities cause part of the heart to remain partially or totally depolarized all the time

28

What abnormalities cause current of injury?

Mechanical trauma
Infectious processes
Ischemia (most common cause)

29

What is the effect of current of injury on QRS complex?

Abnormal negative current flows from infarcted area and spreads toward the rest of the ventricles

30

What is the name of the reference point for analyzing current of injury?

J point