EKG Ch. 1

Question 1

What does the EKG record?

Answer 1

The electrical activity of the heart through specialized terminals called electrodes

Question 2

What is the beginning of the electrical cascade in the heart?

Answer 2

Stimulation of the individual myocytes

Question 3

What are the specialized areas of conducting cells in the heart?

Answer 3

• Sinus node
• Atrioventricular (AV) node
• Bundle of His
• Bundle branches

Question 4

What happens to the myocardial cells during depolarization?

Answer 4

They gain a positive charge, causing them to contract

Question 5

What term refers to the process of cardiac cells regaining a negative resting charge?

Answer 5

Repolarization

Question 6

What does the P wave on the EKG represent?

Answer 6

Atrial depolarization

Question 7

What does the QRS complex on the EKG represent?

Answer 7

Ventricular depolarization

Question 8

What do the ST segment and T wave on the EKG represent?

Answer 8

The entirety of ventricular repolarization

Question 9

What determines whether an EKG complex appears upright or downright?

Answer 9

The flow of electricity toward (upright or positive) or away (downright or negative) from the area of the myocardium it represents

Question 10

What is the term for the ability of cells to initiate a pacemaker impulse?

Answer 10

Automaticity

Question 11

Where are automaticity foci (cells that generate a pacemaker impulse) located?

Answer 11

• Sinus node
• AV node
• Ventricles

Question 12

What is the normal firing rate of the sinus node?

Answer 12

60 to 100 beats per minute (bpm)

Question 13

What does a normal P wave on the EKG look like?

Answer 13

Monophasic, entirely positive or negative

Question 14

Where is the AV node located?

Answer 14

In the interatrial septum near the coronary sinus

Question 15

What is the normal intrinsic firing rate of the AV node?

Answer 15

40 to 60 bpm

Question 16

What is the significance of the bundle of His?

Answer 16

Connects electrical signals from the AV node to the ventricular bundle branches

Question 17

What do the bundle branches consist of?

Answer 17

• Right bundle branch
• Left bundle branch (which is further divided into left anterior fascicle and left posterior fascicle)

Question 18

What is represented by the QRS complex on the EKG?

Answer 18

Electrical activity through the bundle branches

Question 19

True or False: The electrical activity from the bundle of His is reflected on the EKG by a specific interval.

Answer 19

False

Question 20

Fill in the blank: The area of impulse-generating tissue located in the high right atrium is known as the _______.

Answer 20

Sinus node

Question 21

What happens if the sinus node fails to generate an impulse?

Answer 21

The AV node can generate an impulse at a slower rate

Question 22

What does the term ‘infra-hisian’ refer to?

Answer 22

A block originating distal to the bundle of His

Question 23

Explain depolarization and repolarization.

Answer 23

1. Cardiac cells have negative resting internal charge
2. Positive charge spreads from sinus node through the myocardium to initiate contraction
3. When the myocardial cells gain a positive charge, they contract
4. Cells are then repolarized after electrical conduction ends, resulting in negative resting charge

Question 24

Define the EKG complexes.

Answer 24

1. P wave represents atrial depolarization
2. QRS complex represents ventricular depolarization
3. ST segment and T wave represent ventricular repolarization

Question 25

Identify the anatomy of the conduction system.

Answer 25

1. Sinus node 2. AV node 3. Bundle of His 4. Bundle branches 5. Perkinje fibers

Question 26

Describe the sinus or sinoatrial (SA) node and its function.

Answer 26

1. Located in the high right atrium 2. Conducts slightly faster than competitors; setting the pace for conduction (60 to 100 bpm) 3. Visualized on an EKG as the P wave 4. Normal sinus has a positive P wave 5. A negative P wave (or low atrial focus) indicate the SA failed to initiate a timely electrical impulse; resulting in the impulse being conducted lower in the atrium

Question 27

Describe the atrioventricular (AV) node and its functions.

Answer 27

1. After SA impulse, conduction moves through both atria toward the AV node 2. Located in the interatrial septum and is the electrical connection between the atria and the ventricle 3. Conduction slows here to allow the tricuspid and mitral vales to open; allowing the ventricles fill with blood prior to systole 4. Visualized on an EKG as the PR interval 5. If SA fails, the AV node will initiate the electrical cascade at a slower rate (40 to 60 bpm) 6. The absence of P waves and heart rate between 40 to 60 bpm is indicative of a junctional rhythm

Question 28

Describe the bundle of His and its function.

Answer 28

1. Located distal to the AV node 2. Conducts electrical signals from the AV node to ventricular bundle branches 3. Not directly visualized on an EKG 4. Anatomical marker in identifying the location of a block (i.e. second-degree type I versus second-degree type II)

Question 29

Describe the bundle branches and their functions.

Answer 29

1. Divided into the right bundle branch and the left bundle branch 2. The left bundle branch is further divided into the left anterior fascicle and the left posterior fascicle 3. Branches comprise rapidly conducting fibers, known as Purkinje fibers 4. The right bundle branch goes down the interventricular septum, terminating at the apex 5. The left bundle branch goes down the interventricular septum; then divides into the fascicles, terminating at the apex 6. Visualized on an EKG as the QRS complex