Class 9

Question 1

What is the phenomenon of pacemaker cells with higher intrinsic rhythm preventing latent pacemakers in the heart from firing

Answer 1

Overdrive Suppression

Question 2

Pacemaker cells with higher intrinsic rhythm tend to suppress what?

Answer 2

Latent pacemaker’s automaticity

Question 3

When is the automaticity of pacemaker cells depressed?

Answer 3

When they are forced to fire faster than their intrinsic rate

Question 4

What is the mechanism of overdrive suppression?

Answer 4

The activity of the Na/K ATPase increased when Na has a higher rate of influx, creating a higher rate of Na efflux than K influx

Question 5

When overdrive suppression has happened it is more (negative, positive) in the cell

Answer 5

Negative, hyperpolarization

Question 6

When it is more negative in the pacemaker cell, what happens to the pacemaker’s automaticity?

Answer 6

It is suppressed

Question 7

When a pacemaker cell is hyperpolarized, the diastolic potential is changed how?

Answer 7

More negative maximum diastolic potential

Question 8

When a pacemaker cell is hyperpolarized, what happens to the threshold value?

Answer 8

It is increased, thus slowing automaticity

Question 9

What is a phenomenon that cardia impulses may re-excite the myocytes through which it had passed previously within same cardia cycle?

Answer 9

The re-entry loop

Question 10

What is a direct consequence of conduction disturbance?

Answer 10

Onset of tachycardia or fibrillation

Question 11

3 essential conditions required for the re-entry loop:

Answer 11

1) Must be closed conduction loop
2) Must be region of unidirectional block
3) Slow conduction of impulse around the loop

Question 12

What does the re-entry loop cause physically to happen?

Answer 12

An extra heart beat

Question 13

SA node controls the cardiac rhythm describes what?

Answer 13

Sinus rhythm

Question 14

Sinus rhythm with a rate less than 60 bpm describes what?

Answer 14

Sinus bradycardia

Question 15

Sinus rhythm with a rate greater than 100 bpm describes what?

Answer 15

Sinus tachycardia

Question 16

Defined as the onset of abnormal heart rhythms is what?

Answer 16

Arrhythmia

Question 17

Prolonged impairment of SA node allows latent pacemaker (AV node) to initiate escape beat is what?

Answer 17

Escape rhythm

Question 18

Continuation of escape beats gives ride to what?

Answer 18

Escape rhythm

Question 19

What is more sensitive to parasympathetic activity? SA and AV nodes or ventricular conducting system

Answer 19

SA and AV nodes

Question 20

What is the ventricular conduction system?

Answer 20

bundle of His or bundle branches

Question 21

During intense parasympathetic activity what becomes the latent pacemaker? When would this happen?

Answer 21

Ventricular conduction system, this is an escape rhythm

Question 22

In intense parasympathetic activity, is the HR high or low?

Answer 22

Low

Question 23

Ischemia of the SA node can trigger what?

Answer 23

Onset of junctional escape beat and thus junction rhythm

Question 24

What is an ectopic beat?

Answer 24

A heartbeat generated by impulse other than from the SA node

Question 25

Junctional escape beat is a form of what?

Answer 25

Ectopic beat

Question 26

Impulse from latent pacemaker travels in two driections:

Answer 26

1) Towards the ventricular contractile myocytes 2) Towards the atrial contractile myocytes

Question 27

What happens to an ECG when there is an impulse from a latent pacemaker in junctional escape rhythm?

Answer 27

Inverted P wave

Question 28

What happens to ECG when impulse from a latent pacemaker in a ventricular escape rhythm?

Answer 28

Absent QRS complex

Question 29

What is an absent QRS complex an indication of?

Answer 29

An AV block

Question 30

When the AV node is blocked, what is the latent pacemaker?

Answer 30

bundle of His or bundle branches

Question 31

Ventricular tachycardia on a ECG:

Answer 31

Normal ECG, but fast heart rate, may have a wider QRS complex

Question 32

What can ventricular tachycardia lead to?

Answer 32

Ventricular flutter (over 200 bpm)

Question 33

What can ventricular flutter lead to?

Answer 33

Ventricular fibrillation

Question 34

What is ventricular fibrillation?

Answer 34

Form of nonfunctional muscle contraction, produces no cardiac output

Question 35

Impaired conduction through the AV conduction system describes what?

Answer 35

Heart block

Question 36

What is included in the AV conduction system?

Answer 36

AV node, bundle of His, bundle branches

Question 37

Delay between atrial and ventricular depolarization is what degree of heart block?

Answer 37

First

Question 38

Intermittent failure of AV conduction is what degree of heart block?

Answer 38

Second

Question 39

First degree heart block on ECG:

Answer 39

Prolong PR interval

Question 40

What are the symptoms of a first degree heart block?

Answer 40

Usually asymptomatic, could get worse

Question 41

What are the 2 types of second degree heart blocks?

Answer 41

1) Mobitz I - Wenckebach 2) Mobitz II

Question 42

Mobitz I second degree heart block on ECG:

Answer 42

PR interval progressively lengthens until one QRS complex is absent, repeats

Question 43

What are the symptoms of Mobitz I second degree heart block?

Answer 43

AV node problem, increased vagal tone

Question 44

Mobitz II second degree heart block on ECG:

Answer 44

QRS complex absent every few PR intervals, may lose two or more in a row

Question 45

What is often the cause of Mobitz II second degree heart block?

Answer 45

Septal infarct or His-Purkinje system degeneration

Question 46

Third- degree heart block on ECG:

Answer 46

Total dissociation between P wave and QRS complex

Question 47

What can cause a third degree heart block?

Answer 47

Myocardial infarction or degeneration of the AV conduction system

Question 48

Complete hear block with complete failure of conduction between atria and ventricles is what degree of heart block?

Answer 48

Third

Question 49

Symptoms of third degree heart block?

Answer 49

Low HR, light headedness

Question 50

Occurs when the electrical impulse from the bundle of His does not conduct along the right bundle branch is what?

Answer 50

Right bundle branch block

Question 51

In a right bundle branch block what happens to the right ventricle?

Answer 51

The right ventricle depolarizes later and is slower

Question 52

Occurs when transmission of impulse is delayed or fails along the main left bundle branch or in both left anterior and posterior fascicles is what?

Answer 52

Left bundle branch block

Question 53

In left bundle branch block, what happens to the left ventricle?

Answer 53

The left ventricle depolarizes slowly by cell-to-cell conduction that spreads from right v to left v