Intro to Electrophysiology

Question 1

What cardiac structure supports valves, separates atria and ventricles and electrically insulates atria from ventricles (electrical impulses must travel through conduction pathways)?

Answer 1

Cardiac skeleton

Question 2

BP = __ x __ ?

Answer 2

BP = CO x PVR

Question 3

The SNS acts via beta receptors to have what type of effects?

Answer 3

Cardioaccelerator effects

Question 4

When is the SNS activated by the cardioregulatory center to release NE/ Epi, increase HR and contractility, constrict peripheral blood vessels, and increase CO and BP?

Answer 4

BP too low

Question 5

The PNS acts via the vagus nerve to have what type of effects?

Answer 5

Cardioinhibitory effects

Question 6

When is the PNS activated by the cardioregulatory center to release ACh, decrease HR and decrease BP?

Answer 6

BP too high

Question 7

What type of cells are contractile cells?

Answer 7

Myocardial cells

Question 8

What myocardial cell structure permits conduction of impulses longitudinally from one cell to the next?

Answer 8

Gap junctions in intercalated disks (connection point)

Question 9

What myocardial cell strucutre surrounds the cardiomyocyte, preventing lateral signal transduction?

Answer 9

Sarcolemma

Question 10

Myocardial cells contract as a unit and are held together by what?

Answer 10

Desmosomes

Question 11

What are the 4 key properties of myocardial cells?

Answer 11

Automaticity, excitability, conductivity, contractility

Question 12

What myocardial cell property is defined as the ability of certain cells to produce an electrical impulse without outside nerve stimulation?

Answer 12

Automaticity

Question 13

What myocardial cell property is defined as the ability to respond to an electrical stimulus?

Answer 13

Excitability

Question 14

What myocardial cell property is defined as the ability to transmit an electrical stimulus from cell to cell?

Answer 14

Conducivity

Question 15

What myocardial cell property is defined as the ability to contract when electrically stimulated?

Answer 15

Contractility

Question 16

What state of myocardial cells consists of negatively charged ions insie and positively charged ions outside?

Answer 16

Polarized state (resting state)

Question 17

The difference in charges in the resting state of a myocardial cell results in what?

Answer 17

RMP (no net ion flow)

Question 18

During an action potential, what ion movement results in depolarization?

Answer 18

Na+ quickly into cell and Ca slow (leads to positive charge inside cell)

Question 19

During an action potential, what ion movement results in repolarization?

Answer 19

Na, Ca, K out of cell

Question 20

Following depolarization, temporary resistance to further depolarization is defined as what?

Answer 20

Absolute refractory period

Question 21

What keeps the depolarization wave moving forward and prevents spasms of continued contraction in one area?

Answer 21

Absolute refractory period

Question 22

Period of time duing the late phase of repolarization in which only a strong electrical stimulus will cause depolarization is defined as what?

Answer 22

Relative refractory period

Question 23

What type of cells have the ability to spontaneously generate an impulse (depolarize) at a certain rate?

Answer 23

Pacemaker cells

Question 24

What is the pathway of conduction in the heart? (5)

Answer 24

SA node → AV node → bundle of His → R&L bundle branches → purkinje fibers

Question 25

What is the primary pacemaker?

Answer 25

SA node

Question 26

What is the intrinsic rate of the SA node and what ion drives it?

Answer 26

60-100 bpm, Na driven

Question 27

What heart structure is a pathway for impulses to reach ventricles and slows the signal to allow atria to contract and empty as much blood as possible into the ventricles for stronger contraction and improved CO?

Answer 27

AV node

Question 28

What is the intrinsic rate of the AV node and what ion drives it?

Answer 28

40-60bpm, Ca driven

Question 29

What structures are located on either side of the IV septum?

Answer 29

R and L bundle branches

Question 30

Left bundle branches split into what?

Answer 30

Ant and post fascicles

Question 31

What heart structures are the terminal branches of the R and L bundle branches that spread throughout the myocardium?

Answer 31

Purkinje fibers

Question 32

What is the intrinsic rate of the Purkinje fibers?

Answer 32

20-40bpm

Question 33

What type of cells carry electrical impulses to appropriate regions of the heart?

Answer 33

Electrical conducting cells

Question 34

Which leads are bipolar?

Answer 34

Limb leads I, II, III

Question 35

Unipolar leads consist of what?

Answer 35

Only positive electrode + reference point

Question 36

Which leads are unipolar?

Answer 36

Chest/ precordial leads (V1-V6), augmented limb leads

Question 37

Which leads provide frontal plane views? Horizontal plane views?

Answer 37

• Limb leads = frontal plane views = einthoven’s triangle (leads I, II, III, aVR, aVL, aVF)
• Chest (precordial) leads = horizontal plane views (leads V1-V6)

Question 38

What is the difference between vectors and axis?

Answer 38

Vectors = many small electrical currents in various directions, overall direction of sum of vectors = axis

Question 39

Movement towards (+) electrode produces what?

Answer 39

Mark above baseline

Question 40

Movement towards (-) electrode (or away from (+)) produces what?

Answer 40

Mark below baseline

Question 41

Movement perpendicular to (+) electrode produces what?

Answer 41

Biphasic waveform

Question 42

What ECG element represents atrial depolarization?

Answer 42

P wave

Question 43

What ECG element represents ventricular depolarization?

Answer 43

QRS wave

(atrial repolarization hidden in QRS wave)

Question 44

What ECG element represents ventricular repolarization?

Answer 44

T wave