Cardiac Electrophysiology

Question 1

What are the 7 conduction pathways through the heart?

Answer 1

1) SA node (normal pacemaker)
2) Intranodal tracts (controversial)
- AV nodal tract
- Bachmann’s bundle to LA
3) AV node
4) Bundle of His
5) Bundle Branches
6) Purkinje fibers
7) Ventricular muscle

Question 2

what is the relationship of the component of the ECG w/ the mechanical events in the heart?
P-Wave

Answer 2

Atrial depolarization

Question 3

what is the relationship of the component of the ECG w/ the mechanical events in the heart?
PR interval

Answer 3

Atrial Systole and AV nodal delay

Question 4

what is the relationship of the component of the ECG w/ the mechanical events in the heart?
QRS complex

Answer 4

ventricular depolarization (atrial depolarization)

Question 5

what is the relationship of the component of the ECG w/ the mechanical events in the heart?
QT interval

Answer 5

Ventricular systole

Question 6

what is the relationship of the component of the ECG w/ the mechanical events in the heart?
T wave

Answer 6

Ventricular repolarization

Question 7

Action potential with a PLATEAU phase are found where?

Answer 7

Atrial muscle cells

Ventricular muscle cells

Question 8

Action potentials arising om the SA node and AV node are biphasic. what does that mean?

Answer 8

they have a depolarization and depolarization phase with no plateau phase.

Question 9

what is the RMP of the cardiac ventricular cell?

Answer 9

-90 mV

Question 10

What are the phases of the ventricular action potential.

Phase 4

Answer 10

Resting membrane potential (diastole)

Question 11

What are the phases of the ventricular action potential.

Phase 0

Answer 11

Rapid depolarization
Na+ diffuses into cell
AKA the upstroke of the potential

Question 12

What are the phases of the ventricular action potential.

Phase 1

Answer 12

Transient (breif) repolarization
Cl- influx
K+ Efflux

Question 13

What are the phases of the ventricular action potential.

Phase 2

Answer 13

Plateau
Ca+ influx
(as always K+ efflux)

Question 14

What are the phases of the ventricular action potential.

Phase 3

Answer 14

Repolarization

K+ Efflux

Question 15

What are the phases of the ventricular action potential. 
Phase 4 (last phase 4)

Answer 15

RMP
(diastole)
Na+ / K+ pump operates to restore intracellular Na+ and K+ to appropriate levels

Question 16

See page 103 in sweat book for diagram

Answer 16

pg 103 sweat book

Question 17

What are the phases of the SA or AV nodal action potential?

Phase 4

Answer 17

RMP (Diastole)
Spontaneous depolarization to threshold
K+ efflux
Na+ influx
Ca++ influx (during last 1/3 of phase)

Question 18

What are the phases of the SA or AV nodal action potential?

Phase 0

Answer 18

SLOW depolarization
Ca++ and Na+ diffuse into cell
(side note it is the L-type Ca+ channels aka slow Ca++ channels thus the reason it is slow depolarization)

Question 19

What are the phases of the SA or AV nodal action potential?

Phase 1

Answer 19

Gotcha there is no phase 1

Question 20

What are the phases of the SA or AV nodal action potential?

Phase 2

Answer 20

Gotcha again with nodal action potential there is no phase 1 and phase 2

Question 21

What are the phases of the SA or AV nodal action potential?

Phase 3

Answer 21

Repolarization

K+ Efflux

Question 22

What are the phases of the SA or AV nodal action potential?

back to phase 4

Answer 22

RMP (diastole)

Question 23

R/T the action potential of the SA node….. changing the rate of what phase leads to a change in HR?

Answer 23

Phase 4

Question 24

R/T the action potential of the SA node prolonging the phase 4 does what?

Answer 24

slows HR

Question 25

R/T the action potential of the SA node shortening the Phase 4 dose what?

Answer 25

increases HR

Question 26

then next questions teach you to read the question closely.... pay attention to nodal action or ventricular action potentionals.

Answer 26

read carefully

Question 27

on what phase of the NODAL ACTION potential does digitalis work to SLOW the HR?

Answer 27

Phase 4 | - Dig slows the HR by slowing phase 4 depolarization of cells in the SA and AV node

Question 28

on what phase of the NODAL ACTION potential do CCB's work to SLOW the HR

Answer 28

Phase 4 | - CCB slow HR by slowing phase 4 depolarization of cells in the SA and AV node

Question 29

on what phase of the NODAL ACTION potential does Lidocaine or phenytoin work to control VENTRICULAR dysrhythmias?

Answer 29

Phase 4

Question 30

to recap why these drugs work on phase 4

Answer 30

in the NODAL action potential Ca++ is in phase 4 there is no plateau phase as with the ventricular action potential

Question 31

on what phase of the VENTRICULAR ACTION POTENTIAL do CCB's work?

Answer 31

Phase 2 | Plateau phase

Question 32

The resting membrane potential of the cardiac ventricular cell is what?

Answer 32

-90 mV

Question 33

What ion is responsible for establishing the transmembrane resting potential

Answer 33

K+

Question 34

When the gated Na+ channel is in the inactive state ( phase 2), the cardiac cell is in the ____ _____ period?

Answer 34

absolute refractory period

Question 35

an influx of what ion causes the ventricular cell to produce a plateau in phase 2 of the action potential?

Answer 35

Ca++

Question 36

Ca++ ions influence the opening of the gated K+ channel, with Hypocalcemia what happens to the duration of the plateau phase?

Answer 36

prolong

Question 37

Ca++ ions influence the opening of the gated K+ channel, with Hypercalcemia what happens to the duration of the plateau phase?

Answer 37

shortened

Question 38

on an ECG tracing each mm corresponds to how many seconds?

Answer 38

0.04 seconds

Question 39

The QRS complex results from what and what phase?

Answer 39

Ventricular depolarization | Phase 0

Question 40

The T wave results from what? and what phase?

Answer 40

Ventricular repolarization | phase 3

Question 41

the QT interval reflects the duration of what phase of the action potential?

Answer 41

Plateau phase (2)

Question 42

with HYPOcalcemia what happens to the QT interval?

Answer 42

it is prolonged

Question 43

with HYPERcalcemia what happens to the QT interval?

Answer 43

it is shortened

Question 44

peaked or tented T waves reflect what K+ problem?

Answer 44

Hyperkalemia

Question 45

U waves reflect what K+ problem

Answer 45

Hypokalemia

Question 46

what leads indicate Posterior inferior MI and what coronary artery supplies it?

Answer 46

II, III, aVF | Right (RCA)

Question 47

which leads indicate septal, anterior wall MI? and what coronary artery supplies it?

Answer 47

V2-V5 | Left Anterior Descending (LAD)

Question 48

which leads indicates a lateral wall MI? and what coronary artery supplies it?

Answer 48

I, aVL, V4 - V6 | Left Circ

Question 49

MAP is determined by what 2 factors?

Answer 49

CO | SVR

Question 50

CO is determined by what 2 factors?

Answer 50

HR | SV

Question 51

SV is determined by what 3 factors?

Answer 51

Preload Afterload Contractility

Question 52

Preload is determined by what 2 factors?

Answer 52

``` IV volume Venous tone ( when veins constrict blood is diverted to the heart, and vice versa) ```

Question 53

The major determinant of IV volume is the amount of what in the body?

Answer 53

Sodium

Question 54

what hormone is most important for controlling vascular volume

Answer 54

Aldosterone

Question 55

Compared with the normal heart, the size of the left ventricle chamber is NOT changed what what type of hypertrophied heart?

Answer 55

concentric

Question 56

Compared with the normal heart, the size of the left ventricle chamber IS substantially increased what what type of hypertrophied heart?

Answer 56

Eccentric