cardiac electrophysiology

Question 1

polarization is

Answer 1

resting state of the cells
no deviation from the iso-electric line

Question 2

depolarization is

Answer 2

cells’ state of excitability

Question 3

during depolarization, changes in membrane permeability allow __ ions to cross the cell membrane and enter the cell

Answer 3

Na+

Question 4

movement of NA+ ions causes the inside of the cell to become more __ than outside

Answer 4

electro positive

Question 5

__ represents atrial depolarization

Answer 5

P wave

Question 6

__ represents ventricular depolarization

Answer 6

QRS complex

Question 7

Repolarization is

Answer 7

restoration of the cells to their resting state

Question 8

repolarization is caused by

Answer 8

slower movement of ions leaving the cells

Question 9

movement of __ ions out of the myocardial cells primarily accounts for repolarization

Answer 9

K+

Question 10

___ represents atrial repolarization

Answer 10

Ta wavea

Question 11

___ represents ventricular repolarization

Answer 11

T wave

Question 12

Action potential represents

Answer 12

a full depolarization and repolarization sequence

Question 13

AP of the atrial cells is represented by

Answer 13

P wave

Question 14

AP of the ventricular cells is represented by

Answer 14

QRS

Question 15

Membrane potential (MP) is

Answer 15

the voltage measurement of the cell’s membrane when at rest (polarized)

Question 16

Threshold potential (TP) is

Answer 16

voltage to which a cell must be changed before it can be activated
allows cell to depolarize

Question 17

MP of pacemaker cells is

Answer 17

-40 mV to - 70 mV

Question 18

TP of pacemaker cells is

Answer 18

-35mV to -50mV

Question 19

MP of a non-pacemaker cell is

Answer 19

-90mV

Question 20

TP of a non-pacemaker cell is

Answer 20

-70 to -80mV

Question 21

SA node depolarization and conduction through the atrial is reflected as a

Answer 21

rounded P wave

Question 22

QRS shoots up because

Answer 22

the ventricular cells were resting until they boldly received a stimulus initiating their depolarization

Question 23

phase 4

Answer 23

resting state
iso-electric line

Question 24

phase 0

Answer 24

depolarization
fast Na+ channels then slow Ca++ channels
upward deflection R wave

Question 25

phase 1,2,3

Answer 25

repolarization

Question 26

phase 1

Answer 26

abrupt closure of fast NA+ channels
start of a downward wave (start of S)

Question 27

phase 2

Answer 27

plateau stage of AP
K+ out, slow CA++ still opens

Question 28

open of slow CA++ channels during phase 2 allows :
1.
2.

Answer 28

1. bring more Ca++ for contraction
2. prolong refractoriness by maintaining the cell in a prolonged depolarized state (allows complete contraction before initiate another one)

Question 29

Phase 3

Answer 29

slow Ca++ channels close
increase K+ leaving
negative wave (S wave)

Question 30

absolute refractory period (ARP)

Answer 30

phase 1, 2 and initial part of phase 3

Question 31

ARP corresponds with

Answer 31

QRS and initial part of the ST segment

Question 32

Relative refractory period (RRP) corresponds to

Answer 32

-60mV to -90mV in phase 3
conduction of premature impulses is possible slower than in a fully repolarized cell

Question 33

Vulnerable period

Answer 33

before cell returning to MP(resting)
a weaker stimulus than is normally required (e.g. premature beat) can initiate an AP

Question 34

vulnerable period corresponds with (on ECG)

Answer 34

peak of T wave

Question 35

what’s a “R on T phenomenon”

Answer 35

when an impulse strikes during the vulnerable period