Exam 2 - Arrhythmias Yang

Question 1

put the steps for electrical conduction in the heart in order:

a. excitation spreads down AV bundle
b. AV node fires
c. SA node fires
d. purkinje fibers distribute excitation through ventricular myocardium
e. excitation spreads through atrial myocardium

Answer 1

c, e, b, a, d

Question 2

what does the P wave of ECG show?

Answer 2

atrial contraction

Question 3

what does the QRS complex of an ECG show?

Answer 3

ventricular contraction

Question 4

what does the T wave of an ECG show?

Answer 4

ventricular repolarization

Question 5

what is automacity in regards to pacemaker cells?

Answer 5

they have the ability to generate action potentials regardless of input from outside of the cell (but outside factors for SNS and PNS can change this and have effects on HR)

Question 6

which of these ion channels in the heart is an important one to avoid being targeted when developing new drugs?

a. HCN channels
b. K channels
c. Ca channels
d. Na channels
e. hERG channels

Answer 6

e. hERG channels

Question 7

the inside of the cell is ___ mV and the outside is ___ mV

Answer 7

-70; 0

Question 8

is sodium concentration higher inside or outside the cell?

Answer 8

outside

Question 9

is potassium concentration higher inside or outside the cell?

Answer 9

inside

Question 10

sodium potassium pump how many K and Na are pumped in/out?

Answer 10

3 Na out, 2 K in

Question 11

pacemaker cells exhibit action potentials that are dependent on ___ for the upstroke of the spike

a. Ca2+
b. Na+

Answer 11

a. Ca2+

Question 12

pacemaker cells exhibit action potentials that are dependent on ___ for the upstroke of the spike

a. Ca2+
b. Na+

Answer 12

b. Na+

Question 13

which is FALSE about pacemaker cells?

a. Ca2+ dependent spikes
b. high automaticity
c. contractile cells
d. physiologically depolarized

Answer 13

c. contractile cells (they are specialized, non-contractile cells)

Question 14

which is TRUE about ventricular myocytes?

a. specialized, non-contractile cells
b. hyperpolarized
c. high automaticity
d. Ca2+ dependent spikes

Answer 14

b. hyperpolarized

Question 15

what is phase 3 of the pacemaker action potential?

a. the upstroke
b. repolarization
c. diastolic depolarization

Answer 15

b. repolarization

Question 16

true or false: phase 1 and 2 are not present in the SA node action but is present in Purkinje fiber and myocyte action potentials

Answer 16

true

Question 17

what is phase 0 of the pacemaker action potential?

Answer 17

the upstroke, mediated by Ca2+ channels

Question 18

what is phase 4 of the pacemaker action potential?

a. the upstroke
b. repolarization
c. diastolic depolarization

Answer 18

c. diastolic depolarization

Question 19

what is phase 1 of the myocyte action potential?

Answer 19

it is a brief repolarization, it is the notch at the top of the action potential

Question 20

which current is responsible for phase 1 in myocyte action potentials?

a. INa
b. IKto
c. Ica(L)
d. IK
e. If

Answer 20

b. IKto (“transient outward” repolarizing K+ current)

Question 21

what is phase 2 of the myocyte action potential?

a. upstroke
b. brief repolarization
c. intervening time between APs
d. plateau phase

Answer 21

d. plateau phase (due to mainly Ca2+ currents)

Question 22

true or false: the neuronal action potential involves calcium channels

Answer 22

false

Question 23

three beta blockers used as antiarrhythmics

Answer 23

esmolol
acebutolol
propranolol

Question 24

how do class 2 antiarrhythmics affect the AP diagram?

Answer 24

causes shift to the right (decreases slope of phase 4)

(class 2 are BBs)

Question 25

how do class 4 antiarrhythmics affect the AP diagram?

Answer 25

causes reduced peak (class 4 are CCBs)

Question 26

main clinical use of BBs for arrhythmias

Answer 26

used for arrhythmias involving catecholamines

Question 27

which BB is NOT cardioselective? a. esmolol b. acebutolol c. propranolol

Answer 27

c. propranolol (non-selective)

Question 28

why does esmolol have a very short half life (~9 min)?

Answer 28

due to plasma esterase hydrolysis

Question 29

2 clinical uses of CCBs for arrhythmias

Answer 29

-block re-entrant arrhythmias involving AV node -protect ventricular rate in atrial flutter and A Fib

Question 30

what are class 1 antiarrhythmics?

Answer 30

sodium channel blockers

Question 31

what are class 3 antiarrhythmics?

Answer 31

potassium channel blockers (agents that prolong refractory period)

Question 32

which drug class has a mixed block on Na+ and K+ channels? a. class 1A b. class 1B c. class 1C

Answer 32

a. class 1A

Question 33

which drug class leads to a prolonged QT interval? (also widened QRS) a. class 1A b. class 1B c. class 1C

Answer 33

a. class 1A

Question 34

which drug class has no clinically significant effect on ECG? a. class 1A b. class 1B c. class 1C

Answer 34

b. class 1B

Question 35

which drug class has strong Na+ channel block and a widened QRS complex on ECG? a. class 1A b. class 1B c. class 1C

Answer 35

c. class 1C

Question 36

quinidine, procainamide, and disopyramide are in which class of antiarrhythmics? a. class 1A b. class 1B c. class 1C

Answer 36

a. class 1A

Question 37

lidocaine, tocainide, mexiletine, and phenytoin are in which class of antiarrhythmics? a. class 1A b. class 1B c. class 1C

Answer 37

b. class 1B

Question 38

propafenone, flecainide, and moricizine are in which class of antiarrhythmics? a. class 1A b. class 1B c. class 1C

Answer 38

c. class 1C

Question 39

which class of antiarrhythmics blocks IKr, prolong AP and QT interval, as well as increasing effective refractory period? a. class 1 b. class 2 c. class 3 d. class 4

Answer 39

c. class 3 (K+ channel blockers)