Anti-Arrhythmics intro

Question 1

Membrane potential when Na+ inactivation gates close:

What is the significance?

Answer 1

-75 to -55 mV

***if AP is evoked at -60 mV –> fewer Na+ channels available than if evoked at -80

Question 2

factors that lead to arrhythmias do so by disturbing? (2 things)

Answer 2

1. impulse formation

2. impulse conduction

Question 3

More important phase in determining pacemaker cell impulse formation:

Answer 3

diastolic interval phase 4 ( > action potential; phase 0 and 3)

Question 4

Hyperpolarizing the diastolic interval of the pacemaker cell will _________ pacemaker.

Answer 4

slow

Question 5

Two ways to hyperpolarize pacemaker diastolic interval:

Answer 5

1. vagal discharge (Ach)

2. Beta blockers (inhibit NE)

Question 6

Five ways to speed pacemaker diastolic interval:

Answer 6

1. hypOkalemia
2. Beta stimulation
3. Positive chronotropic drugs
4. fiber stretch
5. acidosis

Question 7

Afterdepolarizations?

Answer 7

Early and delayed

slides 28-30

Question 8

Class I drugs?

Answer 8

Na+ channel blockers

-alter AP duration and kinetics of Na+ channel blockade

Question 9

Class II drugs?

Answer 9

Beta blockers

-blockade of SNS effects in heart

Question 10

Class III drugs?

Answer 10

K+ channel blockers

-prolongation of effective refractory period

Question 11

Class IV drugs?

Answer 11

Ca2+ channel blockers

-slows conduction where depolarization is Ca2+ dependent