antiarrhythmics (exam 2)

Question 1

arrhythmia

Answer 1

disturbance of electrical signals in the heart to an irregular rate or rhythm

Question 2

how do arrhythmias occur

Answer 2

damage or structural abnormality in tissue
electrolyte abnormality
drugs that can alter cardiac functions

Question 3

symptoms of arrhythmias

Answer 3

palpitations
lightheadedness
syncope
fatigue
cardiac arrest

Question 4

how are arrhythmias classified?

Answer 4

where they originate
how the affect heart rate
type of impulse abnormality

Question 5

location of arrhythmias

Answer 5

atrial (supraventricular)
ventricular

Question 6

effect on HR of arrhytmias

Answer 6

tachycardia
bradycardia

Question 7

type of abnormality of arrhythmias

Answer 7

disturbance of impulse formation (ectopic, EAD, DAD)
disturbance of impulse conduction (heart block, reentry)

Question 8

HCN channels have a key role in ___________________ and are important ________________

Answer 8

controlling cardiac pacemaker activity

regulators of neuronal excitability

Question 9

HCN channels

Answer 9

voltage gated ion channel
dually gated by membrane hyper polarization and cyclic nucleotides

Question 10

funny current (If)

Answer 10

HCN channel in SA node generates this
responsible for spontaneous depolarization that initiates each heart beat

Question 11

what sets the heart rate?

Answer 11

funny current

Question 12

____________ HCN channel expression in enlarged ventricles can contribute to arrhythmias

Answer 12

increased

Question 13

abnormal HCN channel function can lead to

Answer 13

irregular heart rhythms like sinus bradycardia or a-fib

Question 14

which HCN channel is most important in arrhythmias?

why?

Answer 14

HCN4

regulates heart rate and rhythm

Question 15

HCN4 channel

Answer 15

nonselective cation channel
conducts Na and K ions through plasma membrane

Question 16

HCN4 channels generate a ___________________ causing cellular ________________

Answer 16

net inward current (If)

depolarization

Question 17

upon activation by cAMP, there is a ____________ shift of the HCN4 activation curve and If ______________ causing ____________________

Answer 17

positive

increases

cellular depolarization

Question 18

Ivabradine (IVA)

Answer 18

blocks HCN from the intracellular side only
causes cellular hyperpolarization

Question 19

automaticity is due to

Answer 19

leaky Na channels (HCN channels)

Question 20

HCN channels allow for _____________. The threshold potential is

Answer 20

influx of Na (funny current)

-40mV

Question 21

“slow response” actions potentials

Answer 21

nodal APs found in the SA and AV node

Question 22

pacemaker depolarization phase occurs due to

pacemaker depolarization phase occurs due to

Answer 22

Ca2+ influx

K+ efflux

Question 23

myocardial action potential phase 4

Answer 23

at rest (-90mV)

Question 24

myocardial action potential phase 0

Answer 24

depolarization due to Na influx

Question 25

myocardial action potential phase 1

Answer 25

notch due to K efflux

Question 26

myocardial action potential phase 2

Answer 26

plateau due to Ca influx and K efflux

Question 27

myocardial action potential phase 3

Answer 27

depolarization due to K efflux

Question 28

absolute refractory period of myocardial action potential

Answer 28

phase 0 to part of phase 3

Question 29

can you generate an action potential during the absolute refractory period?

Answer 29

no, impossible!

Question 30

relative refractory period

Answer 30

remainder of phase 3

Question 31

can you generate an action potential during the relative refractory period?

Answer 31

yes, but it is difficult

Question 32

refractory period is due to the

Answer 32

inactivation of VG Na channels