Cardiac Ion Channels & Action Potentials Flashcards
Explain ectopic pacemakers.
Ectopic pacemakers are cells other than those in the sinoatrial node that determine the heart rate; this is bad, and often occurs after damage to myocardium.
Which two areas of the heart conduct action potentials slowly?
The sinoatrial node and the atrioventricular node; ventricular muscle, atrial muscle, and Purkinje’s fibers conduct fast.
If Vm
current flows into the cell
If Vm > Eion, then ____________.
current flows out of the cell
What is DHPR?
Dihydropyridine receptor, a voltage-gated calcium channel
Phase 4 is not steady-state, but rather ________.
a continuous, gradual depolarization
What produces repolarization in both skeletal and cardiac muscle action potentials?
Ik
Ik is made by ___________.
the HERG gene; this is often tested as a possible side effect before drugs go to studies
The AV node also has spontaneous pacemaking ability, but ____________.
it is slower than the SA node, so it doesn’t control the heart’s beating unless something is wrong with the SA node
Ifunny channels are inactivated at _______ potentials and activated at __________.
depolarized; hyperpolarized
Ifunny channels are permeable to both _______ ions.
sodium and potassium
In terms of potassium efflux, ________ open first then _________.
I(transient outward); Ik and Ir
Phase 0 is _________.
rapid influx of sodium and calcium
Phase 1 is ___________.
partial repolarization due to inactivation of sodium channels and activation of I(to) channels
Phase 2 is characterized by ___________.
competition between the L-type calcium channels and the delayed rectifier potassium channels
