Antiarrhythmics Flashcards
Why do sodium, potassium, and calcium need channels?
net + charge so can’t move readily across phospholipid bilayer
What opens or closes ion channel gates?
specific transmembrane conditions such as voltage, ionic, or metabolic
What is the path of cardiac conduction?
SA node->Internodal tracts->AV node->bundle of His->L&RBB->purkinje fibers
What are 3 ways you can alter HR?
1)rate of phase 4 depolarization, 2)threshold potential, 3)RMP
What’s the intrinsic rate of the SA node?
70-80bpm
What’s the intrinsic rate of the AV node?
40-60bpm
What’s the intrinsic rate of the purkinje fibers?
15-40 bpm
Define arrhythmias.
those electrical impulses or cardiac depolarization that deviate from the normal pathway. Abnormalities in site of origin, rate/regularity, or conduction pathway
What regulates the RMP?
potassium
Most cells are impermeable to ________ at rest but highly permeable at the start of an action potential.
sodium
What happens at phase 0 of a ventricular action potential?
gates open, Na enters, fast depolarization. brief.
What happens phase 1-2 of a ventricular action potential?
Repolarization starts, Cl- in, K out (phase 1) Na stops influx, Ca moves in, K moves out (phase 2). slow development of repolarization (K+)
What happens phase 3 of a ventricular action potential?
fast repolarization, Na and Ca minimum influx, K moves out, end of phase 3 cardiac cells respond to stimulus greater than normal intensity (relative refractory period)
What happens phase 4 of a ventricular action potential?
resting potential, repolarized state, diastole, Na/K pump: 3Na out for 2K in to keep negative
What’s resting membrane potential for ventricular?
-90
What’s threshold potential for ventricular?
-70-
When’s the absolute refractory period?
phase 1-3ish
Is sodium higher inside or outside cell?
outside…flows in
Is potassium higher inside or outside of cell?
inside….flows out
Is Calcium higher inside or out of cell?
outside…flows in
What determines HR?
SA node/autonomic tone, rate of phase 4 depolarization
What’s the RMP for nodal action potential?
-60
What’s the threshold potential for nodal action potentials?
-45
What happens phase 0 of nodal action potential?
t-type Ca channels open so further depolarization/tips scales, Ca in, Na in, depolarization