Yang Flashcards
what is the order of electrical conduction in the heart?
SA node fires
excitation spreads through atrial myocardium
AV nodes fires
excitation spreads down AV bundle
purkinje fibers distribute excitation through ventricular myocardium
what is hERG?
an important channel to avoid being targeted when developing new drugs
KCNH2, KV11.1
how much K is in and out of the cell?
in 148 mM
out 5 mM
how much Na is in and out of the cell?
in 10 mM
out 142 mM
how much Ca is in and out of the cell?
in under 1 uM
out 5mM
how much Cl is in and out of the cell?
in 4mM
out 103 mM
what is the average membrane potential in the cell?
-70 mV
usually negative
how much is the normal membrane potential outside of the cell?
0 mV
which way does K move according to each gradient?
electrical gradient - OUT
concentration gradient IN
how does Na move according to each gradient?
electrical - OUT
concentration - OUT
what drives depolarization of cardiac cells (phase 0)?
increased Ca2+
increased Na+
what signals phase 1?
Na+ channels closing
what signals Phase 2?
increased Ca2+
decreased K+
what signals rapid repolarization (Phase 3)?
Ca2+ channels closing
decreased K+
what signals resting potential (phase 4)?
leaky K+ channels
what is the absolutely refractory period?
a 2nd action potential cannot be initiated
what are pacemaker cells dependent on?
CA2+ spikes
what is ventricular myoctes dependent on?
Na spikes
before Ca spikes, where do pacemaker cells sit on mV?
-50 mV
what does iF mean on a chart?
diastolic pacemaker current
shows phase 4
what does PKA do in a cell?
phosphorylates other channels and makes them easier to open
how does iNa impact myocyte action potential?
carries AP upstroke
phase 0
how long is recovery from inactivation?
20 msec to > 10 sec
what is the order of rest, open, inactivated for channel control?
rest then open then inactivated then rest again
