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
what is re-entry arrhythmia?
when ischemic damage in the lower part of the heart blocks it from traveling to separate ventricles leading to a re-entrant circuit
how does BB affect mV?
shifts the whole graph to the right
example of class 2
how do Ca2+ channel blockers affect mV?
example of class 4
decreases the peak and shifts it to the right
what drug is the main BB to know for antiarrhythmias?
esmolol
what drugs are the main CCB for antiarrhythmias?
verapamil
diltiazem
how do CCB block re-entrant arrhythmias?
involve the AV node and prevent it from reaching peak
how does quinidine affect action potential?
class 1a
prolonged QT leading to similar graph but inactive period extends further to the right
how does lidocaine and mexiletine affect action potential?
not clinical significant on ECG so graph looks the same
class 1B drugs
how does flecainide affect action potential?
strong Na+ channel block so it widens QRS; changes slope of graph to be more 1/1 rather than up and down
class 1c drug
how do class 3 drugs affect action potential?
block Ik to prolong duration and QT interval
increases effective refractory period
what is amiodarone?
class 3 antiarrhythmic
top choice for rate control in Afib, suppression of post MI ventricular arrhythmias
what genetic mutations cause acquired long QT syndrome?
KCNQ1
KCNH2
SCN5a
how do the different subclasses of class 1 affect Na+?
1a - moderately
1b - weak
1c - strong
what are the main class 5 anti arrhythmic drugs?
digoxin
adenosine (brief but potent)
what class causes widen QRS?
1c
what class increases PR?
1a
