Exam 2 Week 1- Anti-arrhythmic Agents Flashcards
Phase 0 (Cardiac Cell)
rapid depolarization (fast sodium channels open; fast inward flow of Na+)
Phase 1 (Cardiac Cell)
beginning of repolarization (sodium channels close)
Phase 2 (Cardiac Cell)
plateau (slow calcium channels open; slow inflow of Ca2+)
Phase 3 (Cardiac Cell)
repolarization (calcium channels close; potassium channels open; slow outward K current)
Phase 4 (Cardiac Cell)
pacemaker potential; returning to resting membrane potentials
Refractory period (Cardiac Cell)
phases 1-3
periods of repolarization
Phase 0 (SA/AV Node)
upstroke
critical firing threshold (-40mV)
slower and Ca2+ mediated
Phase 3 (SA/AV Node)
repolarization
inactivation of Ca2+ and Na+ channels
activation of K channels
Phase 4 (SA/AV Node)
gradual depolarization
slow inward Na and Ca2 currents
What node is the cardiac pacemaker?
Sino-atrial
Normal sinus rhythm is
60-100bpm
Which node conducts more slowly then the SA?
AV node
Which node conducts faster then the AV node?
Purkinje fibers
P wave indicates
Atrial depolarization
QRS complex represents
ventricular depolarization
T wave represents
ventricular repolarization
What is an arrhythmia
is the disturbance in the electrical activity of the heart
Classification of arrhythmia
site of origin of abnormality (atrial/junctional/ventricular)
complexes on ECG
Heart Rhythm (regular/irregular)
Heart rate is increased or decreased
Mechanisms of arrhythmia production
Altered automaticity
delayed after-depolarization
re-entry
conduction block
Altered automaticity
latent pacemarker cells take over the SA node’s role; escape beats
Delayed after-depolarization
normal action potential of cardiac cell triggers
Re-entry
refractory tissue reactivated repeatedly and rapidly due to unidirectional block, which causes abnormal continuous circuit
Conduction Block
impulse fail to propagate in non-conducting tissue
Supraventricular Drugs
adenosine IV
digoxin
verapamil