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NSG 531 EXAM 3; LATEST UPDATES
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Phases of action potential in non-pacemaker cells. Phase 0 involvesdepolarization.
Phase 1 involves partial repolarization.
Phase 2: plateau.
Phase 3: Repolarization
Phase 4: RMP.
ANSWER Phases of action potential in pacemaker cells. Phase 0 involves fast
depolarization.
Phase 3: Repolarization
Phase 4 involves gradual depolarization.
When do nonpacemaker action potentials imitate or change into pacemaker
action potentials? - ANSWER In hypoxic conditions
Three main reasons of abnormal cardiac rhythm - ANSWER 1: Heart block
2. Ectopic Pacemaker
3. After-depolarizations.
ANSWER: The main reasons of heart block are Typically caused by ischemia in
the conducting system, namely in the AV node.
Can also result from fibrosis.
The main causes of ectopic pacemakers are ischemia or catecholamines.
The most common causes of after-depolarizations - ANSWER The most
common cause is increased intracellular calcium, which causes aberrant action
potentials.
Linked to hypercalcemia, high catecholamines, and heart failure.
How do after-depolarizations manifest? - ANSWER Ectopic beat, premature
contractions, extrabeats, extrasystole, or tachycardia.
, Manifest as tachyarrhythmia.
There are two approaches to repair after-depolarizations. - ANSWER Calcium
channel blockers
Beta-blockers
Sodium/calcium exchange pump ratio - ANSWER 3:1: 3 sodium injected in and
1 calcium pumped out.
Sodium/potassium pump ratio - Answer: 3 sodium for 2 potassium.
Needs energy.
There are four classes of anti-arrhythmic medicines. - ANSWER I: sodium
channel blockers II: beta-adrenergic blockers.
III: potassium channel blockers.
Calcium channel blockers (IV)
Effects of class I (sodium channel blockers) on the action potential - ANSWER
Prolonged depolarization (EXCEPT FOR CLASS 1B)
3 class 1A drugs: ANSWER Disopyramide
Quinidine Procainamide
ANSWER Intermediate kinetics for class IA medicines.
Effects of class 1A medicines on action potential: ANSWER Slow
depolarization.
Prolong depolarization and refractory time.
Class 1B medications include lidocaine, tocainide, and mexiletine.
Kinetics of Class 1B Drugs - ANSWER FAST
The impact of class 1B medicines on action potential - ANSWER: No
prolongation of the refractory period and no lengthening of the duration of the
action potential.
No effect on phases 0 or 1.
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