Pharm --Heart Phys/Antiarrhythmic Flashcards
This class of antiarrhythmics work on voltage gated Na channels (activated state)
Class 1 – Na channel blockers
This class of antiarrhythmics work on voltage gated K channels
Class 3 – K channel blockers
This class of antiarrhythmics work on voltage gated Ca channels
Class 4 – Ca channel blockers
This class of antiarrhythmics work on sympathetic innervation?
Class 2 – B-blockers
This class of antiarrhythmics work on voltage gated Na channels by depressing phase 0 and proloinging repolarization?
Class 1A
This class of antiarrhythmics work on voltage gated Na channels shortens repolarization?
Class 1B
What parts of the heart exhibit fast-response action potentials?
Myocardium: Atrium, Ventricle, His-Purkinje
What parts of the heart exhibit slow-response action potentials?
SA node, AV node
What heart cells have excitation threshold around:
- -65mV
- -35mV
- -65mV = myocardial cells
- -35mv = nodal cells
How is heart membrane potential affected by:
- -Hypokalemia?
- -Hyperkalemia?
- -HypOkalemia –> hyperpolarizes, increases threshold (more current required)
- -HypERkalemia –> depolarizes, decreases threshold (less current required)
What is normal [K+] range?
3.5mM - 5.5mM
Do the following K+ concentrations Increase or decrease excitability?
- -[K] less than 3.5
- -[K] 5.5-7mM
- -[K] over 7mM
- -[K] less than 3.5 –> increase excitability (but, hyperpolarizes + increase threshold)
- -[K] 5.5-7mM –> increase excitability (decrease threshold)
- -[K] over 7mM –> decrease excitability (but, depolarizes + increase threshold b/c Na current inactivation)
What 3 things are different about an action potential elicited during the relative refractory period?
- -Needs higher than normal stimulus
- -Reduced amplitude
- -Reduced duration
What current determines depolarization in:
- -Myocardium?
- -Nodes?
- -Myocardium = I(Na) – sodium
- -Nodes = I(Ca, L-type) – calcium entering
List the conduction velocities from slowest to fastest
- -Atria
- -AV node
- -His - bundle branch (BB)
- -Purkinje fibers
- -Ventricles
- -AV node –0.05m/s
- -Atria –0.5m/s
- -Ventricles –0.5m/s
- -His-BB –2m/s
- -Purkinje fibers –4m/s
What channel do you block to prevent cardiac contraction
L type Ca+ channel
What measurement is analogous to cardiac preload?
EDV –End diastolic volume
What measurement is analogous to cardiac afterload?
TPR – Total peripheral (vascular) resistance
Sympathetic control of cardiac contractility is by what receptor? What G-coupling?
B1 adrenergic – Gs coupled