SFOS 11

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Author:
zf2010
ID:
79915
Filename:
SFOS 11
Updated:
2011-04-16 02:27:36
Tags:
Cardiac Electrophysiology
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Description:
SFOS 11
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  1. What channels are responsible for resting permeability of cardiac membrances?
    Non-gated leakage channels (Na, K)
  2. Types of cardiac action potentials
    • Ventricular, Atrial
    • Nodal
  3. Describe phases of ventricular A.P.
    Phase 4 - iK1 (voltage-gated K channels) are open

    Phase 0 - Fast Na channels open due to depolarization, Na rushes in

    Phase 1 - Brief repolarization due to closing of Na channels, Ito1 (voltage-gated K channel) opens briefly

    • Phase 2 - Plateau
    • iK1 plugged with Mg++
    • iCa (voltage-gated Ca channel) opens slowly, Ca enters cell

    • Phase 3 - Repolarization
    • iCa closes
    • K channels open
  4. Describe the phases of Nodal A.P.
    • Phase 0 - depolarized by pacemaker potential
    • iCa slowly opens, Ca enters cell, closes at peak

    Phase 1 - not present

    Phase 2 - not present

    • Phase 3 - Repolarization
    • iK opens

    • Phase 4 - Pacemaker potential
    • K channels close at max repolarization
    • Resulting depolarization opens iCaT (Ca enters cell, depolarizes it)
    • iF (Na channel) opens, depolarizes cell
    • These currents bring to threshold
  5. What is the mechanism and effect of Vagal effects?
    • Parasympathetic - uses Acetylcholine
    • Decreases Na permeability in Nodal phase 4
    • Decreases Ca permeability in Nodal phase 0
    • Increases K permeability
    • Slows the heart rate
  6. Mechanism and effect of sympathetic effects
    • Uses Norepinephrine
    • Increases Na, Ca permeability
    • Decreases K permeability
    • Increases heart rate
  7. What is the sum of all cardiac myocyte vectors?
    Mean cardiac vector

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