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14 Cards in this Set

  • Front
  • Back
Where is the SA node?
In the superior RA at the junction with the SVC
True/False: The atrium and the ventricles are insulated from each other
TRUE--the only electrical connection is the AV node
How does the Bundle of His relate to the purkinje fibers? Where does one begin and another end?
The bundle of His and the fascicles end in purkinje cells that are distributed all across the endocardial surface of the heart
Can purkinje cells contract?
YES--they are myocytes but have poorly developed contractile machinery
Describe how all cardiac cells have the following properties: Automaticity, excitability, conductivity, contractility, and conductivity
Think about it
What cells have a Slow AP?
SA Node and AV Node
What are the most important membrane related processes in the heart?
DIFFUSION VIA CHANNEL PROTEINS, primary active transport, and counter transport
How is calcium transported in the heart?
Via the L type and T type transporters
At the beginning of a fast AP, what causes permeability to K?
IK1--inwardly rectified K channel causing the membrane potential at baseline to be close to the Nernst potential
What is the Nernst Potential with regards to membrane electrical signaling?
Point at which the diffusion potential opposes further movement of the ions in spite of the concentration gradient = no further movement of ions
What happens when the transmembrane voltage of a cardiac cell is slowly depolarized? Where does this happen? What effect does it have?
Inactivation of the channels occurs without the initial opening and current flow--as long as this partial depolarization exists, the closed, inactive ion channels cannot recover to resting state and won't transport Na+ ions--this is found in the SA and AV nodes--their membrane voltage is generally less negative than -70 mV at all times and fast sodium channels don't play a part in generation of AP here
At rest, the membrane of cardiac cells is most permeable to what?
Potassium--inward rectifier channels conduct potassium out of the cell--the ions are also pulled back in by negative charge inside so the potassium EQ potential is set up at -91mV
From phase 0 to phase 4, what is the predominate ion that is moving?
Phase 0: Na+ Phase 1: K+ outward Phase 2: balance of outward K+ and inward Ca++ Phase 3: K+ outward Phase 4: K+ (and slightly Na+) maintains EQ potential at -90 mV
What is the maximum negative potential of pacemaker cells?
-60 mV causing the fast sodium channels to remain inactivated