Cardiac Electrophysiology 1

Question 1

equilibrium potential

Answer 1

voltage obtained for a given concentration gradient of a single ion at equilibrium across a semi permeable membrane

Question 2

Gibbs-Donnan equilibrium

Answer 2

special kind of equilibrium involving impermeable polyelectrolyte on one side of a membrane that is permeable to salts but impermeable to the polyelectrolyte

Question 3

diffusion potentials

Answer 3

occur when two or more ions are permeable to a membrane but the various ions have different permeabilities. Examples: cell resting potential, action potentials

Question 4

epithelial membrane potentials

Answer 4

differences of electrical potential that occur between two dilute solutions when the membrane itself is a layer of cells, such as occurs in the kidney and GI systems.

Question 5

raising potassium concentration inside cell

Answer 5

hyperpolarization

Question 6

raising potassium concentration outside cell

Answer 6

depolarization

Question 7

raising sodium concentration inside cell

Answer 7

hyperpolarization

Question 8

raising sodium concentration outside cell

Answer 8

depolarization

Question 9

resting potentials vary among cells because cell membranes have

Answer 9

varying relative permeabilities of sodium to potassium

Question 10

electrodiffusion

Answer 10

process of ions moving through open channels

Question 11

Calcium channel blockers

Answer 11

occludes calcium channel at the extracellular side. reduce both heart rate and contractility of the heart.

Question 12

three state model for voltage gated sodium and calcium channels

Answer 12

closed (resting), open (active), closed (inactive)

Question 13

sodium and calcium channels are outwardly rectifying

Answer 13

low conductances at hyperpolarized voltages but acquire a much larger conductance that enables positive inward currents during the upstroke of the action potential.

Question 14

absolute refractory period

Answer 14

result of the inactivation process. time during which an action potential cannot be initiated, no matter how strong the magnitude of the stimulus.

inactivation gates are mostly still closed so that insufficient inward current is available to reach threshold for another action potential

Question 15

relative refractory period

Answer 15

result of inactivation process, some but not all of the channels have returned to the resting state so that with a large enough stimulus, threshold can be reached and action potential initiated

Question 16

stimulus reaching threshold slowly

Answer 16

results in action potential with a slower rate of depolarization and a smaller magnitude

Question 17

delayed outward rectifier potassium channel is primarily responsible for

Answer 17

the repolarization phase of the action potential. outward rectifier activates upon depolarization but with time delay, permitting a finite duration of the depolarization of the action potential