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Flashcards in electrical activity short Deck (15):
1

Resting membrane potential of ventricular myocytes (Em)

-90mV

2

Equilibrium/Nernst potential Ek/na

The membrane potential necessary to stop an ion diffusing down it sconcentration gradient

3

action potential

when membrane potential depolarizes then repolarizes back to resting state, this happens in a wave of electrical discharge that travels along the membrane of an excitable cell

4

Absolute refractory period (ERP)

phase 0,1,2 and part of 3 - cell cannot be excited by a new action potential (h gates still closed)

5

benefit of ERP

limits the frequency of ap's and therefore contractions that the heart can generate so has time to fill and eject blood. stops tetanic contractions

6

relative refractory period

at end of ERP, suprathreshold depoalrization stimuli can elicit ap's. Will have a decreased phase 0 slope

7

sinoatrial node

in posterior wall of right atrium, primary pacemaker site as highest rate

8

overdrive suppression

intrinsic activity of secondary pacemakers suprresssed and they are hyperpolarzied

9

does ecg measure absolute voltage?

no, measures voltage changes from isoelectric baseline

10

verticle and horizontal values on ecg

1mV/cm, 25mm/sec (1 small .04 sec, 1 big .2 second, 5 big is 1 second)

11

Q-Tc calculation

Q-Tc = QT/ square root of RR

12

dromotrophy

conduction velocity, increased by symp, decreased by parasymp

13

threshold

level of depolarization at which a self propagating action potential is generated

14

excitability

Slope and conduction velocity of phase 0. As ap's are initiated later in the relative refractory period of the preceding excitation you get a steeper phase 0 slope, most excitable when resting membrane potenital reached first and phase 0 slope able to return to its steepest

15

irritability

diminished potential between resting and threshold, as irritability increases, depolerization is easier but phase 0 has reduced conduction velocity and gradient