bioelectric potential Flashcards
equilibrium potential
the voltage necessary to balance a given ionic concentration gradient across a membrane so that the net flux of the ion is zero
nernst equation
used to calculate equilibrium potential
resting potential of K+ when not considering sodium
-58mV
equilibrium potential of K+
-85mV
equilibrium potential of Na+
+ 60 mV
resting membrane potential
-70mV
GHK equation
takes into account the conc of multiple ion species and the permeabilities of all ions
temporal summation
two stimuli in rapid succession coming from the same neuron
spatial summation
two stimuli from different sources
sodium channel gates
activation gate:
voltage dependent, open at threshold and positive feedback (as long as the cell remains depolarised)
inactivation gate: ball and chain
voltage and time dependent, opens following repolarisation where it returns to resting configuration
spike chain
period of time over which cell is producing APs
determined by the amplitude + duration of graded potentials
maximal AP
determined by the refractory period
refractory period types
absolute:
occurs during depolarisation and beginning of repolarisation
2nd AP cannot be generated as Na+ gates are inactivated
period coincides with depolarisation phase
relative:
occurs during repolarisation and hyperpolarisation
2nd AP can be generated with a stronger stimulus
Na+ gates are in resting state
period coincides with hyperpolarisation
high density of sodium channels
trigger zone and nodes of ranvier in myelin sheath
2000 channels vs 2 channels
NT release
is determined by frequency and duration (spike train) of APs not their strength
increase in frequency of AP = more NT’s released
longer the duration of graded potential = longer the time NT’s are released for
