Membranes and constants Flashcards
what is the resistor-capacitor (RC) model
bilayer is capacitor
ion channels = resistor
what are three mechanisms we need to explain passive conduction
final (stable) voltage at V0
attenuation of final stage voltage with distance
delay in voltage response relative to current stimulus time
how do we determine final stable voltage
ohms law = V=IR
what is attentuation of final voltage with distance
amplitude decreases as moves from stimulus site
what can be used for attenuation of final voltage
space (length) constant - lambda and this describes how rapidly voltage drops
what is definition of space constant
distance at which voltage is 1/3 of original value
what is a consequence of larger lambda
longer means that passive signals go further before they fade away- more spatial summation
what are three ways to prevent attenuation/increase space constant
higher membrane resistance
glial wrapping
fatter axons
what do fatter axons have larger space constants
internal resistance decreases with diameter squared
so internal resistance decreases when increase diameter
what is the time constant
voltage change with an exponential time course- time it takes to get to 1/3 of final value
what is an ion flux
if membrane not at equilibrium, ion experiences driving force to move it across membrane
what is the ion flux equation
i=g(em-eeq)
what are three factors of leakage channels
always open
low conductance
unchanging
