neurophysiology for neurotransmitters part 1: excitability Flashcards
what is the current model of the cell membrane?
fluid mosaic model
what are channels
gated aqueous pores
the gates control whether ions can transverse pore.
what does a channel respond to?
gating stimulus (ie transmembrane volatage, binding of ligand, temperature, mechanical distortion of membrane)
what is part of the channel that determines which ions can move through the channel
selectivity filter
what do internal binding site in channel allow for?
internal binding site allow modulation of channel function by signalling pathways
what is current?
movement of charge
what carries charge in biological systems?
ions
what is a circuit element that resists charge?
resistor
relationship of conductance and resistance?
conductance = reciprocal of resistance
what is OHM’s Law?
V = IR
where V = voltage
I = current
R = resistance
what is equation for resistance?
Resistance = 1/G; G = conductance
what is a circuit element that can store charge?
capacitor
ion channels = what part of RC circuit
resistive elements (conductors of ions)
lipid bilayer = what part of RC circuit
insulator (cf dielectric of capacitor: stores charge= capacitance)
passive response = RC circuit
what is the consequence of the RC structure
electrical signals slowed by the capacitor(b/c it stores charge) —> membrane with time constant (time for membrane potential to fall to 1/e of original potential charge)
what does it mean if membrane semipermeable to ions?
permeable to some ions and not others
which ion are cells permeable to at rest?
K+
what maintains differen concentrations of the principal ion species?
what is membrane potential usually?
Na+/K+ ATPase
-70mV
if the membrane potential were only permeable to a single species, which equation would you use to find the equillibrium potential for that ion species?
Nernst equation: Eion = 61 log ([ion]outside/[ion]inside)
which equation predicts which ion species is dominating membrane permeability under a given set of circumstances?
Nernst
which equation predicts the membrane potential at equilibrium when all permeant ion speices are taken into account?
Goldman-Hodgkin-Katz equation
the electrogenic Na+/K+ ATPase that maintains membrane potential moves what?
3Na+ out for every 2K+ moved in
just know: Ca-ATPase transports Ca2+ ions across the cell membrane