MCP 26: Introduction to Neurophysiology-Membrane Potentials Flashcards
electrical properties of an ion channel
1.) amount of current that can flow is dependent on voltage and conductance 2.) mean open time 3.) how often do they open 4.) selectivity of the channel for specific ions
resting membrane potential (RMP)
due to leak channels selective for Na+ and K+ and impermeable intracellular anions
conductance
G=1/R; has units of Siemens; how much current will flow through a resistance than not; I=GV (re-written form of Ohm’s law); increasing number of ion channels in parallel circuit, decreases R, which increases G
capacitance
ability to store change; C=q/V; measured in Farads; capacitance decrease with distance between the plates and increases with their size, in cell model, the lipid bilayers are the insulator part of the capacitor and the fluid layers are the platesj
order of magnitude for body’s electrical measurements
mV, pA, Mohms, nS, pF
ohm’s law
V=IR
Nernst equilibrium
AKA electrochemical equilibrium; flow of ions out due to concentration gradient is equaled by the electrical gradient pulling them back in
Nernst equation for equilibrium potential
Ek=RT/ZF 2.3logKo/Ki, can be simplified to Vm=60/Z log Ko/Ki where the temperature=30 degrees C
conductance
electrical property due to current of ions
permeability
number of ion channels in a membrane; membrane will still have permeability by no conductance if ions are not present
steady state
IK+INA=0, depends on ion concentrations and relative number of Na+ and K+ channels
typical cell resting potential
-70 to -90 mV
oubain
potent inhibitor of Na+/K+ ATPase
hyperpolarize
make more negative
GHK equation
determines resting membrane potential using multiple ions, assume sum of all currents is equal, not easy to measure permeability; equation rarely used
