Exam 2: Ch 5 Book Electrical Properties & Equations Flashcards Preview

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Flashcards in Exam 2: Ch 5 Book Electrical Properties & Equations Deck (18):

the plasma membrane is impermeable to ions and therefore is an _______



two conductors separated by an insulator form an _______ _______

electrical capacitor: a device that can store energy in the form of separated electric charges


amount of electrical charge stored on the two sides of a capacitor is measured in units of...

farads (F), coulombs per volts


what gives the membrane its electrical conductance

channel proteins that allow ions to pass


electrical ______ and electrical _____ both characterize how readily charges can move in a circuit

resistance (R), conductance (g)


what is the resistance of a membrane

measure of its impermeability to ions

equal to the inverse of conductance R=1/g


for a given transmembrane voltage, the lower the resistance...

the higher the conductance

the more ionic charges will cross the membrane through open ion channels per unit time


Ohm's law

the voltage drop produced across a membrane by a current that passes through it is directly proportional to current times resistance of the membrane

ΔVm = ΔI x R

shows relationship between current, resistance, and steady-state voltage


units of Ohm's law

ΔVm (volts) = the voltage drop across the membrane

ΔI (amps) = current across the membrane

R (ohms) = electrical resistance of the membrane


input resistance

total resistance encountered by current flowing in or out of the cell


what does input resistance depend on

surface area of cell memb. (A) b/c membrane of a larger cell has more ion channels

density of channels per unit area


capacitative current

ions interacting across a membrane

when voltage applied, ions build up on either side and interact


dielectric constant

property that reflects the inherent ability of an insulator to store charge


amount of charge separated by a layer of insulation depends on...

its thickness

dielectric constant


the capacitance of a membrane affects...

how it responds to change in applied voltage or current


equation between potential and time during the charging of the capacitance

Vsubt = Vsubinfinity(1 - e^(-t/RC))

Vsubinfinity = potential across capacitor at time t = infinity

t = time in secs after onset of current pulse

R = resistance of circuit in ohms

C = capacitance of the circuit in farads

Vsub t = potential capacitor at any time t


ohms times coulombs yields...

units of seconds


together, _______ and _______ give the membrane a time-dependent response to changes in voltage; the time course of the response depends on the sizes of the resistance and the capacitance

resistance, capicatance