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

1

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

### insulator

2

## two conductors separated by an insulator form an _______ _______

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

3

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

### farads (F), coulombs per volts

4

## what gives the membrane its electrical conductance

### channel proteins that allow ions to pass

5

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

### resistance (R), conductance (g)

6

## what is the resistance of a membrane

###
measure of its impermeability to ions

equal to the inverse of conductance R=1/g

7

## 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

8

## 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

9

## 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

10

## input resistance

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

11

## 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

12

## capacitative current

###
ions interacting across a membrane

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

13

## dielectric constant

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

14

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

###
its thickness

dielectric constant

15

## the capacitance of a membrane affects...

### how it responds to change in applied voltage or current

16

## 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

17

## ohms times coulombs yields...

### units of seconds

18