Definitions

Question 1

One coulomb is defined as

Answer 1

6.25 x 1018 electrons

Question 2

The charge of one electron (or univalent ion) is

Answer 2

1.6 x 10-19C

Question 3

Faraday’s constant

Answer 3

F = NAe0
= 6.022 x 1023 x 1.602 x 10-19
= 96,500 coulombs per mole

Question 4

Current

Answer 4

the net movement of positive charge per unit time. Unit = Ampere (A). One ampere of current represents the movement of 1 coulomb of charge per second.

Question 5

1 Ampere is defined as

Answer 5

the flow of 1 Coulomb of charge in 1 second

Question 6

Resistance is a measure of

Answer 6

The ease with which a charge moves through the conductor

Question 7

The reciprocal of resistance is

Answer 7

the conductance

Question 8

The unit of conductance is

Answer 8

siemen

Question 9

Capacitance indicates

Answer 9

how much charge can be stored for a given charging voltage

Question 10

Capacitance is measured in

Answer 10

farad (F): when 1 F is the capacitance of an element that can store 1 C of charge given a 1 V potential difference

Question 11

Factors affecting capacitance

Answer 11

Plate area, plate spacing and dielectric material

Question 12

How does capacitance relate to area?

Answer 12

C = (absolute permittivity of dielectric x area of plate overlap in square meters ) / distance between plates in meters

Question 13

P=

Answer 13

fraction of time the channel spends in the open state - can and normally dependent on voltage

Question 14

g=

Answer 14

single channel conductance

Question 15

i=

Answer 15

current that flows through a single channel when it opens

Question 16

Total current =

Answer 16

NiP

Question 17

3 factors of frequency coding

Answer 17

The strength-latency relationship and the

refractory period, together with the threshold

Question 18

Selective permeability arises from

Answer 18

selectivity of ion channels

Question 19

The equilibrium potential for an ion is the

Answer 19

potential difference that must be present across the

membrane of a cell in order to balance the concentration gradient for that ion.

Question 20

The Nernst equation states that the equilibrium potential of an ion is equal to

Answer 20

a constant (RT/Fz) times the natural logarithm of the ratio of the external to internal concentrations of the ion

Question 21

Why is the Nernst equation important?

Answer 21

equilibrium potential relative to the membrane potential determines the direction in which a given ion will flow through open ion channels.

Question 22

Potential Difference (V or E):

Answer 22

The potential difference between two points is the work needed to move a unit of positive charge (1 coulomb) frictionless from one point to
the other (= potential energy of the charge). Unit = Volt (V).

Question 23

To move a coulomb of charge across a 1-volt potential difference requires

Answer 23

a joule of work.

Question 24

Ra =

Answer 24

the internal longitudinal resistance of a 1 cm
length of a cylindrical process 1 cm2 in cross-sectional area. It is independent of geometry and it gives us a measure of how freely ions migrate through the
intracellular space.

Question 25

λ =

Answer 25

membrane length constant - sqrt ( rm/ra)

Question 26

Rm =

Answer 26

resistance of one square cm of membrane. Rm is independent of geometry, enabling us to compare the membrane of cells of different sizes and shapes

Question 27

Electrotonic conduction =

Answer 27

The passive spread of voltage changes along the neuron

Question 28

Electrotonic potential =

Answer 28

A non-actively propagated, local potential, resulting
from a local change in ionic conductance (e.g. synaptic or
sensory that engenders a local current). When it spreads along a stretch of membrane, it becomes exponentially smaller (decrement). Its spread and time course are largely determined by passive properties of the membrane.

Question 29

The threshold, VT, is the

Answer 29

specific value of Vm at which the net ionic current (INa + IK + Il) just changes from outward to inward, depositing positive charge on the inside of the membrane.