Definitions Flashcards

1
Q

One coulomb is defined as

A

6.25 x 1018 electrons

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2
Q

The charge of one electron (or univalent ion) is

A

1.6 x 10-19C

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3
Q

Faraday’s constant

A

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

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4
Q

Current

A

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.

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5
Q

1 Ampere is defined as

A

the flow of 1 Coulomb of charge in 1 second

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6
Q

Resistance is a measure of

A

The ease with which a charge moves through the conductor

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7
Q

The reciprocal of resistance is

A

the conductance

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8
Q

The unit of conductance is

A

siemen

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9
Q

Capacitance indicates

A

how much charge can be stored for a given charging voltage

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10
Q

Capacitance is measured in

A

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

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11
Q

Factors affecting capacitance

A

Plate area, plate spacing and dielectric material

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12
Q

How does capacitance relate to area?

A

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

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13
Q

P=

A

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

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14
Q

g=

A

single channel conductance

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15
Q

i=

A

current that flows through a single channel when it opens

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16
Q

Total current =

17
Q

3 factors of frequency coding

A

The strength-latency relationship and the

refractory period, together with the threshold

18
Q

Selective permeability arises from

A

selectivity of ion channels

19
Q

The equilibrium potential for an ion is the

A

potential difference that must be present across the

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

20
Q

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

A

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

21
Q

Why is the Nernst equation important?

A

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

22
Q

Potential Difference (V or E):

A
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).
23
Q

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

A

a joule of work.

24
Q

Ra =

A

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.

25
λ =
membrane length constant - sqrt ( rm/ra)
26
Rm =
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
27
Electrotonic conduction =
The passive spread of voltage changes along the neuron
28
Electrotonic potential =
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.
29
The threshold, VT, is the
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.