Lecture 4

Question 1

Bioelectricity

Answer 1

Membrane potential

Question 2

Measurement of Vm

Answer 2

Measured in a similar way to patch-clamp
Reference electrode used
measures different between the reference electrode and one in the cell
Sharp electrode and smaller than PC method

Question 3

Determination of Vm

Answer 3

Unequal distribution and the selective movement of a few ions

Question 4

Na+ extracellular concentration

Answer 4

150mM

Question 5

Na+ intracellular concentration

Answer 5

15mM

Question 6

K+ extracellular concentration

Answer 6

5mM

Question 7

K+ intracellular concentration

Answer 7

150mM

Question 8

A- intracellular concentration

Answer 8

65mM

Question 9

A- extracellular concentration

Answer 9

0mM

Question 10

Na+/K+ ATPase

Answer 10

Maintains ion distribution
3 Na out and 2 K out
Direct contribution to the Vm of 20%
Electrogenic - causes loss of one +ve charge
indirectly controls intracellular Na+ and K+ levels

Question 11

K+ channel contribution

Answer 11

K+ exits cell to leave negative charge
Negative charge attracts K+ into the cell from ECF
Eventually reaches equilibrium - no net movement of ions = no current

Question 12

Nernst Equation

Answer 12

Eion=RT/zF x Ln[ion]out/[ion]in

Question 13

Nernst Eion

Answer 13

Equilibrium potential

Question 14

Nernst R

Answer 14

Gas constant

Question 15

Nernst T

Answer 15

Temperature in Kelvin

Question 16

Nernst Z

Answer 16

Valance ion
(Ion charge)

Question 17

Nernst F

Answer 17

Faradays constant

Question 18

Nernst for K+ channels

Answer 18

Workout out for passive K+ only = -90mV
Cell membrane = -70mV
Proves there must be other ions moving across the cell

Question 19

Na+ channel contribution

Answer 19

Na+ moving into the cell
Positive charge and membrane potential produced
Positive charge repels more Na+ from entering
Low amount of Na+ enters

Question 20

K+/Na+ channels ratio

Answer 20

Less Na+ entering than K+ leaving (Nernst)
More K+ than Na+ channels open
Ratio determined by membrane permeability

Question 21

Na+ restive permeabilities

Answer 21

1

Question 22

K+ relative permeabilities

Answer 22

50-74

Question 23

A- relative permeability

Answer 23

0

Question 24

The Goldman Equation

Answer 24

Vm= RT/zF ln P[Na]o + P[K]o/ P[Na]i + P[K]i

Question 25

Vm value

Answer 25

-78 – -81mV

Question 26

Movement at Vm

Answer 26

Passive movement of Na+ into and K+ out of the cell

Active Na+/K+ ATPase moves 2Kl and 3NO

Question 27

Change in Vm =

Answer 27

Change in permeability to electrogenic transport

Question 28

Voltage-gated Na+

Answer 28

Resting - many K+ channels open and many Na+ closed so Vm–> EK
When threshold is reached there is opening of the VGNC and Vm –> ENa

Question 29

Na+/Amino Acid Co-transport

Answer 29

Epithelial cell
Binds Na+ and aa and transports both into the cell using the Na+ gradient
Stimulating Na+ proteins causes depolarisation
Able to keep high level of Na+ transport whilst keeping Vm close to resting via opening K+ channels in the membrane