L2 - Bioelectricity Flashcards Preview

BMS242 Core Phys Pharm > L2 - Bioelectricity > Flashcards

Flashcards in L2 - Bioelectricity Deck (24)
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1

How can Vm be measured

Similar method to a patch clamp
But electrode straight through the membrane

2

EC Na conc

150 mM

3

IC Na conc

15 mM

4

EC K conc

5 mM

5

IC K conc

150 mM

6

EC A- conc (anion)

0

7

IC A- conc

65 mM

8

How are all of these Na and K concentrations maintained

Na/K ATPase

9

Two blockers of the Na/K ATPase

Digoxin
Ouabain

10

When Na/K ATPase blocked what is the effect on Vm

Vm --> o mV

11

Why is the Na/K ATPase electrogenic

Net loss of one +ve charge

12

Contribution of K channels to the equilibrium potential

CONCENTRATION
Tends for K to move out, down gdt
POTENTIAL
Tends for K to move in, down gdt

Equilibrium potential
Two gradients equal no current flow

13

Nernst equation

(61.2/z) x log [x]i / [x]o

14

Nenst equation for K

61.2 x log (5/150)

= -90.1 mV

15

Contribution of Na channels to the equilibrium potential

CONCENTRATION
Tends for Na to move in, down gdt
POTENTIAL
Tends for Na to move out, down gdt

Equilibrium potential
Two gradients equal no current flow

16

Nernst for Na

61.2 x log (150/15)

= +61 mV

17

Goldman equation

Vm = (61.2/z) = log (pna[Na]o + pk[k]o) / (pna[Na]i + pk[k]i)

18

What does goldman equation determine

Membrane potential

19

Approximate Vm

-70 mV

20

Three movements of ions at Vm

Na (Ena)
K (Ek)
Na/K ATPase

21

If there is a change in Vm then what else must there be a change in

Change in the permeability to electrogenic transport

22

Describe the ion channels and movement of ions at a resting Vm

Many K channels are open
Many Na channels are closed
Vm --> Ek

23

What happens when threshold is reached

Voltage gated sodium channels open and the membrane potential approaches Na Nernst

24

Describe the significance of Na - Amino acid transport

Couple down hill transport of the Na gradient to the influx of amino acids
Cell is able to sustain a high level of Na transport whilst keeping the Vm close to resting
This is done by the opening of K channels in the membrane