Electrical Properties of Cells Flashcards
What is the extracellular concentration of Na+?
140mmol/litre
What is the intracellular concentration of Na+?
10mmol/litre
What is the extracellular concentration of K+?
4mmol/litre
What is the intracellular concentration of K+?
120mmol/litre
How is an electrochemical gradient established?
Na+/K+ ATPase pump.
Pumps 3Na+ out for every 2K+ in.
Overall causes the inside cell to become negatively charged compared to the outside.
What is the equilibrium potential?
When there is no net movement of the ion.
Force pushing K+ out (concentration gradient) = electrical force pulling K+ in (electrical gradient)
What is the Nernst equation?
E.z.F = R.T. ln([Cout]/[Cin])
Used to calculate cell potentials.
What is the equilibrium potential for K+ at physiological concentration?
Ek = -90mV
What is the equilibrium potential for Na+ at physiological concentration?
ENa = +50mV
What is the resting membrane potential of a cell?
around -70mV
Why is the membrane potential closer to the equilibrium potential of K+ than Na+?
Because the cell membrane is 50 times more permeable to K+ than it is to Na+
Name the 4 phases of an action potential.
Depolarisation
Repolarisation
Hyperpolarisation
Refractory period
What happens to the Vm(membrane potential) when a cell becomes permeable to an ion?
The Vm with move towards the Eeq of the ion.
Describe how depolarisation occurs.
Stimulus opens some Na+ channels. Na+ ions enter cell. Trigger voltage-gated ion channels to open. Influx of Na+ causes depolarisation.
How does the action potential propagate down the axon?
Localised currents cause depolarisation further along the membrane.
