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.
Factors that increase speed of conduction.
Thicker diameter (less resistance) Myelinated (allows saltatory conduction)
