Electrical properties Flashcards
L7 L10
How are electrical events measured?
Intracellularly, extracellularly and via patch clamping
At rest, where is the -ve side of the membrane?
Intracellularly
What is the shape of the action potential graph intracellularly?
Extracellularly?
https://o.quizlet.com/nt54nwjOFUD6Yb30lv33Ow_b.jpg%252F%26psig%3DAOvVaw1Iwf4-gofTtvS-8L3J0qnK%26ust%3D1574715661082372&psig=AOvVaw1Iwf4-gofTtvS-8L3J0qnK&ust=1574715661082372
Intracellular peak to trough is around 100mV
Extracellular is the exact same, but just on a smaller scale (0.1mV)
What is capacitance?
Membranes ability to store ionic charges on its inner and outer surface
How does the membrane allow electrochemical gradient to be established?
The electrochemical gradient is established because of the Na+/K+ ATPase pump and the membrane channel allowing restricted movement of ions.
Nernst equation
E= (RT)/(zF) x Log([C]out / [C}in)
(RT)/(zF) is usually 58 mV so
E= 58 x Log([C]out / [C]in)
What is the equilibrium potential for an ion?
The voltage the membrane needs to be at to prevent the ion to not be able to diffuse across the membrane.
What is the equilibrium potential for K+ and Na+? (specific values)
=-90mV for K+
=+60mV for Na+
What is the resting membrane potential?
Around -70mV
What happens to the Vm if the membrane becomes permeable to a specific ion?
The ion will diffuse down its concentration gradient and move the Vm towards the ions equilibrium potential.
1) What is the driving force for the K+ ion?
2) What is the driving force for the Na+ ion?
3) Why is there no diffusion of ions despite the different driving forces?
Driving force = membrane potential - equilibrium constant for the ion
1: -70mV - -90mV = +20mV drivng force for K+
2: -70mV - +50 mV = -120mv driving force for Na+
3: The membrane is about 50x more permeable to K+ ions than Na+ ions
What is the conductance?
The amount of charge that actually moves across the membrane.
What are the 3 stages for an action potential to occur?
Depolarisation, Hyperpolarisation
Restoring resting membrane potential
According to lecture notes: depolarisation, repolarisation and hyperpolarisation
What do Schwann cells do in terms of action potentials?
Schwann cells are insulating material. They allow local circuits to only occur in the Node of Ranvier, which greatly increases the speed of conduction due to saltatory conduction (activation at a distance).
What is the concentration gradient described as for +ve and -ve ions?
+ve: [C]out/[C]in
-ve: [C[in/[C]out
What is the Hodgkins Katz equation?
Vm = 58 x Log[(Pk[K+]out + PNa[Na+]out)/(Pk[K+]in + PNa[Na+]in)]
Pk = relative permeability of K+ PNa = relative permeability of Na+
