The membrane potential at which the electrical gradient is matched by the concentration gradient. No net ion movement.
1 of 14
What is the formula for the Nernst Equation?
Ea = 58/z x log([A]o/[A]i)
2 of 14
Why is the resting membrane potential slightly positive to Ek?
The membrane is not entirely selective for K only.
3 of 14
What determines the membrane potential?
The permeability of the membrane to ions. The membrane potential moves twoards the equilibrium potential of the dominant ion at the time.
4 of 14
Why are there permeability changes during an action potential?
Due to volatge sensitive ion channels opening and closing.
5 of 14
What causes the rising phase of the action potential?
Sodium ions entering through sodium channels. The AP peaks at ENa.
6 of 14
What are the roles of Na and K ions during the action potential?
Na ions depolarise and K ions repolarise the membrane.
7 of 14
Describe the positive feedback mechanism of the AP upstroke.
Na channels open due to depolarisation leading to Na influx and further depolarisation. This positive feedback mechanism makes it very fast.
8 of 14
Describe the negative feedback mechanism of AP repolarisation.
Depolarisation causes K channels to open leading to K efflux carrying positive charge out of the cell causing repolarisation. This process is much slower than the AP upstroke.
9 of 14
What is the voltage clamp technique?
A way of controlling membrane potential and measuring the movement of charged ions across the membrane as electric current.
10 of 14
What are the main features of the voltage clamp technique?
A feedback amplifier supplies current to rapidly return membrane potential to a certain level (the command potential). The supplied curren compensates for (and is therefore a measure of) membrane currents.
11 of 14
What are the main methods for removing Na current?
Pharmacological agents e.g. tetrodotoxin, replacement with a non permeable ion or changing ENa to 0 so there is no net movement of sodium.
12 of 14
What is the formula for the conductance of sodium?
GNa = INa / (Vm-ENa)
13 of 14
What shapes the AP?
Alterations in the conductance of the membrane to ions with time.
14 of 14
Other cards in this set
Card 2
Front
What is the formula for the Nernst Equation?
Back
Ea = 58/z x log([A]o/[A]i)
Card 3
Front
Why is the resting membrane potential slightly positive to Ek?
Back
Card 4
Front
What determines the membrane potential?
Back
Card 5
Front
Why are there permeability changes during an action potential?
Comments
No comments have yet been made