05_Membrane Potential Flashcards
What is an example of an electrogenic pump?
Na+/K+ ATPase
The inside of the plasma membrane is (negative/positive) compared to the outside.
negative
What is membrane potential?
The difference in electric charge across the plasma membrane (aka voltage gradient)
What is the equilibrium potential for an ion? What equation is used to calculate it?
Membrane potential at which equilibrium is reached (no net flow of ion thru channel).
The Nernst equation.
What is the membrane potential of most non-excitable cells?
-70mV
What is the membrane potential of an excitable cell termed?
resting potential
What are the three main classes of ion channels? (_____-gated)
1) Voltage-gated
2) Ligand-gated
3) Stretch/Pressure (Mechano-) gated
What do voltage-gated ion channels open/close in response to?
depolarization of the membrane
Which class of ion channels open upon binding a chemical messenger?
Ligand-gated channels
What do mechano-gated ion channels open in response to?
stretching or deformation of cell surface
Why type of ion channel does Ach bind to? What is this receptor called? Which ion can be transported?
Ach binds to an extracellular ligand-gated ion channel called nAchR.
Binding of Ach opens the channel and allows Na+ influx into the cell.
Describe an example of a channel that responds to stretch/pressure.
Cation channels open in response to movement of stereocilia in the ear (due to sound)
What ensures that the action potential is only propagated in one direction?
Refractory period, in which ion channels are inactive (and do not respond to stimulus).
What is the lipid:protein composition of myelin?
80: 20
lipid: protein
Where are voltage-gated Na+ channels in the axon concentratted?
Nodes of Ranvier
