M&R - Membrane Potential Flashcards
How are membrane potentials expressed?
As potential inside the cell vs outside
What is membrane potential?
The electrical potential difference across the membrane.
What are membrane potentials measured in?
mV
How is resting potential established?
Selectively permeable membrane results in ion channels carrying ions across the membrane. This rapid flow of ions down their conc gradients results in resting potential.
What direction does sodium move across a membrane?
into the cell
What direction does potassium move across a membrane?
Out of the cell
What direction does chloride move across a membrane?
Into the cell
What direction does calcium move across a membrane?
Into the cell
Which ion movement dominates membrane potential in most cells?
Potassium
What happens when the chemical (diffusion) and the electrical gradient across the membrane is equal?
There is no NET movement of ions but a negative resting potential.
What is the Nernst equation?
This allows us to calculate the membrane potential at which K+ will be in equilibrium.
What is the potential for the Nernst equation of potassium?
-95mV
What is the real cell membrane like?
As well as potassium channels there are also sodium, calcium and chloride.
This alters membrane potential
How is overall membrane potential calculated?
Goldman- Hodgkin - Katz
What is depolarisation?
A decrease in the size of membrane potential.
Cell interior becomes less negative
What is hyperpolarization?
This is an increase in the size of membrane potential
Cell interior becomes more negative
How does depolarisation in resting cells occur?
Opening sodium or calcium channels
How does hyperpolarization occur?
This is by opening potassium or chloride channels
How do ACh receptors work?
These have an intrinsic ion channel which is opened by the binding of acetyl choline.
This allows sodium and calcium to move but not anions
Causes depolarisation
What are the 3 types of gating?
Ligand
Voltage
Mechanical
What is ligand gating?
Channel opens or closes in response to binding of a ligand
What is voltage gating?
Channels open or close in response to changes in membrane potential
What is mechanical gating?
Channels open/ close in response to membrane deformation
