Resting Membrane Potentials Flashcards
Which cells have a resting membrane potential?
All cells
Which cells are excitable?
Muscles and neurones
What is the resting potential of a nerve cell?
-70 mV
How does a resting membrane potential arise?
Due to separation of charges across a membrane due to different numbers of cations and anions in intracellular and extracellular fluid.
How is an equilibrium of potassium ions maintained in a cell?
Potassium ions naturally move down the concentration gradient from inside to outside the cell. As this occurs, the cell becomes less negative, so an electrical gradient is set up in the reverse direction to attract potassium back into the cell.
Which ion most influences resting membrane potential?
Potassium.
How does the Na+/K+ ATPase pump work?
Maintains the RMP - pumps out 3Na+ for every 2K+ into the cell.
How does hyperkalaemia alter the RMP?
More K+ outside of the cell, so less K+ diffuses out of the cell and this cell becomes more depolarised. The cell is more excitable.
What happens to the RMP with hypokalaemia?
Reduced extracellular K+ so greater K+ diffusion out of the cell, causing a less negative RMP and so less excitable cell.
What does depolarisation mean?
Potential inside the cell becomes more positive
What does polarisation mean?
Membrane has potential, there is a separation of charge
What does repolarisation mean?
Membrane returns to RMP
What does hyperpolarisation mean?
Potential becomes more negative inside the cell, more charges separated than at RMP
What is the threshold?
The membrane potential at which an action potential will occur.
