Origin of membrane potentials Flashcards
Revision
In what way are the plasma membranes of all cells polarised?
The plasma membranes of all cells are polarised electrically.
What is the definition of membrane potential?
Membrane potential (Em (m is a subunit)): separation of opposite charges across the membrane.
What are the units of membrane potential?
mV (1/1000 volt)
What is the process for membrane potential?
Membrane has no potential when the charges on either side are equal.
Membrane has potential when the charges on either side are unequal.
The membrane separates the charges and on either side is the remainder of fluid electrically fluid. Separates charges responsible for potential.
Magnitude of potential: membrane B has more potential than membrane A and less potential than membrane C.
Separated charges form a layer along the plasma membrane.
Is the membrane itself charged?
NO
What does Em (m is subscript) refer to?
Em refers to the difference in charge between the thin layers of ECF and ICF located next to the inside and outside of the membrane, respectively.
What is EM due to?
differences in the concentration and permeability of key ions.
What cells have membrane potential?
All cells have membrane potential.
What do excitable cells (nerve and muscle) have the ability to do?
They have the ability to produce rapid, transient changes in their membrane potential when excited (action potentials).
What is the resting membrane potential?
Resting membrane potential is the constant in non-excitable cells, and in excitable cells at rest.
What is responsible for the electrical properties of the membrane?
Unequal distribution and their selective movement through the plasma membrane are responsible for the electrical properties of the membrane.
What ion concentration is always greater extracellularly than intracellularly?
The sodium ion concentration is always greater extracellularly than intracellularly.
Although the values will vary between cell type (and species), what are the estimated concentrations of sodium and potassium ions inside and outside the cell?
The sodium ion concentration (millimoles/litre; mM) extracellularly is 150 and intracellularly is 15 with a relative permeability of 1.
The potassium ion concentration (mllimoles/litre; mM) extracellularly is 5 and intracellularly is 150 giving a relative permeability of 100 (for a skeletal cell).
What are the concentration gradients for K+ and Na+?
The concentration gradient
- for K+ is outward
- for Na+ is inward
As K+ and Na+ are cations, the electrical gradient for both will always be toward what?
As K+ and Na+ are cations, the electrical gradient for both will always be towards the negatively charged side of the membrane.