Membrane Potentials Flashcards
What is the Membrane Potential?
An electrical potential (potential difference) that exists across the plasma membrane.
This is a result of membrane semi-permeability.
What is the principle of macroscopic
electroneutrality?
Body fluids are electrically neutral.
That is, each compartment must have the same concentration, in mEq/L.
+Charge = -Charge.
What are the charged solutes in body fluids?
-In ECF, Sodium is the major cation (Slightly more), and chloride and bicarbonate are the major anions.
-In ICF, Potassium and magnesium are the major cations, and proteins and nucleotides are the major anions (Slightly more).
What is Membrane Potential?
(Another definition)
The difference in charge distribution near the plasma membrane
What is the Electrochemical Potential Gradient?
The combined chemical driving force (chemical potential) and electrical driving force (electrical potential) that determines net ion movement. It is also called the electrochemical driving force.
Chemical potential + Electrical Potential.
What is the Equilibrium Potential?
Electrical & Chemical driving forces are equal & in opposite directions. The net direction of movement is zero.
Net ion movement is such that it will bring the membrane potential closer to the ion’s equilibrium potential.
Ions in the ICF:
proteins, amino acids, and nucleotides.
Magnitude of membrane potential:
The size of the charge difference.
What does the membrane potential reference?
The ICF.
What charge is the ICF?
What charge is the ECF:
ICF: Negative
ECF: Positive.
What unit is the membrane potential expressed in?
Millivolts.
What type of cells can produce a membrane potential?
Excitable cells such as neurons and muscle cells.
Action potential:
Large rapid changes in membrane potential in response to a stimulus.
Membrane potentials are important for?
Production of Action potential
Filtration of solutes.
Resting Potential:
-70 millivolt.
