Module 4 - Intro to Resting Membrane Potential Flashcards
What are the three types of potentials to consider?
Resting membrane potential
Action potential
Graded potential
What is RMP?
The membrane voltage when the neuron/cell is at rest.
What are action and graded potentials?
Are fluctuations from RMP caused by the opening of ion channels.
What does excitation equate to?
Depolarization from RMP
What does inhibition equate to?
Hyperpolarization from RMP
What types of cells have more polarized RMPs? What is their RMP range?
Neurons, muscle and glial
-30 to -90 mV
What types of cells have less polarized RMPs? Give examples and state their range.
Non-excitable cells
e.g., epithelial, RBCs
-8 to -30 mV
What three things do ion pumps and exchangers ensure in all living cells (including bacteria)?
K+ is more abundant inside than outside
Na+ is more abundant outside than inside
Ca2+ is very low inside
What ion concentration gradient can vary during development?
Cl-
Why must Ca2+ be very low inside the cell
Toxic: precipitates proteins and organic/inorganic ions
How do sea water animals differ in terms of ion concentrations compared to mammals?
Have more than double the ion concentrations compared to mammals
How are mammals and sea water animals similar in terms of ions?
Roughly the same ratios across the membrane, K+ more abundant inside and Na+ more abundant outside.
What type of energy acts on ions in a cell?
Electrical potential energy (voltage)
Random kinetic energy
What does the total energy for moving a given ion through an aqueous cellular environment come from?
Voltage (Vm)
Concentration gradient of that ion.
What determines the direction of an ion’s flow?
The balance between its gradient and the membrane voltage.
What does the Nernst equation calculate?
The membrane voltage for a given ion concentration gradient where movement of ions stops (i.e., equilibrium potential).
What is the equilibrium potential?
A voltage that exactly opposes the diffusion energy of an ion gradient.
Give the Nernst equation and define the variables.
Eion = RT/zF ln([ion]out/[ion]in)
R - gas constant
T - absolute temperature in K
z - valence of the ion
F - faraday constant