resting potential Flashcards
what is a membrane potential and what is it caused by?
it is the static electric field developed by the separation of positive and negative charges across the cell membrane
what is depolarization?
a decrease in charge separation and a less negative membrane potential
what is hyperpolarization?
an increase in charge separation and more negative membrane potential
what is the capacitance?
the amount of electrical energy separated for a given electrical potential (C=Q/V)
what are the conductors and the dielectric in respect to membrane potential?
the conductors are the ECF and ICF and the dielectric is the membrane
how many K+ ions must be transferred inside the membrane to create the resting membrane potential?
very few (1/200,000 K+ into the cell) does not change the concentration in the bulk solution
what is the relative ion concentration inside and outside the cell for K, Na and Ca? Which plays the primary role in generating a resting potential?
K in>K out (generates resting potential)
Na in«Ca out
what is the direction of current flow?
the direction of net movement of positive charge
what type of transport generates resting potential? what other potentials do they create?
passive transport with selective gating channels
action, synaptic and receptor potentials
what is a diffusion potential?
the difference generated across a membrane when a charged solute diffuses down the concentration gradient
what is an equilibrium potential?
extension of diffusion principal
if there is a concentration difference for an ion across a membrane and the membrane is permeable, a potential difference occurs
what is electrochemical equilibrium?
when chemical and electrical driving forces are equal and opposite
if there are two concentrations of KCl across a membrane permeable only to K, what will happen? In what cells does this occur?
a membrane potential difference develops across the membrane (negative difference in the cell) and reaches equilibrium
occurs in glial cells
what is the Nernst equation and what does it calculate?
E=(RT/zF)ln([X2]/[X1])=(58/z)log([X2]/[X1])
calculates the potential across a membrane that is permeable to only one ion
what is the result of interstitial hyperkalemia and hypokalemia on the cell?
hyper-cellular depolarization
hypo- cellular hyperpolarization
what is a more realistic cell model of resting potential?
membrane has various ion channels that are permeable to K, Na and Cl
the membrane potential is not equal to the equilibrium potential to K
what equation is used to calculate the membrane potential with contributions from multiple ions? what does it include?
the goldman equation
it includes the permeability of each ion and its concentration on either side of the cell membrane
when does an ion have greater influence in determining the membrane potential?
when it has greater permeability across the membrane
what is alpha?
the permeability of sodium divided by the permeability of potassium (potassium is 25x more permeable)
what is different about Cl in the goldman equation?
the Cl inside is in the numerator instead of the denominator because it has a negative charge
in a squid giant axon, why is the theoretical Ek so different from the measured Vm (resting potential)?
because Ek does not take sodium ions into account (steady state potential instead of an equilibrium potential)
