RMP & Excitability Flashcards
Define resting membrane potential
difference in electrical potential across cell membrane
because membrane potentials are expressed relative to extracellular fluid, when membrane potential is negative it means
inside of cell more negative than outside of cell
what is responsible for the majority of the resting membrane potential
K+ and Na+ flowing through leak (non-gated) channels
how much does the sodium potassium pump contribute to RMP
-4mV
how does the sodium potassium pump contribute -4mV to RMP
net positive charge outside of cell, 3 sodium out for every two potassium in
what is the purpose of the goldman-hodgkin-katz equation?
the influence of K+, Na+, and Cl- on the membrane potential
what does P stand for in goldman equation
permeability of the membrane
what does o and i stand for in goldman equation
i is inside the membrane
o is outside the membrane
write out the goldman-hodgkin-katz equation
pg 6
if one ion’s permeability becomes greater than anothers, what happens
for that ion the membrane potential approaches equilibrium
usually, how much greater is permeability for potassuim than sodium
20-25
why doesn’t chlorine ions contribute significantly to resting membrane potential?
resting membrane potential for the cell is almost identical to equilibrium potential for chlorine
a 10 fold concentration change in extracellular K+ will change RMP by what
60 mV
why wouldn’t a 10 fold concentration in extracellular Na+ change RMP by 60 mV?
permeability of Na to K is MUCH smaller (1:20-25)
so it would have little to no affect on membrane potential
what is conductance
the ability of a given ion species to carry electrical current across the membrane
what does conductance depend on
permeability and concentration
what is purpose of ohm’s law
can predict amplitude of ion fluxes
what relationships does ohm’s law specify
current, electromotive force, conductance
what is current
flux of charge carriers
what is electromotive force
force that drives the fluxes
write out ohm’s law
V = IR
state what variables stand for in Ohm’s law
V = voltage I = electrical current R = resistance
if there is high resistance, what happens to conductance
low conductance
if there is low resistance, what happens to conductance
high conductance
what does gion stand for
conductance
Iion stands for?
electrical current carried by ion
Iion =? (give equation)
Iion = gion (Vm - Eion)
Vm stands for
membrane potential
what is depolarization
membrane potential is less negative than resting potential (more positive)
what is hyperpolarization
membrane potential is more negative than resting potential
at resting potential what are voltage gated channels doing
they are closed
leak channels for potassium and sodium generate
resting membrane potential
are channels besides leak involved in generating resting membrane potential
no
more positive is
depolarization
more negative is
hyperpolarization
resting potential of a myelinated neuron fiber is primarily dependent on concentration of which ion?
K+
To calculate conductance what equation do you have to use
Ohm’as law
V=IR
magnitude of current when you’re not at equilibrium potential for ion, use
ohm’s law
when you’re at equilibrium potential what is current
0
voltage clamp to -89 the cell what does it mean
make -89 relative to outside the cell
anything below x axis is
inward current, negative number
anything above x axis is
outward current, positive number
Vm is where on a x y graph
x axis
I (current) is where on a x y graph
y axis
what happens excitability in depolarization
more excitability
what happens to excitability in hyperpolarization
less excitability
