membrane potentials Flashcards
usual RMP (resting membrane potential)
-70 mV to -90 mV
types of excitable cells that transduce and transmit the impulse/electric event down the cell membrane
muscle, heart, nerve
what does RMP stand for
resting membrane potential inside the cell
what are the most important ions involved in cell membrane potentials?
sodium, chloride, potassium
what do you call an electrical potential across the cell where the electrical forces balance concentration forces?
nernst potential
what 3 things determine the nernst potential for a specific ion
concentration gradient
electrical gradient (electrical charge of the ion)
the electrolyte permeability across cell
the nernst potential for potassium is?
-94 mV
the nernst potential for sodium is ?
+ 61 mV
the nernst potential for calcium is?
+134
which is 100 times more permeable to the membrane and contributes more to the RMP Na+ or K+
K+
at rest, high ____ “leak” out of the cell
K+
who created the nerve action potential
alan hodgkins and andrew huxley
what initiates the opening of the Na+ channels?
strong stimulus
if the stimulus is strong enough, what might occur?
threshold will be reached
the threshold is reached and the voltage gated Na+ channels fly open (activation gate) in which stage?
depolarization
the membrane potential rises rapidly towards zero
the action potential now rises beyond the zero level and the interior of the cell becomes positive
in the overshoot stage “action potential”
which stage do the Na+ channels (inactivation gates) close and the voltage-gated K+ channels open?
repolarization
K+ rapidly diffuses out of the nerve cell and the interior of the cell becomes more negative
Na+ channels “inactivation gates” will not reopen until they are “reset” to the original RMP level
-In a depolarized state, Na+ channels will not reopen and muscle membrane cannot conduct action potential
ex: when using succinylcholine, muscle relaxants
in which stage does K+ move of out of the cell during the repolarization stage and passes the RMP moving toward the nernst potential?
hyperpolarization
hyperpolarization contributes to which period?
refractory period
what happens in the refractory period
the nerve/muscle is more difficult to stimulate because its hyperpolarized
during the hyperpolarization/refractory period is the cell more negative or positive?
more negative because it’s trying to reach its nernest potential while K+ channels are open
how much % of energy from brain fuels the Na+/K+ pump to carry out action potentials
70%
w/ each action potential, ___ leaves cell and ____ enters
K+, Na+
which stimuli invades the membrane and causes Na+ to diffuse inward through the nerve or muscle membrane and has the potential to set off an action potential?
mechanical disturbance, chemical effects, electrical stimulation
threshold is all or none
it’s either reached or not reached
what do you call it when the stimulus is not strong enough so an action potential is not generated?
local subthreshold potentials
which refractory period can still generate an action potential if the stimulus is stronger than normal?
relative refractory period
which refractory period cannot generate an action potential regardless of a strong stimulus
absolute refractory period
in the relative refractory period the cell is more negative than it usually is
local anesthetics- binds to and blocks the insides of Na+ channels making it difficult to open
low ECF K+ concentration- hyperpolarizes the membrane and RPM becomes more (-) = less excitability
High ECF Ca+ concentration
are all examples of what
membrane stabilizers
