Resting Membrane Potential Flashcards
Potential (E)
a voltage-separation of charge (in this case across the membrane) gives the ability to do work
Resting Membrane Potential
The difference between the inside and outside of a cell at rest (as steady state requires continual work and energy to maintain)
Depolarization
TOWARDS 0!
A change in the membrane potential
Is Resting membrane potential in equilibrium
no-steady state-it requires E
-50 –> -10V is?
Depolarization
+50 –> +10
Depolarization
Hyperpolarization
Away from 0
Current and units
Movement of charge (ions) in Amperes (A)
Resistance (R) and untis
Opposition to the flow of charge in Ohms
Ohm’s law
V=IR (Voltage=Current x Resistance)
Permeability
The ease with which a particular ION moves through an open channel
Conductance (g)
Opposite of resistance
-Defined as the ease of flow of CURRENT through an ion channel-the inverse of resistance
the inverse of resistance is
conductance
Na/K ATPase pumps what? Type of transporter
Primary transport-3 Na OUT and 2 K IN (per ATP)
Electrogenic
cell becomes more negative
(you lose one net charge by pumping 3+ out and just 2 +in
Two roles of the Na/K transported in the resting membrane potential
Indirect-most important-establishes ion gradient
Direct=electrogenic effect net flow of + out and - in
Most important role of Na/K pump
indirect-ion [c] –> gradient
What happens if you block Na/K pump
cell depolarizes from -70 to -55 or so
Indirect effect of Na/K pump
creates a Na and K gradient
electroneutrality
Cations and anions in each solution must exactly balance-if you had all one charge everywhere they would repel-thus the charge is associated with the membrane not in bulk solution
Generally more Cl- where and why?
Extracellular to balance - charge of organic ions-this might not always be the case
Where is the charge that creates membrane potential and why does it matter
Near the membrane-duh
Matters because you could not have lots of one charge floating around solution
Do you need to move a lot of ions in order to change the charge?
Nope
Electrical potential vs chemical potential
Electrical potential is a diff in charge (of all charge particles)
Chemical potential is a concentration outside vs the concentration on the inside (of a single ion type)
Equilibrium (reversal) potential
The membrane potential at which no net flux of an ion occurs-or in other words when an ion is allowed to move freely this is the potential that the ion will equilibrate at! -Called reversal b/c it is when the direction of ion through a channel is reversed
Which equation describes equilibrium potential
Nernst Equation
Know how to use and calc Nernst
..
R, T, F means
R=gas constant
T= temp
F=Faradays constant
Go - beyond equilibrium potential ion does what
moves in
Go + from eq. potential
ion moves out
Reversal potential for Na is about?
+60mV
Increasing Ion permeability does what
use K as ex
Increasing the membrane permeability of a particular ion will drive the membrane potential toward the equilibrium potential of that ion
K will drive membrane potential to -90
Which ion has the largest effect on resting membrane potential?
K
Sodium permeability at rest
LOW
If you let Na freely move
Brings membrane potential to +60V (depolarizing)
Electrogenic activity of the Na+/K+ ATPase adds how much charge?
~10 mV (direct effect)
