Lecture #4: Resting Potential Flashcards
What ions does the extracellular fluid primarily contain?
Na+
Cl-
What ions does the cytoplasm primarily contain?
K+
Cl-
What does the Na/K ATPase do?
pump 3 Na+ out
2 K+ in
How is the resting potential generated? Is it active or passive?
movement of ion through ion channels, down their concentration gradients
passive
What two conditions are present at the equilibrium potential?
- chemical force (concentration difference) = electrical driving force (net flux = 0)
- Ionic movement of K+ from 1 to 2 = Ionic movement of K+ from 2 to 1
What equation is used to find the resting potential?
Nernst
Ex = (RT/zF)ln([X2]/[X1]) = (58/z)log([X2]/[X1])
What does interstitial hyperkalemia lead to? What does interstitial hypokalemia lead to?
Hyperkalemia –> cellular depolarization
Hypokalemia –> cellular hyperpolarization
The membrane potential is proportional to the _____
ion gradient
What is the slope of a graph of membrane potential versus the log of the concnetration gradient?
50mV/decade change in concentration gradient
What does increasing [K+]o cause?
depolarization of the membrane
larger gradients lead to _____ of the membrane
larger polarization
________ to K+ is cause by K+ permeable membrane channels which are open in _____ and stay open _____
- Selective permeability
- Resting neurons
- All the time
There is more K+ _____ the neuron than ____ because of the Na/K Pump
inside
outside
The resting potential across the membrane represents an _______ between the concentration gradient of ___ and an opposing electrical gradient
- Electrochemical equilibrium
- K+
The resting potential to a cell only permeable to K+ is an _____ and can be calculated with the _____
- equilibrium potential
- Nernst equation
The basic mehcnaism underlying resting membrane potential can be understood in an “ideal cell” in which a membrane ______ to K+ divides solutions with _____ of K+
- only permeable
- different concentrations
To find a more realistic resting potential of a cell permeable to both K+ and Na+, what equation is used?
Goldman equation
What two things does the Goldman equation take into account?
- concentration of ion
- permeability of membrane for ions
The rate of change of membrane potential is set by the membrane ______
capacitance
The magnitude of the change in membrane potential is set by the membrane ______
conductance
In a realistic cell, the membrane potential is a _____ - not an equilibrium potential
steady state potential
