Resting Potential Flashcards
In terms of elective voltage across the cell membrane what effect does reducing the charge separation have?
It makes the membrane potential less negative. It has a depolarizing effect.
In terms of elective voltage across the cell membrane what effect does increasing the charge separation have?
It makes the membrane potential more negative. It has a hyper polarizing effect.
What are the two major players in the generation of membrane potentials?
1 - Ion pumps. They are active transporters that establish ionic gradients.
2 - Ion channels. They allow the movement ions in order to reach an electrochemical equilibrium.
Describe the 4 major ions that play a role in membrane potential and where their concentrations are highest.
K is highest in the cell. Cl- is highest in the cell. Na+ is highest outside the cell. Ca++ is highest outside the cell. K+ is the primary ion is generation of the resting potential, however Na+ plays a small role too. Cl- may play a role (not in this lecture)
How does the Na/K ATPase pump ions?
Through the use of ATP hydrolysis to drive 3 Na+ out and 2 K+ in.
How is the direction of current flow defined?
As the direction of net movement of positive charge.
What is a diffusion potential?
It is the potential difference generated across a membrane when a charged solute diffuses down its concentration gradient. Equilibrium potential is an extension of this.
If for instance you had a membrane selective to Na+ between two solutions of NaCl and on one side you had a 1M solution and the other side had a .1M solution describe what would happen to Na+ ions and what would happen to the concentration on the bulk side.
Na+ would diffuse down its chemical gradient across the membrane until its electrochemical equilibrium was met. This would not produce any change in the Na+ concentration in the bulk solution.
What is the Nernst equation? When can it be used?
Ek = RT/zF ln [X1]/[X2}. It can be used to calculate the resting potential of membranes selectively permeable to only 1 ion. R is the fast constant. F is faradays constant. T is absolute temperature in degrees K. Z is valence of permeable ion. Glial cells only have K+ channels.
Interstitial hyperkalemia causes _______.
Interstitial hypokalemia causes ________.
Hyperkalemia - depolarization
Hypokalemia - hyperpolarization
The Goldman equation allows one to calculate what? What is the formula?
It accounts well for the contributions of K+ and Na+ ions to the resting potential.
Vm = -58 long ([K+]o + a [Na+]o / [K+]i + a [Na+]i) where a = Pna/Pk and P is the permeability
When Vm is determined by two or more species of ions the influence of each is determined by..
their concentration gradients and by the permeability of each ion crossing the membrane.
What effect does a greater permeability have on the steady state resting membrane compared to the equilibrium potential of that ion?
The greater the permeability the closer the steady state resting membrane will be to the equilibrium potential of that ion.
How does the permeability of K compare to that of Na?
It is 25 times more permeable than Na
At resting potential the ratio of Pk: Pna: Pcl is 1.0: .04: .45. What is it at the peak of the action potential?
1.0 : 20 : .45. This implies that the permeability of Na changes greatly while that for K and Cl does not change.
