Resting Membrane Potential Flashcards
What 2 functions do proteins in the neuronal membrane perform to establish and maintain the resting membrane potential?
Channels & transporters. channels allow the selective movement of ions across the membrane along the concentration gradient. Transporters actively transport ions across the membrane against the concentration gradient.
On which side of the neuronal membrane are Na+ ions more abundant?
Extracellular
What is the Na+/K+ ATPase?
Na/K Adenosine TriPhosphatase is the active transport protein, it uses ATP to move 3 sodium out of the cell and 2 potassium into the cell.
Why is the Na+/K+ ATPase important?
establishing & maintaining an electrical potential across the membrane
How is the Na+/K+ ATPase regulated?
by the ionic concentration gradient and the electrical potential across the membrane
When the membrane potential is equal to the potassium equilibrium potential, in which direction (in or out) is there a net movement of potassium ions?
There is no net movement of ions - the rate of diffusion out of the cell is the same as the movement due to the electrical field.
There is a greater K+ concentration inside the cell than outside. Why then is the resting membrane potential negative?
Because the membrane is selectively permeable and contains potassium leak channels that allow K+ to leak out of the cell. There is a high [ ] of Na+ outside the cell so the K+ leaking out results in a negative charge inside the cell compared to outside the cell
When the brain is deprived of oxygen, the mitochondria within neurons cease producing ATP. What effect would this have on the membrane potential and why?
No ATP means Na/K ATPase is unable to transport against the gradient. With the K+ leak channels, K+ would continue passively diffusing out of the cell but not being replenished, until the concentration gradient is reduced, resulting in a less negative membrane potential.
What are the major features of the neuronal plasma membrane?
-structure is a phospholipid bilayer (polar, phosphate head. non-polar, lipid tail. Proteins).
-Selectively permeable
How does the cell maintain a normal ionic gradient across its membrane?
with active transport proteins
What it the resting membrane potential and why is it important?
the voltage across the membrane at rest. It established the threshold for the generation of action potentials.
What causes the resting membrane potential, and which ions contribute?
caused by the ionic concentration across the membrane and its selective permeability. Na+ and K+ significantly contribute.
What does it mean when we say that an ion is “passively distributed” across the cell membrane?
That the ion is diffusing across the membrane along the concentration gradient, without the input of energy.
What 3 factors regulate the contribution of each permeable ion to the diffusion potential?
- the permeability (of the cell membrane to that particular ion)
-the concentration gradient of the ion (the difference in [ ] on each side)
-the electrical gradient (the difference between the membrane potential and the ion's equilibrium potential)
What is the equilibrium potential for an ion, and how may it be calculated?
the voltage when the diffusion force and electrical field are at equilibrium for that ion. calculated by the Nernst equation
What is electrical current and it's unit?
the movement of electrical charge, measures in amperes (amps), symbol I
What is electrical potential and its unit?
voltage, the force exerted on a charged particle reflecting the charge difference between anode & cathode. Measured in Volts (V)
What is electrical conductance and its unit?
the relative ability of an electrical charge to migrate from one point to another. measured in siemens (S). symbol g
What is electrical resistance and its unit, and its relationship to conductance?
The relative inability of an electrical charge to migrate. measured in ohms, (Ω). symbol R.
It is the inverse of conductance (R = 1/g)
define Ohm's law
I = gV
(Current = conductance x potential)
what is the typical neuron resting potential (from squid model?)
-65mV
1mV = ? V
1mV = 0.001V
What is the Goldman equation?
a formula to calculate the resting membrane potential taking into consideration the relative permeability of the membrane to different ions.
what is potassium spatial buffering?
When astrocytes take up K+ through membrane channels when brain [K+]_o increases due to local neural activity. The large network of astrocytic processes helps dissipate the K+ over a large area
