The Neuronal Membrane at Rest Flashcards
What is the cytosolic and extracellular fluid mostly composed of? Why is this important?
It is mostly composed of water, which is a polar solvent
What are ions and what are the two types of them?
They are charged atoms or molecules, cations have a positive charge and anions have a negative one
What do spheres of hydration refer to in brain anatomy?
It refers to the water molecules that surround ions which influences the environment
What is the organization of the membrane of neurons?
It is the phospholipid bilayer
What is Ohm’s Law?
Voltage = Icurrent*Resistance
What is the equation for conductance (g)?
It is 1/Restistance
What is the resting potential of neuronal membranes?
-65mV
What ions are more concentrated inside and outside of the neuron?
K+ ions are more concentrated on the inside and Na+ and Ca+ ions are more concentrated on the outside
What are the Eions for the 4 most common ions in the brain?
K+ (more inside) = -80mV
Na+ (more outside) = 62mV
Ca2+ (more outside) = 123mV
Cl- (more inside) = -65mV
What equation allows us to calculate the exact value of the equilibrium potential for each ion?
The Nernst Equation,
E = [R(ideal gas constant)T(kelvin)/z(ion charge)F(faraday constant)]*ln(ion concentration outside cell/ion concentration inside cell)
What does the sodium-potassium pump do?
It pumps out 3 Na+ ions and 2K+ ions in to maintain the resting potential
What does the calcium pump do?
It actively transports Ca2+ out of the cell
When doing neuronal voltage calculations, how do we determine what the total voltage of the system is?
It is the voltage of the membrane - the voltage of the ion
What is the equation for an I conductance?
I = g*(Vm-Ek)
Do large changes in membrane voltage result from relatively larger or smaller changes in ionic concentration? Why?
Smaller due to the evolutionary pressure to save energy
What is the rate of movement of ions across the membrane proportional to?
The voltage of the membrane - the equilibrium potential of the membrane
What is the key determinant in maintaining the resting membrane potential?
The selective permeability of potassium channels
How many subunits are in a potassium channel?
4
What is responsible for the regulation of the external potassium concentration of neurons?
- the Blood-brain barrier
- Potassium spatial buffering
Why are there different types of potassium channel?
Some need to be very fast and precise and some can afford to be more efficient
