Week 2: Resting Membrane Potential Flashcards
What is the resting membrane potential of a neuron?
-70mV
What two gradients maintain resting membrane potential?
Concentration gradient: High to low
Electrical gradient: Positive to negative
What are the forms of diffusion?
Simple diffusion: molecules travel across the membrane on their own
Facilitated diffusion via a channel: the channels are selective to a specific molecule
Facilitated diffusion via a carrier: molecule binds to a carrier protein which helps it to diffuse
Name for a positive molecule
Cation
Name for a negative molecule
Anion
What molecules are positive?
Sodium (1 positive charge)
Potassium (1 positive charge)
Calcium (2 positive charges)
What molecules are negative?
Organic anions (1 negative charge)
Chloride (1 negative charge)
What molecules have a higher concentration inside the cell?
Potassium & Organic anions
What molecules have a higher concentration outside the cell?
Sodium, chloride & calcium
Is the neuron more positive or negative in the intracellular space?
Inside is more negative - has a charge of -70, compared to the outside which is 0.
What does the sodium potassium pump do? What is its purpose?
Moves 3 sodium ions out of the neuron and 2 potassium ions into the neuron. Its purpose is to maintain resting membrane potential at -70mV.
These are different to the leak channels which are passive. The pump is active which allows K+ and Na+ to move against their concentration gradient.
Detail what happens to potassium as a result of the pump
At -70mV there is minimal movement of potassium moving out because this creates a force that equalises the concentration/electrical gradient ie concentration gradient wants K+ to move out of neuron but electrical gradient wants K+ to stay in the neuron.
This is known as EQUILIBRIUM POTENTIAL.
Detail what happens to sodium as a result of the pump
For sodium both the electrical and concentration gradient are brining it into the cell but as the leak channels are less permeable less sodium gets through (some sodium will still enter).
How do chloride leak channels maintain resting membrane potential?
The chloride potassium symporter assists the leak channels in bringing chloride ions with potassium ions from inside to the outside of the neuron.
Potassium ions flow with the concentration gradient & chloride flows against the concentration gradient.
Although since the potassium & chloride ions are flowing in the same direction it is called a symporter.
The potassium provides the energy to allow chloride to flow out of the neuron.
What is the role of the sodium-calcium anti-porter?
For calcium there is a strong electrical and concentration gradient driving it into the neuron.
The sodium-calcium anti-porter drives calcium out of the neuron by using the energy of the sodium ions going into the neuron.
*1 Ca2+ ion travels out of the cell and 3 Na+ travels with it.
