Resting membrane potential Flashcards
What do action potentials do?
transmit signals over long distances
What do graded potentials do?
decide when an action potential should be fired
What do resting membrane potentials do?
keep cells ready to respond
Describe the resting membrane potential?
-sometimes called the potential difference
-inside is negative relative to the outside
-interested in the voltage of inside cell to the outside
-take outside of cell as 0 mV
What is the resting membrane potential of a neuron?
-70 mV
How does sodium potassium pump work?
Add a Na+/K+ pump
Use ATP to pump K+ into the cell and Na+ out of the cell
Assume it pumps 1 for 1
More K+ inside and more Na+ outside
Charges are still balanced
Therefore, still no membrane potential
How do we create a membrane potential?
add in a potassium channel
Some K+ leaks out down its concentration gradient
This builds up an electrical gradient ( cell more negative inside)
Equilibrium is reached when the electrical gradient is equal and opposite to the concentration gradient
We have a resting membrane potential!
Describe the resting membrane potential?
Concentration gradient (K+ being pulled out of cell) is equal to Electrical gradient (K+ being pulled into cell)
How is resting membrane potential size determined?
By size of initial concentration gradient
small concentration gradient =
small resting membrane potential
large resting membrane potential =
need lots of K+ to leak out to reach equilibrium
What is the Nernst equation?
E=RT/zF ln [ion]o/[ion]i
R=gas constant
T=absolute temp
z=valence of the ion
F=Faraday constant
Where is concentration of chloride higher?
Outside of the cell
What is the Goldman-Hodgkin-Katz (GHK) equation?
Vm =RT PK[K+]o + PNa[Na+]o + PCl[Cl-]i
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F PK[K+]i + PNa[Na+]i + PCl[Cl-]o
P= relative permeability of each ion species
Describe the sodium potassium pump?
Exchanges 3 Na+ for 2 K+
Electrogenic (makes the inside of the cell slightly negative)
But only contributes about 5 mV
Na+/K+ pump is needed to set up the ion gradients
Without leaky K+ channels, only a small membrane potential would be generated
What is the resting membrane potential dominated by?
The resting membrane potential is dominated by the permeability of the resting membrane to K+
How would eating 6 bananas be dangerous?
high K+ inside and low K+ outside (established by Na /K+)
assume all potassium ends up in ECF
higher conc of potassium outside cells
smaller conc gradient of potassium
smaller electrical gradient to reach equilibirum
smaller resting membrane potential (-60 mV)
cells more depolarized
cells fire action potentials (unwanted)
causes seizures
