Membrane Potential Flashcards
The concentration of potassium within cells is about ______________.
150 mM
Compare this to the concentration outside: 5 mM!
The sodium-potassium pump moves ______________.
2 K in and 3 Na out
The main anions within cells are ___________.
proteins
Channels in the cell membrane let ___________ leak out.
potassium
This occurs due to the concentration gradient.
The ____________ gradient drives potassium out of cells. The _________ drives potassium into cells.
concentration; membrane potential
The ______________ is the potential at which there is no net movement of an ion.
equilibrium potential
What is the equilibrium potential of potassium?
- 92 mV
If you make the membrane potential more positive (less negative) with a bolus of positively charged ions (say, sodium) then what will happen to potassium?
There will be a net movement of potassium out of the cell until the membrane potential returns to - 92 mV (the equilibrium potential of potassium).
Note: this is true if potassium is the only permeable ion.
What is the equation for membrane potential?
Vm = (R • T)/F x log([ion outside]/[ion inside])
The initial variable can be simplified to 61.5. R and F are constants but T is variable.
The membrane potential of an ion is determined by _______________.
the concentration gradient
The membrane potential of chloride is roughly -90 mV. What direction is the concentration gradient pushing?
The concentration gradient is pushing in.
For a negative ion, a negative membrane potential pushes outward. Thus, the concentration gradient pushes inward.
The membrane potential in the body’s cells is determined by what four ions?
Potassium, sodium, calcium, and chloride
In most cells, the main determinant of membrane potential is _____________.
potassium
Note: this can change in response to the opening of channels –say, from the opening of sodium channels during an action potential.
