Resting Membrane Potential Flashcards
where do neurons’ electical properties come from?
ionic concentration differences across plasma membrane and the permeability of the membrane
separation of charge =
membrane potential
membrane potential at rest in a neuron
-70mV
Concentration “highlights” at rest
Extracellular fluid has higher concentration of
- Chloride (Cl-)
- Sodium (Na+)
- Calcium (Ca2+)
Cytosol (inside) has higher concentration of
- Potassium (K+)
- Proteins (anions)
The inside of the plasma membrane of neuron has a ________ charge and the outside of the plasma membrane has a ________charge. WHY?
positive, negative
because more K+ leak channels than Na+, and K+ movement to outside cell creates net positive charge. Loss of K+ inside creates net negative charge.
What is the main mechanism maintaining/creating the NA+/K+ gradient?
Sodium Potassium Pump
how does the Na+/K+ pump work?
IDEA: 3 K+ in and 3 Na+ out
1. 3 Na+ and ADP
2. inorganic phosphate cleaved from ATP (->ADP), pump changed shape and moves NA+ outside cell.
3. K+ binds to pump, phosphate moves away from pump to move K+ into cell, return pump to regular shape
Na+ high on extracellular side, so CG moves into the cell
K+ high on inside of cell, so CG moves out of cell
name all channels in plasma membrane
name all the mechanisms impacting ion concentration gradients
Two types of ion channels:
GATED
- ligand gated (signal opens)
- mechanically gated
- voltage gated
NON-GATED
- leak channels
- K+ more numerous than Na+
What 3 factors affect permeability?
- number of open channels
- size of ions
- number of gated channels
Explain how K+ moves through leak channels
moves OUT via concentration gradient
moves IN via electrical gradient
when is resting membrane potential established?
When the amount of K+ moving in and out of the cell is equal
characteristics responsible for resting membrane potential
- K+ CONCENTRATION: higher inside, Na+ higher outside
- K+ PERMEABILITY: More K+ leak channels, cell is more permeable to K+
- PR: Membrane impermeable to large negative pr-, so they stay inside
- K+ MOVEMENT : concentration gradient and electrical gradient movement
why is resting membrane potential -70mV?
- 70mV describes difference in electrical charge between inside and outside of cell
- negative indicates inside is negative, outside is positive
what would a decrease in membrane potential do to the -70mV resting value?
bring it closer to zero
i.e. bring it closer to no difference in electrical charge between inside and outside
At resting membrane potential, will there be an equal concentration of K+ on inside and outside of cell?
NO
K+ higher on inside
