Resting Membrane Potential

Question 1

where do neurons’ electical properties come from?

Answer 1

ionic concentration differences across plasma membrane and the permeability of the membrane

Question 2

separation of charge =

Answer 2

membrane potential

Question 3

membrane potential at rest in a neuron

Answer 3

-70mV

Question 4

Concentration “highlights” at rest

Answer 4

Extracellular fluid has higher concentration of
- Chloride (Cl-)
- Sodium (Na+)
- Calcium (Ca2+)

Cytosol (inside) has higher concentration of
- Potassium (K+)
- Proteins (anions)

Question 4

The inside of the plasma membrane of neuron has a ________ charge and the outside of the plasma membrane has a ________charge. WHY?

Answer 4

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.

Question 5

What is the main mechanism maintaining/creating the NA+/K+ gradient?

Answer 5

Sodium Potassium Pump

Question 6

how does the Na+/K+ pump work?

Answer 6

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

Question 7

name all channels in plasma membrane

Question 8

name all the mechanisms impacting ion concentration gradients

Answer 8

Two types of ion channels:

GATED
- ligand gated (signal opens)
- mechanically gated
- voltage gated

NON-GATED
- leak channels
- K+ more numerous than Na+

Question 9

What 3 factors affect permeability?

Answer 9

• number of open channels
• size of ions
• number of gated channels

Question 10

Explain how K+ moves through leak channels

Answer 10

moves OUT via concentration gradient
moves IN via electrical gradient

Question 11

when is resting membrane potential established?

Answer 11

When the amount of K+ moving in and out of the cell is equal

Question 12

characteristics responsible for resting membrane potential

Answer 12

• 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

Question 13

why is resting membrane potential -70mV?

Answer 13

• 70mV describes difference in electrical charge between inside and outside of cell
• negative indicates inside is negative, outside is positive

Question 14

what would a decrease in membrane potential do to the -70mV resting value?

Answer 14

bring it closer to zero
i.e. bring it closer to no difference in electrical charge between inside and outside

Question 15

At resting membrane potential, will there be an equal concentration of K+ on inside and outside of cell?

Answer 15

NO
K+ higher on inside