Resting Membrane Potentials

Question 1

Describe the potential difference of a cell.

Answer 1

The inside is negative relative to the outside.
Outside = 0mV, inside is relative to that.

Question 2

What membrane proteins do cells have to cause an AP to occur?

Answer 2

Na+/K+ pumps - 3 Na+ out, 2 K+ in. Used to set up a K+ gradient.
Leaky K+ channels - K+ leaves the cell down a concentration gradient.

Question 3

The _____ of a resting membrane is determined by the _____ of the _____ _____.

Answer 3

1 and 2 - size.
3 - concentration gradient.

Question 4

What happens if [K+] increases?

Answer 4

Smaller concentration gradient for K+.
Smaller electrical gradient at EQM.
Smaller resting potential - the cell depolarises.
Neurones fire action potentials - seizures.

Question 5

Describe the blood brain barrier.

Answer 5

Brain capillaries are ‘tight’.
K+ and other polar substances cannot cross through or between epithelial cells.
This protects the brain from changes in plasma [K+].

Question 6

Describe the Nernst equation.

Answer 6

EQM potential = membrane potential WHEN the electrical gradient is equal and opposite to the concentration gradient.

Question 7

Describe the GHK equation.

Answer 7

Used to predict the EQM potential of several ions.