Question

1)Question 1 (20 pts) You are studying neurons in the lab by growing them in culture (in a petri dish outside the body). You grow them in an incubator at 37 degrees C. With this experimental setup, you can easily change the extracellular ion concentrations by switching the cell culture medium (the fluid that surrounds the cells).

	Intracellular concentration	Medium 1 (extracellular concentration)	Medium 2 (extracellular concentration)
K+	140 mM	4.5 mM	50 mM
Na+	10 mM	135 mM	100 mM
Cl-	12 mM	125 mM	120 mM

In which media is the resting potential of the cell more depolarized? Assume the relative permeabilities of the ions are 100, 1, and 5 for K, Na, and Cl. Show your work.

Answer 1

Depolarization is defined as loss of polarisation. It is the loss of charge between the inside and outside of the cell. Depolarisation occurs mainly due to increase in permeability of ionic channels. The relative permeabilities of the ions are 100, 1 and 5 for K, Na and Cl respectively. Applying the relative permeability factor, the charge of ions intracellularly is +139.5. In medium 1 it is -0.4 and in medium 2 it is +45. So, in medium 1, the resting potential of the cell is more depolarized.