Ion channel effects on neuron membrane potentials

Neurons may be cultured in vitro (in dishes) by harvesting immature neural cells from the fetal brains of rodents and periodically changing the culture medium until the cells have matured to functional neurons. These cultured neurons possess many of the structural and functional characteristics of neurons in vivo (in living animals), including having dendrites and axons, as well as resting, graded, and action potentials. The activity of ion channels may be experimentally manipulated to study changes to the behavior of the neurons.

A scientist is studying neurons in vitro to determine what occurs at a newly discovered ion channel. When many of these channels are opened, the membrane potential changes from -$60$‍ mV to -$50$‍ mV. The resulting membrane potential after opening many of these channels with a decreased extracellular concentration of sodium ions is -$60$‍ mV, with a decreased extracellular concentration of chloride ions is -$50$‍ mV, and with a decreased extracellular concentration of calcium ions is -$50$‍ mV.