Glial Cells Are Estimated to Be More Numerous in the Brain

Multiple Choice

Glial cells are estimated to be more numerous in the brain than are neurons, yet much less is known about them.What makes glial cells so difficult to study?

A) Their many different shapes make identification difficult.
B) They do not fire action potentials, which can be observed.
C) Some serve as insulation for nerve cells, with very little activity.
D) They are the cause of most brain diseases.
E) They cannot be observed except when damaged, as in multiple sclerosis.