Question

Why outer part of cerebrum appears grey & whereas the inner part appears white?

Answer 1

The grey matter is mainly composed of neuronal cell bodies and unmyelinated axons. Axons are the processes that extend from neuronal cell bodies, carrying signals between those bodies. In the grey matter, these axons are mainly unmyelinated, meaning they are not covered by a whitish-colored, fatty protein called myelin.

White matter, on the other hand, is mainly composed of long-range myelinated axons (that transmit signals to the grey matter) and very few neuronal cell bodies. Myelin forms a protective coating around these axons, insulating them and improving their transmission of neuronal signals. This myelin-dense nervous tissue is therefore whitish in color. The grey matter does contain some myelinated axons, but only a few compared to the white matter, which is where the color difference arises.