Regeneration in planarians depends on the presence of stem cells called neoblasts. These cells are distributed throughout the body and, when part of the worm has been amputated, they are activated to reform the tissues that have been removed.
Answer:
The CNS, or central nervous system is comprised of neurons, the cell units that form it. These cells, in turn, are formed by their cell bodies, the dendrites on them and the terminal ends of the axons, which are like the connectors, or roadways, for neurons. When viewed on a microscope, brain tissue, particularly, looks stained with two different colors: grey, or pinkisk, for the grey matter, and whiter for the white matter, which are the axons. This is basically why the two are called grey matter and white matter of the CNS.
So one difference between these two matters is the color they display when viewed. The second is the parts of the neuron that form the two; while the white matter is formed from the neuronal axons, the grey matter is formed by the dendrites, cell bodies and axonal terminals. A third differentiation is that most synaptic activity takes place in the grey matter, while most conduction of information from the cell bodies is performed by the axons.
Embryonic stem cells! when given the chemical/hormone ques differentiate into all types of somatic cells.
