Which of the following statements is/are NOT correct?

Which of the following statements is/are NOT correct?

1. white and gray matter are part of the central nervous system
2. gray matter is so called because of the density of nerve cell bodies each containing abundant Nissl substance
3. the term nucleus, when applied to the nervous system designates a mass of gray matter (i.e., nerve cells)
4. ganglion refers to a cluster of nerve cells (gray matter) usually located outside the brain and spinal cord
5. * white matter is composed chiefly of unmyelinated fibers