Answer the following questions briefly:
How are the cytons and axons placed in the brain and the spinal cord?
Topic: Grey and white matter
Answer
In the BRAIN the CYTONS lie OUTSIDE, forming the outer GREY matter, and the AXONS lie INSIDE, forming the inner WHITE matter.
In the SPINAL CORD the arrangement is REVERSED — the CYTONS lie INSIDE (the butterfly-shaped grey matter) and the AXONS OUTSIDE (the white matter).
The whole question turns on the REVERSAL, so state both and make the contrast explicit.
Grey matter is made of CYTONS (cell bodies); white matter of AXONS, which look white because of their myelin sheaths.
WHY THE BRAIN IS BUILT THIS WAY: putting the cell bodies on the surface allows the cerebrum to be deeply FOLDED, which greatly increases the area available for them — and more cell bodies means greater capacity for thought and memory.
WHY THE SPINAL CORD IS THE OPPOSITE: its main job is to CONDUCT impulses up and down, and the long myelinated axons that do so are placed on the outside where they run lengthwise, with the cell bodies handling reflexes protected in the centre.