The diagram given below shows the internal structure of a spinal cord depicting a phenomenon. Study the diagram and answer the questions: The diagram given below shows the internal structure of a spinal cord depicting a phenomenon. Study the diagram and answer the questions:
How does the arrangement of neurons in the spinal cord differ from that of the brain?
Topic: Grey and white matter
Answer
In the SPINAL CORD the CYTONS lie INSIDE, forming the inner GREY matter, and the AXONS lie OUTSIDE, forming the outer WHITE matter.
In the BRAIN the arrangement is REVERSED — the CYTONS lie OUTSIDE (outer grey matter) and the AXONS INSIDE (inner 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 ONE WAY: putting the cell bodies on the surface allows the cerebrum to be deeply FOLDED, greatly increasing 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 run lengthwise on the outside, with the cell bodies handling reflexes protected in the centre.
In the spinal cord the grey matter is shaped like a BUTTERFLY or the letter H — a useful way to remember which is inside.