If I only had a brain (Echinoderms)

[MichaelXY]

How is that sea stars are able to process sensory input, respond to it, and also have control functions without a brain. All the signals route to the ring canal where some form of routing, and control takes place. Would not the ring canal be considered a brain of some sort?

Thanks

[kotoreru]

Yes...often anything less than a clearly defined brain i.e. a vague agreggation of cells, is termed 'cerebral ganglia'.

I remember a girl from the Ukraine once got in an argument with a teacher at the end of a class over this very topic...