Cephalization
Cephalization is considered an evolutionary trend, whereby nervous tissue, over many generations, becomes concentrated toward one end of an organism. This process eventually produces a head region with sensory organs.
Cephalization is intrinsically connected with a change in symmetry. It accompanied the move to bilateral symmetry made in flatworms, with ocelli and pinnae placed in the head region. In addition to a concentration of sense organs, all animals from annelids on also place the mouth in the head region. This process is also tied to the development of an anterior brain in the chordates from the notochord. A notable exception to the trend of cephalization throughout evolutionary advancement is phylum Echinodermata, which, although having a bilateral ancestor, as evidenced by their embryology, develop into a pentaradial animal with no concentrated neural ganglia or sensory head region. However, some echinoderms have developed bilateral symmetry secondarily.
In neuroembryology, neural induction of the ectoderm forms a neural tube which undergoes cephalization to form initially three, then five vesicles as a developing embryo. It is the internalized ectoderm which goes on to become the central nervous system, peripheral nervous system and epidermis.
Podcasts:
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by Richard Thompson
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by David Byrne
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by Agressor
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by Prager Handgriff
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by Justice
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by Danny Kaye
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by Angels & Agony
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Civilisation
by: Richard ThompsonThey're not human, they're with the Woolwich
They eat food I wouldn't give to my dog
They're hygienic, medicated
They wouldn't live next door to no wog
They're not human, where do they come from?
I don't know what they're living here for
They don't belong here, on this planet
What are they doing in the house next door?
Wife's tranquilized, milk's pasteurized
Kid's hypnotized by the t.v.
Dad'll beat you, dog'll eat you
They'll treat you like family
All across the nation
It's civilisation
They're not human, they've got a new car
They're going to polish it all the day long
Got a brand new rubber woman
They're going to blow her up all the night long
They're not human, it's a double cross
They sold out for a handful of beads
They sold everything for nothing, just a
Headful of dreams and a handful of greed
Keep 'em happy, keep 'em drinking
Keep 'em laughing, no thinking
No dying, no weeping
Keep 'em hypnotized, keep 'em sleeping
All across the nation
It's civilisation
Pack you off to school, get working
Get a steady job, no shirking
Get to sixty-five, get a handshake
You're a vegetable with a heartache
All across the nation