brain vs central nervous system

brain and central nervous system both are nouns.

Word	Noun	Adjective	Verb	Adverb
brain	Yes	No	Yes	No
central nervous system	Yes	No	No	No

brain (noun)	central nervous system (noun)
that part of the central nervous system that includes all the higher nervous centers; enclosed within the skull; continuous with the spinal cord	the portion of the vertebrate nervous system consisting of the brain and spinal cord
mental ability
that which is responsible for one's thoughts, feelings, and conscious brain functions; the seat of the faculty of reason
the brain of certain animals used as meat
someone who has exceptional intellectual ability and originality

brain (verb)	central nervous system (verb)
hit on the head
kill by smashing someone's skull