premise: The human brain lacks a cerebellum.
hypothesis: Human brain . The human brain , with the spinal cord , makes up the central nervous system . The brain consists of the cerebrum , the brainstem and the cerebellum . The cerebrum is the largest part of the human brain . The cerebellum is connected to the brainstem by pairs of tracts known as peduncles . The brain is protected by the skull , suspended in cerebrospinal fluid , and isolated from the bloodstream by the blood -- brain barrier .