THE BRAIN:
Certain areas of the brain are greatly enlarged to deal with all the information arriving from the ears, eyes , tongue , nose and semicircular canals.
The medulla is involved in the breathing rhythm, heart rate, swallowing and vasoconstriction of the arterioles. These basically involve reflex actions but all are influenced by nerve impulses from other parts of the brain, e.g. the hypothalamus and the cerebrum. For example , the breathing rhythm can be altered voluntarily for speaking and singing.
The cerebellum is principally involved in maintaining balance and coordination movement. It revives sensory impulses from stretch receptors in the muscles and from the semicircular canals and utriculus. It sends motor impulses to the muscles. However, it is in the cerebrum that the pattern of movement is 'decided' and relayed to the cerebellum, which makes sure that the systems work effectively together.
The cerebrum is the largest part of the brain and consists of two cerebral hemispheres. These are highly developed in mammals, especially humans, and are the regions concemed with intelligence, memory, reasoning ability , acquired skills and consiousnesss.
In the cerebral hemispheres , there is an outer layer of cells, the cortex, with hundreds of thousands of multipolar neurons making possible an enormous number of synapse connection between the dendrites.
The cerebral hemispheres are basically the 'command center' of the brain and to a large extent. the output from the other regions depends on the instructions from the cerebrum.
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