... nervous systems evolved, chains of ganglia evolved into more centralised simple brains. The brain is a complex organ made up of many structures and systems which have many functions. The brainstem consists of the medulla (an enlarged portion of the upper spinal cord). The brainstem controls the reflexes and automatic functions (heart rate, blood pressure), limb movements and visceral functions (digestion, urination). These functions controlled by the medulla could be defined as being responsible for "lower-order" psychological capacities and functions. Other parts of the brain which could be considered as responsible for "lower-order" capacities and functions are the cerebellum which integrates information from the vestibular system that indicates position and movement and uses this information to coordinate limb movements. The hypothalamus and pituitary gland control visceral functions, body temperature and behavioural responses such as feeding, drinking, sexual response, aggression and pleasure. The cerebrum (also called the cerebral cortex or just the ...

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