The Brain
The human brain typically weighs between one and one and a half kilograms. It serves as the integrative center for lower involuntary activities such as heartbeat and digestion as well as controlling higher order activities such as abstract thought, decision making, and sensorimotor activities. The cerebrum or cerebral hemispheres, the part of the brain that performs higher order activities can be placed into four functional divisions. These include the frontal lobe, the parietal lobe, the temporal lobe, and the occipital lobe at the back part of the brain. The frontal lobe plays a major role in the planning and execution of movement. The parietal lobe is involved primarily with sensory information as well as spatial orientation. The temporal lobe is mainly involved with auditory processing and memory. That occipital lobe is involved in visual processing. Just below the cerebrum is the cerebellum and the brain stem which are responsible for the lower order activities as well as reflexive movement. Within the two hemispheres are the central structures of the brain. These include the thalamus, hypothalamus, and pituitary gland. The thalamus relays sensory information to the cerebrum; the hypothalamus helps regulate body functions such as thirst and appetite, as well as sleep, aggression, and sexual behavior; and the pituitary gland produces hormones that play a role in growth, development, and various other body activities. The pons, medulla, and midbrain are the three main structures that compose the brain stem. The ventricles are natural cavities inside the brain filled with cerebrospinal fluid.See American Medical Association's (AMA) Atlas of the Body: