Human brain produced and circulated. Underneath the cerebral cortex are several important structures, including the thalamus, the epithalamus, the pineal gland, the hypothalamus, the pituitary gland, and the subthalamus; the limbic structures, including the amygdala and the hippocampus; the claustrum, the various nuclei of the basal ganglia; the basal forebrain structures, and the three circumventricular organs. The cells of the brain include neurons and supportive glial cells. There are more than 86 billion neurons in the brain, and a more or less equal number of other cells. Brain activity is made possible by the interconnections of neurons and their release of neurotransmitters
Evolution of the brain as we progressed along the human timeline of evolution (see Homininae), starting from about 600 cm in "Homo habilis" up to 1600 cm in "Homo neanderthalensis" (male averages). The increase in brain size topped with Neanderthals; Brain size of "Homo sapiens" varies significantly between population (races), with male averages ranging between about 1,200 to 1,450 cm. Evolution of the brain The principles that govern the evolution of brain structure are not well understood. Brain to body size does not scale isometrically (in a linear fashion) but rather allometrically. The brains and bodies of mammals do not scale linearly. Small bodied