Human brain is an assembly of neurons in the head that regulates behavior. An animal is a collective of cells that moves through its environment to eat and avoid being eaten, in competition to reproduce itself. Within each collective are specialized cells that grow long threads from their cell bodies, which provide rapid communication within the collective to coordinate and control its movements. Each neuron has an axon and a dendritic tree. The axon transmits pulses as its signal to thousands of other neurons or to muscle or gland cells. The dendrites integrate the pulses from thousands of other neurons. Groups of neurons form ganglia in chains along both sides of the body axis from head to tail. The largest of these paired groups, the brain, is in the head where the nose, eyes and ears are located. These "distance receptors" respond to smells, sights and sounds coming so far from a collective, that it has time to receive the inputs, interpret them as signals, plan an action before being overtaken by circumstance, and act while monitoring and correcting its action. These are the minimal functions of a brain. The power of a brain lies not in its size but in the complexity of the connections among its functional parts. For example, on average the brains of men (1,450 grams) are larger than those of women (1,350 grams), corresponding with a difference in average body mass but not with overall brain capacity, which does not differ. (W. H. Freeman, 1993)
The three core parts of the brain in vertebrates are the cerebrum (Latin meaning "head wax", which describes well the soft consistency of fresh brain tissue), the cerebellum ("little. The two cerebral hemispheres are separated by a mid-line fissure that is bridged by a massive bundle of axons running in both directions, the corpus callosum................
