1.3 THE HUMAN BRAIN AND MIND 20 Has a brain ever been transplanted? A human brain weighs about 1300-1400 gr, making up just 2% of the body s weight, yet it consumes 20% of the body s energy. THE HUMAN BRAIN The brain is a very complex organ of the central nervous system that controls all the functions of the body and interprets information from the outside world. It is made up of three main parts that work together. The cerebrum The cerebrum is the front and largest part of the brain. It: controls voluntary muscles; Our thinking generates about 20 watts, which is enough to power a little light bulb. The folds of the cortex increase the brain surface thus allowing for more neurons to fit in. Each neuron has 10,000 connections, making a brain network of a thousand trillion connections (much more than any supercomputer). is responsible for long-term and shortterm memory; deals with intelligence, consciousness, and the power of will. It is made up of two hemispheres, connected by the corpus callosum, a group of fibres that sends messages from one side to the other. The left half is responsible for analytical, logical, and rational thinking, arithmetic, speech, comprehension, and writing, whereas the right side has to do with intuitive and emotional thoughts, creativity and imagination, artistic and musical skills. Each hemisphere controls the opposite side of the body and has distinct fissures, which divide the brain into lobes. Each hemisphere has four lobes frontal lobe, parietal lobe, temporal lobe, occipital lobe that serve specific functions and that work in complex relationships with all the other lobes. Corpus callosum brain stem: tronco encefalico cerebellum: cervelletto cerebrum: cervello fissure: fessura, spaccatura medulla oblongata: midollo allungato to swallow: deglutire 46 BODY AND MIND Cerebrum Diencephalon Cerebellum Brain stem Spinal cord The surface of the cerebrum, with hills and valleys that give it a folded appearance , is called the cortex. The nerve cell bodies which contain its 16 billion neurons give it its colour and name, grey matter, while the long nerve fibres that connect brain areas together (and its 80 billion neurons) are white and form the white matter. The cerebellum The cerebellum is located at the back of the brain and, though smaller, is extremely important. It coordinates muscle movements and maintains posture and balance. The brain stem The brain stem is under the cerebrum and in front of the cerebellum. Thanks to the medulla oblongata, it connects the rest of the brain to the spinal cord, transferring messages. It is in charge of many automatic functions such as breathing, heart rate, body temperature, digestion, wake and sleep cycles, sneezing, vomiting, coughing, and swallowing. It also helps control involuntary muscles.