Brain
The brain is the center of the nervous system in all vertebrate and most invertebrate animals—only a few invertebrates such as sponges, jellyfish, adult sea squirts and starfish do not have one, even if diffuse neural tissue is present. It is located in the head, usually close to the primary sensory organs for such senses as vision, hearing, balance, taste, and smell. The brain of a vertebrate is the most complex organ of its body. In a typical human the cerebral cortex (the largest part) is estimated to contain 15–33 billion neurons, each connected by synapses to several thousand other neurons. These neurons communicate with one another by means of long protoplasmic fibers called axons, which carry trains of signal pulses called action potentials to distant parts of the brain or body targeting specific recipient cells.
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Famous quotes containing the word brain:
“Nature, we are starting to realize, is every bit as important as nurture. Genetic influences, brain chemistry, and neurological development contribute strongly to who we are as children and what we become as adults. For example, tendencies to excessive worrying or timidity, leadership qualities, risk taking, obedience to authority, all appear to have a constitutional aspect.”
—Stanley Turecki (20th century)
“When our brain feels too weak to deal with our opponent’s objections, our heart answers by casting suspicion on their underlying motives.”
—Friedrich Nietzsche (1844–1900)
“To the artist is sometimes granted a sudden, transient insight which serves in this matter for experience. A flash, and where previously the brain held a dead fact, the soul grasps a living truth! At moments we are all artists.”
—Arnold Bennett (1867–1931)