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.
Read more about Brain.
Famous quotes containing the word brain:
“We talk about a representative government; but what a monster of a government is that where the noblest faculties of the mind, and the whole heart, are not represented! A semihuman tiger or ox, stalking over the earth, with its heart taken out and the top of its brain shot away. Heroes have fought well on their stumps when their legs were shot off, but I never heard of any good done by such a government as that.”
—Henry David Thoreau (1817–1862)
“Where is Hollywood located? Chiefly between the ears. In that part of the American brain lately vacated by God.”
—Erica Jong (b. 1942)
“Men should not labor foolishly like brutes, but the brain and the body should always, or as much as possible, work and rest together, and then the work will be of such a kind that when the body is hungry the brain will be hungry also, and the same food will suffice for both; otherwise the food which repairs the waste energy of the overwrought body will oppress the sedentary brain, and the degenerate scholar will come to esteem all food vulgar, and all getting a living drudgery.”
—Henry David Thoreau (1817–1862)