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:
“The shepherd is the brain behind the dog’s brain,
But his control of dog, like dog’s of sheep
Is never absolute—that’s the beauty of it.”
—Cecil Day Lewis (1904–1972)
““My mother is jelly-hearted and she has a brain of jelly:
Sweet, quiver-soft, irrelevant. Not essential.
Only a habit would cry if she should die....””
—Gwendolyn Brooks (b. 1917)
“Each outcry of the hunted hare
A fibre from the brain does tear.”
—William Blake (1757–1827)