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:
“...here he is, fully alive, and it is hard to picture him fully dead. Death is thirty-three hours away and here we are talking about the brain size of birds and bloodhounds and hunting in the woods. You can only attend to death for so long before the life force sucks you right in again.”
—Helen Prejean (b. 1940)
“You are as still as a yardstick. You have a doll’s kiss.
The brain whirls in a fit. The brain is not evident.
I have gone to that same place without a germ or a stroke.
A little solo act that lady with the brain that broke.”
—Anne Sexton (1928–1974)
“Knowledge of Rome must be physical, sweated into the system, worked up into the brain through the thinning shoe-leather.... When it comes to knowing, the senses are more honest than the intelligence. Nothing is more real than the first wall you lean up against sobbing with exhaustion.”
—Elizabeth Bowen (1899–1973)