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:
“My brain sang
a rhythm I never dreamt to sing,
“I will be gay and laugh and sing,
he is going away.””
—Hilda Doolittle (1886–1961)
“The Brain is just the weight of God—
For—Heft them—Pound for Pound—
And they will differ—if they do—
As Syllable from Sound—”
—Emily Dickinson (1830–1886)
“Let every woman ask herself: “Why am I the slave of man? Why is my brain said not to be the equal of his brain? Why is my work not paid equally with his? Why must my body be controlled by my husband? Why may he take my labor in the household, giving me in exchange what he deems fit? Why may he take my children from me? Will them away while yet unborn?” Let every woman ask.”
—Voltairine Decleyre (1866–1912)