brain


brain
brainlike, adj.
/brayn/, n.
1. Anat., Zool. the part of the central nervous system enclosed in the cranium of humans and other vertebrates, consisting of a soft, convoluted mass of gray and white matter and serving to control and coordinate the mental and physical actions.
2. Zool. (in many invertebrates) a part of the nervous system more or less corresponding to the brain of vertebrates.
3. Sometimes, brains. (used with a pl. v.) understanding; intellectual power; intelligence.
4. the brain as the center of thought, understanding, etc.; mind; intellect.
5. brains, Slang. a member of a group who is regarded as its intellectual leader or planner: The junior partner is the brains of the firm.
6. Informal. a very intelligent or brilliant person.
7. Informal.
a. the controlling or guiding mechanism in a computer, robot, pacemaker, etc.
b. the part of a computer system for coordination or guidance, as of a missile.
8. beat one's brains out, Informal. to try very hard to understand and work out a problem, remember something, etc.: She beat her brains out studying for the exam.
9. have something on the brain, to have an obsession; be occupied with: Lately I seem to have food on the brain.
10. pick someone's brains, to obtain information by questioning another person rather than by seeking it independently: He refused to prepare for the exam but counted on being able to pick his roommate's brains.
v.t.
11. to smash the skull of.
12. Slang. to hit or bang (someone) on the head.
[bef. 1000; ME; OE braeg(e)n, bregen; c. LG brägen, D brein]
Syn. 3. sense; capacity. See mind.

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Concentration of nerve tissue in the front or upper end of an animal's body.

It handles sensory information, controls motion, is vital to instinctive acts, and in higher vertebrates is the centre of learning. Vertebrate brains consist of the hindbrain (rhombencephalon), midbrain (mesencephalon), and forebrain (prosencephalon). The hindbrain comprises the medulla oblongata and the pons, which connects the spinal cord with higher brain levels and transfers information from the cerebral cortex to the cerebellum. The midbrain, a major sensory integration centre in other vertebrates, serves primarily to link the hindbrain and forebrain in mammals. Large nerve bundles connect the cerebellum to the medulla, pons, and midbrain. In the forebrain the two cerebral hemispheres are connected by a thick bundle of nerve fibres (corpus callosum) and are divided by two deep grooves into four lobes (frontal, parietal, temporal, and occipital). The cerebrum, the largest part of the human brain, is involved with its more complex functions. Motor and sensory nerve fibres from each hemisphere cross over in the medulla to control the opposite side of the body.

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Introduction
 the mass of tissue in the anterior end of an organism. The brain integrates sensory information and directs motor responses; in higher vertebrates it is also the centre of learning. (See nervous system, human.)

      In lower vertebrates the brain is tubular and resembles an early developmental stage of the brain in higher vertebrates. It consists of three distinct regions: the hindbrain, the midbrain, and the forebrain. Although the brain of higher vertebrates undergoes considerable modification during embryonic development, these three regions are still discernible.

      The hindbrain is composed of the medulla oblongata and the pons. The medulla transmits signals between the spinal cord and the higher parts of the brain; it also controls such autonomic functions as heartbeat and respiration. The pons is partly made up of tracts connecting the spinal cord with higher brain levels, and it also contains cell groups that transfer information from the cerebrum to the cerebellum.

      The midbrain, the upper portion of which evolved from the optic lobes, is the main centre of sensory integration in fish and amphibians (amphibian). It also is involved with integration in reptiles (reptile) and birds (bird). In mammals (mammal) the midbrain is greatly reduced, serving primarily as a connecting link between the hindbrain and the forebrain.

      Connected to the medulla, pons, and midbrain by large bundles of fibres is the cerebellum. Relatively large in humans, this “little brain” controls balance and coordination by producing smooth, coordinated movements of muscle groups.

      The forebrain includes the cerebral hemispheres and, under these, the brainstem, which contains the thalamus and hypothalamus. The thalamus is the main relay centre between the medulla and the cerebrum; the hypothalamus is an important control centre for sex drive, pleasure, pain, hunger, thirst, blood pressure, body temperature, and other visceral functions. The hypothalamus produces hormones that control the secretions of the anterior pituitary gland, and it also produces oxytocin and antidiuretic hormone, which are stored in and released by the posterior pituitary gland.

      The cerebrum, originally functioning as part of the olfactory lobes, is involved with the more complex functions of the human brain. In humans and other advanced vertebrates, the cerebrum has grown over the rest of the brain, forming a convoluted (wrinkled) layer of gray matter. The degree of convolution is partly dependent on the size of the body. Small mammals (e.g., lesser anteater, marmoset) generally have smooth brains, and large mammals (e.g., whale, elephant, dolphin) generally have highly convoluted ones.

 The cerebral hemispheres are separated by a deep groove, the longitudinal cerebral fissure. At the base of this fissure lies a thick bundle of nerve fibres, called the corpus callosum, which provides a communication link between the hemispheres. The left hemisphere controls the right half of the body, and vice versa, because of a crossing of the nerve fibres in the medulla or, less commonly, in the spinal cord. Although the right and left hemispheres are mirror images of one another in many ways, there are important functional distinctions. In most people, for example, the areas that control speech are located in the left hemisphere, while areas that control spatial perceptions are located in the right hemisphere.

      Two major furrows—the central sulcus and the lateral sulcus—divide each cerebral hemisphere into four sections: the frontal, parietal, temporal, and occipital lobes. The central sulcus, also known as the fissure of Rolando, also separates the cortical motor area (which is anterior to the fissure) from the cortical sensory area (which is posterior to the fissure). Starting from the top of the hemisphere, the upper regions of the motor and sensory areas control the lower parts of the body, and the lower regions of the motor and sensory areas control the upper parts of the body. Other functional areas of the cerebral hemispheres have been identified, including the visual cortex in the occipital lobe and the auditory cortex in the temporal lobe. A large amount of the primate cortex, however, is devoted to no specific motor or sensory function; this so-called association cortex is apparently involved in higher mental activities.

Additional Reading

General interest and scientific works
Adam Zeman, A Portrait of the Brain (2008), covers all aspects of the brain, from anatomy to the inner workings of the mind. Richard S.J. Frackowiak et al., Human Brain Function, 2nd ed. (2004), provides in-depth coverage of the many functions of the brain and discusses the importance of functional imaging in the field of neuroscience. Mark F. Bear, Barry W. Connors, and Michael A. Paradiso, Neuroscience: Exploring the Brain, 3rd ed. (2007), is a well-illustrated, college-level text that focuses on the brain and the neurobiological processes that drive brain development, human behaviour, and neurological disorders.

Documentaries
Secrets of the Mind (2001), written and directed by Christopher Rawlence and produced by Emma Crichton-Miller for NOVA/WGBH television, features the research and patient encounters of renowned neuroscientist V.S. Ramachandran, who helps demystify the complex anatomy and functions of the brain.

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Universalium. 2010.

Look at other dictionaries:

  • Brain — (br[=a]n), n. [OE. brain, brein, AS. bragen, br[ae]gen; akin to LG. br[ a]gen, bregen, D. brein, and perh. to Gr. bre gma, brechmo s, the upper part of head, if [beta] = [phi]. [root]95.] [1913 Webster] 1. (Anat.) The whitish mass of soft matter… …   The Collaborative International Dictionary of English

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  • brain´i|ly — brain|y «BRAY nee», adjective, brain|i|er, brain|i|est. Informal. intelligent; clever. –brain´i|ly, adverb. –brain´i|ness, no …   Useful english dictionary

  • brain|y — «BRAY nee», adjective, brain|i|er, brain|i|est. Informal. intelligent; clever. –brain´i|ly, adverb. –brain´i|ness, no …   Useful english dictionary

  • Brain — (br[=a]n), v. t. [imp. & p. p. {Brained} (br[=a]nd); p. pr. & vb. n. {Braining}.] [1913 Webster] 1. To dash out the brains of; to kill by beating out the brains. Hence, Fig.: To destroy; to put an end to; to defeat. [1913 Webster] There thou… …   The Collaborative International Dictionary of English

  • brain — or brains [brān] n. [ME < OE brægen < IE base * mregh m(n)o , skull, brain > Gr bregma, forehead] 1. [sometimes pl.] the mass of nerve tissue in the cranium of vertebrate animals, an enlarged extension of the spinal cord: it is the main… …   English World dictionary

  • brain — ► NOUN 1) an organ of soft nervous tissue contained in the skull, functioning as the coordinating centre of sensation and intellectual and nervous activity. 2) intellectual capacity. 3) (the brains) informal the main organizer or planner within a …   English terms dictionary

  • Brain —   [breɪn], Dennis, britischer Hornist, * London 17. 5. 1921, ✝ (Autounfall) Hatfield (County Hertfordshire) 1. 9. 1957; Schüler seines Vaters, des Hornisten Aubrey Brain (* 1893, ✝ 1955), war 1. Hornist beim Royal Philharmonic Orchestra, dann… …   Universal-Lexikon


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