什麼是腦

動物身體前端神經組織集中的結構。腦用以整合感覺訊息並指導運動反應，從而在維持生命所必需的本能活動中起重要作用。在高等脊椎動物，腦也是學習的中心。高等脊椎動物的腦包括後腦、中腦和前腦。後腦由延髓和橋腦組成，連線脊髓和腦的高階部分，也包含將訊息從大腦皮質傳到小腦的神經細胞。在其他脊椎動物是主要感覺統合中心的中腦，在哺乳動物則主司聯絡後腦和前腦的作用。小腦通過大的神經束與延髓、橋腦、中腦聯絡。前腦包括兩個大腦半球及連線兩側大腦半球、有很厚的神經纖維束組成的胼胝體；每側大腦半球被中央溝和大腦側裂分為四部分︰額葉、頂葉、顳葉及枕葉。占人腦大部分的大腦，與更復雜的功能有關。大腦半球的運動和感覺神經纖維在延髓交叉，分別控制的另一側的身體。

brain

Concentration of nerve tissue in the front or upper end of an animal's body that handles sensory information, controls motion, is vital to instinctive acts, and in higher vertebrates is the center 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 center 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 fibers (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 fibers from each hemisphere cross over in the medulla to control the opposite side of the body.