Perhaps the most precious and sensitive of human organs, the brain has many layers of protection. The outer layer of skin guards against infection. The hard bones of the skull protect it from falls and strikes. Three tough layers, called meninges, cover the surface of the brain, while the whole brain and spinal cord is bathed in a cushion of liquid called the cerebrospinal fluid (CSF). The blood-brain barrier prevents many toxins from reaching the brain, but it can also make it difficult to deliver helpful treatments such as chemotherapy.
Each region of the brain is responsible for different critical functions. The cerebrum, consisting of a left and a right half at the front of the brain, controls voluntary movement, hearing, sight, personality, problem solving, learning and reasoning. The corpus callosum connects the two halves and relays information between them. The cerebellum, towards the back of the brain, coordinates fine motor skills and balance. The brain stem controls involuntary functions, such as breathing, swallowing, blood pressure and heart rate.
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