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The Brain

The brain controls the central nervous system, regulating breathing, heart rate, and digestion, as well as thinking and reasoning. For most animals, the brain is located in the head. However, some invertebrates (critters without a backbone, like insects) may not have a centralized brain, preferring to rely on collections of ganglia. Brains are very complicated collections of neurons Ð over a hundred billion of them!

Early peoples saw the brain as ÒstuffingÓ. Ancient Egyptians removed it during embalming Ð for them, the heart was the home of intelligence. We know better now, though traces of the old belief remain in sayings like, ÒI learned it by heart.Ó

The brain controls many systems. Without our knowledge, it regulates the autonomic nervous system, regulating breathing, heart rate, digestions, blood pressure, and body temperature. The brain is the source of all learning, emotion, and cognition. The brain looks after most functions of our body.

Brains are divided into grey matter and white matter. Grey matter refers to the cell bodies of neurons Ð they make up the outer layers of the brain, called the cortex. White matter refers to the axons, fibers that connect neurons to each other. These axons are covered by a sheath of myelin.

Neuroscience is the study of the brain. It tries to study the biology and physiology of the brain.

For insects, the brain is made of four parts. It collects sensory information from the insectÕs antenna and more, then translates that information into information that insects can understand. Other species have brains of different shapes.

For humans, the brain is divided into sections. The cerebrum is the grey, wrinkly outer layer. Underlying the cerebrum is the cerebellum, the white matter. Humans exhibit encephalization, the result of the larger brains we have gained over evolutionary history. This is most obvious around the part of the brain known as the neocortex, which is larger in humans than in any other animal.

Neurons convey information between cells. The brain also contains clial cells which support the neurons, clean up neorotransmitters, and manage waste.

The meninges are membranes that separate the brain from the skull. These three layers form a blood-brain barrier, which effectively keeps most toxins from entering the brain.

Cerebrospinal fluid bathes the brain, helping it to ÒfloatÓ within the skull Ð without this fluid, the brain would collapse under its own weight. This fluid also acts as a shock absorber, preventing damage to the brain.

The brain coordinates signals from various parts of the body, allowing us to breathe, move, and function. Upon death, all brain function stops (known as Òbrain deathÓ). Once this happens, the brain is no longer able to regulate breathing, heart rate, and even motion. Life ceases.

A sketch of the human brain by artist Priyan Weerappuli superimposed upon the profile of Michelangelo's David.

Comparison of the brain sizes of various species.

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