The human brain is the most complex organ in the human body. It is the control centre of life. It not only affects and governs everything you do, how you think, feel and act, but what kind of person you are.
There is much more about this mysterious organ which baffles doctors, scientists and philosophers.
Proportionate to body weight, humans have the largest brains among mammals. No animal brain approaches the human brain’s capacity for learning, language and thought. The human brain is far more superior to even the most sophisticated supercomputer ever designed.
The brain is far more complicated than anything ever made by humans even though it’s only about the size and shape of an oval grapefruit.
Weighing a mere 1.4 kilos (three pounds), the brain can consume up to a third of the body’s energy, depending on the demand you put upon it. At the same time, it demands the same proportion of the body’s blood supply. That is why a mentally challenging office job can be just as tiring as physical work. Think hard and you could lose weight!
The brain is very soft, rather like an infinitely wrinkled jelly. It consists of an amazing mass of 100 billion nerve cells, known as neurons, and there are one million billion connections between them, as well as to muscles and glands and other tissue.
Neurons vary greatly but share three major features. Each has a centre (nucleus), an axon which transmits nerve impulses electrochemically to other cells and branches (dendrites) which receive them.
The brain is shaped like two fists side by side on a single wrist. The ‘fists’ are the left and right hemispheres of the largest part of the brain, the forebrain, or cerebrum. The ‘wrist’ is the brainstem, which connects the brain to the spinal column. At the back of the brain, below the cerebrum, is the cerebellum.
Each hemisphere has an outer layer consisting of six layers of cells called the grey matter and known as the cerebral cortex. It is only millimetres thick but accounts for 40 percent of the entire brain mass because of the way the brain tissue is folded.
Beneath the cortex are tracts of nerve fibres forming the remaining 60 percent of the brain mass, this is known as the white matter. These tracts connect areas of the cortex to each other and to nerve centres in the centre of the forebrain and brainstem.
Although the cerebrum looks symmetrical, the two hemispheres differ in size, shape and function. The right hemisphere controls the left side of the body, and vice-versa. In most people, the left brain seems dominant in its control of language and logic, the right hemisphere in spatial perception, art, music and creative thought. The two hemispheres communicate via dense bundles of nerve fibres called the corpus callosum.
The brainstem controls functions that are essential for survival such as breathing, digestion, heart rate, blood pressure, arousal and alertness. The cerebellum helps coordinate movement, muscles, balance and posture. Both brain stem and cerebellum work by reflex action – no thinking is involved. They receive sensory information such as heat or cold, pressure or pain, from receptors all over the body and transmit the appropriate physical responses. So blinking and standing up, for example, don’t require conscious thought.
The human brain is formidably protected in three key ways. First, of course, is the skull. Secondly, the brain is encased in three layers of membranes, the meninges. Cerebrospinal fluid circulating within them both nourishes the brain and cushions it against sudden movements or blows to the head.
Thirdly, the so-called blood-brain barrier, a membrane that separates the brain tissue from the blood whilst letting needed substances and oxygen through, ensures a controlled, consistent environment for the brain.s
Like other organs, the brain does best if well nourished. Diets high in animal fats and low in fresh fruit and vegetables can lead to hardened arteries and strokes just as they can lead to heart attacks.
Exercise is important too. As with muscles, so with the brain: if you don’t use it, you may lose it. And, of course, it suffers if poisoned so it is important not to smoke.