How We Live and Why We Die by Lewis Wolpert

Author:Lewis Wolpert [Lewis Wolpert]
Language: eng
Format: epub
ISBN: 9780571250851
Publisher: Faber & Faber
Published: 2009-04-07T04:00:00+00:00

9

How We Move, Think and Feel

how nerve cells communicate

The grey, soft, lumpy mass that is the human brain is rightly regarded as probably the most complex structure in the universe. There are some 100 billion nerve cells, also known as neurons, in our brains, and even more supporting cells, and that this mass of cells does all our thinking and feeling is almost beyond belief. Everything we do is determined by this impossibly complex society of nerve cells. But exactly how they communicate in their complex networks so we can think and feel, and be conscious of what we are doing, and can walk, if we wish, in a straight line while having creative thoughts at the same time, is a puzzle.

It is all due to signalling between the nerve cells. Long extensions from nerve cells are often bound together in a common cable-like bundle – this is what is commonly called a nerve and can be very long. In addition to nerve cells there are even more numerous supporting cells in our brains known as glia. Their function is not to signal but to provide insulation, support, removal of debris, and also to nourish nerve cells.

Nerve cells both communicate with other nerve cells in the brain and also send out signals via long nerves that cause muscles to contract. One of the main functions of our brain, and its evolutionary origin, is to control the contraction of muscles, and so how we move. Given the complexity of the connections in the brain, how is this set up during its development? A nice question is the extent to which different nerve cells have unique identities that are specified during embryonic development. In fact different combinations of just 37 genes could, in principle, specify every one of the billions of cells in the brain. But how this enormous society of brain cells talking to each other can give rise to all our thoughts, emotions, movements and even consciousness still remains a mystery.

Nerve cells have the prime duty to carry messages rapidly to other cells, mainly to other nerve cells but also to muscle. Just as important are those nerves that carry information from different parts of the body to the brain, and which are the basis of how we sense what is going on around us. There are nerves involved in our sense of touch, nerves that enable us to feel pain and thus try to remove the cause, nerves in our eye that carry the information that enables us to see, and nerves for detecting smells and the local temperature. All these transfers of messages involve an ingenious way of sending a message along the nerve cell based on changes in the electrical charge across the cell membrane.

Every nerve cell has a small region similar in size to most other cells containing the nucleus with the genes and mitochondria; this is where protein synthesis takes place, and from this region there are long, thin extensions. Usually there is one particularly

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