Sir Andrew Huxley was one of the leading scientists of his era. An outstanding physiologist and biophysicist he, and his long-time collaborator Sir Alan Hodgkin (and the Australian biophysicist Sir John Eccles), won the 1963 Nobel Prize in Physiology or Medicine for his studies of nerve action potentials, the electrical pulses that enable the activity of an organism to be co-ordinated by a central nervous system.
The nerve cells communicate with each other and give orders to muscles and glands in the body by brief electrical pulses — the pulse in a nerve fibre lasts for about a thousandth of a second.
The methods used by Huxley and Hodgkin were based on electronics. They recorded the electrical processes with microelectrodes, amplified them about a million times, and then displayed them on the screen of a cathode ray tube. Their research led them to hypothesise the existence of channels in the membranes of nerve cells through which ions pass. These were duly isolated, but only decades later.
The research of Huxley and Hodgkin was based on work they did with the so-called giant axon — or nerve fibre — of the Atlantic squid, a creature indirectly responsible for much of what we know about how neurons work. An axon, which is a single cell, is a long projection of a nerve cell, or neuron, that conducts electrical impulses away from the body of the neuron cell body. As such they are the primary lines of transmission of the nervous system. Bundles of them help make up nerves.
An axon has a very small diameter — typically about one micrometre (a millionth of a metre) — but, relatively, it may be extremely long. The axons that make up the sciatic nerve in the human body, for example, run from the base of the spine to the big toe of each foot, so they may be more than a metre in length.
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The physiology of axons has been studied a great deal. The work of Huxley and Hodgkin on giant axons of the squid led to the formulation of the Hodgkin-Huxley Model. This giant axon extends from the head to the tail of the squid and is used to move the squid’s tail. They chose it because it has the largest diameter of the invertebrate axons, sufficiently large for them to be able to insert an electrode into the axon.
Neurons send messages electrochemically, using chemicals to produce an electrical signal. Chemicals in the body are normally electrically charged (they are ions). In the nervous system, the important ions are calcium, potassium, sodium, and chloride. Nerve cells are enclosed in a membrane that allows some ions to pass but blocks the passage of others.
Huxley and Hodgkin studied action potentials. An action potential occurs when a neuron sends information down an axon, away from the cell body. It is caused by an exchange of ions, mainly sodium and potassium ions, across the neuron membrane. Using the squid axon they were able to record ionic currents.
Their research enabled them to describe the conduction of a nerve impulse in quantitative terms and to make successful predictions about the shape and velocity of the nerve impulse on the basis of electric currents generated by a movement of sodium ions into the nerve fibre followed by an outward movement of a similar quantity of potassium ions.
These ionic movements depend on increases in the permeability of the cell membranes that are brought about by changes in the electrical potential across the membrane. The immediate source of energy for the conduction of nerve impulses is the movement of sodium and potassium down their concentration differences, which are built up and maintained by relatively slow biochemical processes.
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Huxley and Hodgkin published their theory in 1952. In their paper they describe one of the earliest computational models used in biochemistry; it was the basis of most of the models used in neurobiology for the ensuing 40 years.
In addition to his work on nerve cells, Huxley made outstanding contributions to our knowledge of muscular contraction. In experiments with isolated muscle fibres he showed that contraction was accompanied by a shortening of one part of the muscles striation (band) pattern — the isotropic band — while the remaining part, the anisotropic band, remained constant.
The results of his research led him, with H. E. Huxley (no relation), to propose a “sliding filament” mechanism as the basis of muscular contraction. This hypothesis was one of the great biological advances of the 20th century.
During further microscopic observations on single muscle fibres, Huxley and his colleagues produced striking evidence about the way in which electrical changes of the cell membrane are communicated through local tubular channels to the interior of the muscle fibre where they activate the contractile elements.
In later work Huxley continued to develop the single-fibre technique, using new methods to resolve the fine details of the dynamic changes that occur during muscular contraction.
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Andrew Fielding Huxley was born in Hampstead, London, in 1917, into a remarkable family. His father, Leonard Huxley, was a son of the scientist and writer Thomas Huxley, an early champion of Charles Darwin’s ideas about evolution, nicknamed “Darwin’s bulldog” for his pains. Sir Julian Huxley, the biologist, and Aldous Huxley, the writer, were Andrew’s stepbrothers.
Between 1925 and 1930 he was educated at University College School, London and between 1930 and 1935 at Westminster School, London. In 1935 he went to Trinity College, Cambridge having won a scholarship. He took physics, chemistry, physiology and mathematics in Part I of his degree at Cambridge and decided to specialise in physiology in Part II.
In August 1939 he wanted to get some experience in research methods and went to work with Hodgkin at the Marine Biological Laboratory at Plymouth. They succeeded in recording electrically from the inside of the squid giant axon.
During the first year of the Second World War, Huxley was a medical student, but medical teaching in London was stopped by air raids and he spent the rest of the war on operational research in gunnery, first for AntiAircraft Command and later for the Admiralty.
In 1941 Huxley was elected to a research fellowship at Trinity College, Cambridge, and he took this up at the beginning of 1946. He was also given a teaching appointment in the Department of Physiology at Cambridge. He held college and university posts in Cambridge until 1960 when he was appointed head of the Department of Physiology at University College London.
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In 1969 he took up a Royal Society Research Professorship at the Department of Physiology at University College London. He became Emeritus Professor in 1983. Between 1946 and 1951 Huxley worked mostly with Hodgkin on nerve conduction. In 1952 he turned to muscle contraction, and that continued to be his main line of work. He worked at Woods Hole, Massachusetts in 1953 as a Lalor Scholar; gave the Herter Lectures at Johns Hopkins Medical School in 1959; and the Jesup Lectures at Columbia University in 1964.
He was elected a member of the Royal Society of London in March 1955 and was knighted in November 1974. He was appointed to the Order of Merit in 1983.
From 1980 to 1985 he served as president of the Royal Society, earning wide respect for his ability to be simultaneously diplomatic, lucid and forthright in defence of scientific education and research. Between 1984 and 1990 he was master of Trinity College, Cambridge, succeeding his friend Alan Hodgkin. Huxley remained a Fellow at Trinity College, Cambridge, teaching in physiology, natural sciences, and medicine, for most of his life.
Huxley’s wife, Richenda, whom he married in 1947, predeceased him in 2003, and he is survived by their son and five daughters.
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Professor Sir Andrew Huxley, OM, FRS, physiologist and biophysicist, was born on November 22, 1917. He died on May 30, 2012, aged 94