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| title | chunk | source | category | tags | date_saved | instance |
|---|---|---|---|---|---|---|
| Alan Hodgkin | 2/4 | https://en.wikipedia.org/wiki/Alan_Hodgkin | reference | science, encyclopedia | 2026-05-05T16:53:40.084889+00:00 | kb-cron |
Hodgkin started conducting experiments on how electrical activity is transmitted in the sciatic nerve of frogs in July 1934. He found that a nerve impulse arriving at a cold or compression block, can decrease the electrical threshold beyond the block, suggesting that the impulse produces a spread of an electrotonic potential in the nerve beyond the block. In 1936, Hodgkin was invited by Herbert Gasser, then director of the Rockefeller Institute in New York City, to work in his laboratory during 1937–38. There he met Rafael Lorente de Nó and Kenneth Stewart Cole with whom he ended up publishing a paper. During that year he also spent time at the Woods Hole Marine Biological Laboratory where he was introduced to the squid giant axon, which ended up being the model system with which he conducted most of the research that eventually led to his Nobel Prize. In the spring of 1938, he visited Joseph Erlanger at Washington University in St. Louis who told him he would take Hodgkin's local circuit theory of nerve impulse propagation seriously if he could show that altering the resistance of the fluid outside a nerve fibre made a difference to the velocity of nerve impulse conduction. Working with single nerve fibres from shore crabs and squids, he showed that the conduction rate was much faster in seawater than in oil, providing strong evidence for the local circuit theory. After his return to Cambridge he started collaborating with Andrew Huxley who had entered Trinity as a freshman in 1935, three years after Hodgkin. With a £300 equipment grant from the Rockefeller Foundation, Hodgkin managed to set up a similar physiology setup to the one he had worked with at the Rockefeller Institute. He moved all his equipment to the Plymouth Marine Laboratory in July 1939. There, he and Huxley managed to insert a fine cannula into the giant axon of squids and record action potentials from inside the nerve fibre. They sent a short note of their success to Nature just before the outbreak of World War II.
== Wartime activities == Despite his Quaker upbringing, Hodgkin was eager to join the war effort as contact with the Nazis during his stay in Germany in 1932 had removed all his pacifist beliefs. His first post was at the Royal Aircraft Establishment where he worked on issues in aviation medicine, such as oxygen supply for pilots at high altitudes and the decompression sickness caused by nitrogen bubbles coming out of the blood. In February 1940 he transferred to the Telecommunications Research Establishment (TRE) where he worked on the development of centimetric radar, including the design of the village Inn AGLT airborne gun-laying system. He was a member of E.G. Bowen's group in St Athan in South Wales and lived in a local guest house together with John Pringle and Robert Hanbury Brown. The group moved to Swanage in May 1940 where Pringle replaced Bowen as leader of the group. In March 1941, Hodgkin flew on the test flight of a Bristol Blenheim fitted with the first airborne centimetric radar system. In February and March 1944, he visited the MIT Radiation Laboratory to help foster the interchange of information on developments in radar between Britain and America. Providing a readable account of the little-known piece of military history that he was a part of during World War II was a main motivation for Hodgkin to write his autobiography Chance and Design: Reminiscences of Science in Peace and War.
== 1945–1963: Action potential theory and Nobel Prize ==
As the Allied Forces' invasion of France and their continued advance towards Germany in autumn 1944 suggested an end of the war in the foreseeable future, Hodgkin started to plan his return to a career in research at Cambridge. He renewed his collaboration with W. A. H. Rushton and they published an article on how to calculate a nerve fibre's membrane resistance, membrane capacity, its axoplasm's resistance, and the resistance of the external fluid in which the fibre is placed, from experimental observations. After being released from military service in August 1945 upon Adrian's request, Hodgkin was able to restart his experiments in collaboration with Bernard Katz and his pre-war collaborator Andrew Huxley. They spent the summers of 1947, 1948, and 1949 at the Plymouth Marine Laboratory where they continued to measure resting and action potentials from inside the giant axon of the squid. Together with Katz, he provided evidence that the permeability of the neuronal cell membrane for sodium increased during an action potential, thus allowing sodium ions to diffuse inward. The data they had obtained in 1949 resulted in a series of five papers published in The Journal of Physiology that described what became later known as the Hodgkin–Huxley model of the action potential and eventually earned Hodgkin and Huxley the Nobel Prize in Physiology or Medicine. Building on work by Kenneth S. Cole they used a technique of electrophysiology, known as the voltage clamp to measure ionic currents through the membranes of squid axons while holding the membrane voltage at a set level. They proposed that the characteristic shape of the action potential is caused by changes in the selective permeability of the membrane for different ions, specifically sodium, potassium, and chloride. A model that relies on a set of differential equations and describes each component of an excitable cell as an electrical element was in good agreement with their empirical measurements.