He was in his early 20s when he began his research on the electrical and chemical processes that control the actions of muscles. He teamed with Alan L. Hodgkin, a fellow scholar at Trinity College, and began conducting experiments on nerve tissue from a squid.
After World War II, when both scientists were recruited to help with projects for the British war effort, they resumed their research on nerve impulses. They studied the squid because its axons, or nerve fibers, are much larger than those of other animals — and hundreds of times larger than human neurons.
They inserted electrodes into the nerve cells and measured the electrical currents produced when the nerve was stimulated. Through years of painstaking work and exacting calculations, Mr. Huxley developed the mathematical equations that explained how the nerve impulses travel through muscle fiber.
After Hodgkin and Mr. Huxley published their findings in 1952, an Australian scientist, John C. Eccles, used their principles to describe how nerve impulses are transmitted across synapses to other cells. All three scientists were awarded the Nobel Prize in Physiology or Medicine in 1963.
The research of Hodgkin and Mr. Huxley proved to be a major advance in biochemistry and neurobiology. It became the basis for later work by other scientists that has led to a fuller understanding of diseases of the nervous system and the functioning of the kidneys and heart.
Later in his career, Mr. Huxley turned to the study of muscle contraction. He designed a microscope to examine the striation pattern of muscle fibers and developed key mathematical equations to describe biochemical processes and other forces that cause muscles to contract. He continued to do research until his final years.
“Many things are still uncertain about the way in which a myosin molecule pulls on an actin filament to make a muscle contract,” he wrote in 2004, “and I still spend time thinking about this problem.”
Andrew Fielding Huxley was born Nov. 22, 1917, in the Hampstead section of London. He was the younger of two sons from his father’s second marriage. (His brother became a lawyer and settled in New York City.)
His father, Leonard Huxley, was a schoolmaster, writer and magazine editor who had four children from his first marriage, including Aldous Huxley, the author of “Brave New World” and other works, and Julian Huxley, an evolutionary biologist who was the first director general of UNESCO — the scientific and cultural arm of the United Nations — and a founder of the World Wildlife Fund.
Leonard Huxley published a two-volume biography of his own father, Thomas Henry Huxley. T.H. Huxley was a 19th-century scientist and writer who became known in the 1860s as “Darwin’s bulldog” for his forceful advocacy of Charles Darwin’s theory of evolution. He also coined the term “agnostic” to describe his religious beliefs — or lack thereof.
Andrew Huxley, who became interested in the study of physiology at Cambridge, noted in an autobiographical essay published in 2004 that his grandfather was deeply interested in the same subject a century earlier. T.H. Huxley had described physiology as “the mechanical engineering of living machines.”
Mr. Huxley received a bachelor’s degree from Cambridge in 1939 and was beginning medical studies when was called away during World War II to help develop antiaircraft weapons for the British military.
Mr. Huxley worked at Woods Hole, Mass., in 1953, and lectured at Johns Hopkins University medical school in 1959 and at Columbia University in 1964. He became head of the physiology department at University College London in 1960.
After being elected a fellow of the Royal Society in 1955, he served as president of the august British scientific organization from 1980 to 1985. In his 1981 presidential address, he took up the same themes his grandfather had championed, delivering a rousing defense of Darwin and his revolutionary ideas of evolution.
In 1947, Mr. Huxley married Jocelyn Pease, who died in 2003. Survivors include six children.
Mr. Huxley was knighted in 1974 and received the British Order of Merit in 1983. He returned to Cambridge to serve as master of Trinity College from 1984 to 1990.
He liked to point out that his college had produced more Nobel laureates than the entire nation of France.