Elwood Henneman (1915 – 22 February 1996) was an American neurophysiologist who studied the properties of vertebrate motor neurons.

Biography and Research

Henneman received his bachelor's degree from

Harvard College Harvard College is the undergraduate college of Harvard University, an Ivy League research university in Cambridge, Massachusetts. Founded in 1636, Harvard College is the original school of Harvard University, the oldest institution of higher lea ...

in Cambridge, Massachusetts in 1937. In 1943 he finished his medical studies at

McGill University McGill University (french: link=no, Université McGill) is an English-language public research university located in Montreal, Quebec Montreal ( ; officially Montréal, ) is the second-most populous city in Canada and most populous ...

in Montreal. During a research fellowship at

Johns Hopkins University Johns Hopkins University (Johns Hopkins, Hopkins, or JHU) is a private research university in Baltimore, Maryland. Founded in 1876, Johns Hopkins is the oldest research university in the United States and in the western hemisphere. It consi ...

in Baltimore, Maryland, Henneman and colleague,

Vernon Mountcastle Vernon Benjamin Mountcastle (July 15, 1918 – January 11, 2015) was an American neurophysiologist and Professor Emeritus of Neuroscience at Johns Hopkins University. He discovered and characterized the columnar organization of the cerebral co ...

, showed that tactile information about the extremities is represented in an orderly map in the ventrolateral

thalamus The thalamus (from Greek θάλαμος, "chamber") is a large mass of gray matter located in the dorsal part of the diencephalon (a division of the forebrain). Nerve fibers project out of the thalamus to the cerebral cortex in all directions, ...

of the cat and monkey. Further research positions followed, including at the Royal Victorian Hospital and at the Illinois Neuropsychiatric Institute (NPI) in Chicago. At NPI, Henneman discovered that the drug

Mephenesin Mephenesin ( INN) is a centrally acting muscle relaxant. It can be used as an antidote for strychnine poisoning. Mephenesin however presents with the major drawbacks of having a short duration of action and a much greater effect on the spinal co ...

(Myensin) inhibits interneurons in the spinal cord and thus causes muscle relaxation. This discovery helped lead to the development of muscle relaxant drugs. Of greater impact for the scientific community was Henneman's work describing the physiology of

motor neurons A motor neuron (or motoneuron or efferent neuron) is a neuron whose cell body is located in the motor cortex, brainstem or the spinal cord, and whose axon (fiber) projects to the spinal cord or outside of the spinal cord to directly or indirectly ...

, the neurons that control contraction of the muscles. In 1957, Henneman published experimental results that showed that motor neurons that project to the same muscle are recruited on the basis of their size.

Henneman's Size Principle Henneman’s size principle describes relationships between properties of motor neurons and the muscle fibers they innervate and thus control, which together are called motor units. Motor neurons with large cell bodies tend to innervate fast-twi ...

describes this relationship. In 1971, Henneman became chair of the Department of Physiology at Harvard Medical School, a position he held until his retirement in 1984.

Awards and honors

In 1997, Henneman was posthumously elected to the American Academy of Arts and Sciences.

Death

Elwood Henneman passed away in 1996 at age 80, of heart failure.

Literature

Hans Peter Clamann: Elwood Henneman and the Size Principle. Journal of the history of the neurosciences. Vol. 11, no. 4 (Dec. 2002) p. 420–421.

References

{{DEFAULTSORT:Henneman, Elwood American neuroscientists 1915 births 1996 deaths McGill University Faculty of Medicine alumni Harvard College alumni