The squid giant axon is the very large (up to 1 mm in diameter; typically around 0.5 mm) axon that controls part of the Atlantic squid's (Loligo pealei) water jet propulsion system. Squid use this system primarily for making brief but very fast movements through the water usually when escaping predators. Between the tentacles of a squid is a siphon through which water can be rapidly expelled by the fast contractions of the body wall muscles of the animal. This contraction is initiated by action potentials in the giant axon. Action potentials travel faster in a larger axon than a smaller one, and squid have evolved the giant axon to improve the speed of their escape response. This has obvious adaptive advantage when escaping from predators. An axon, or nerve fiber, is a long slender projection of a nerve cell, or neuron, that conducts electrical impulses away from the neurons cell body or soma. ... Genera Loligo Loliolus Lolliguncula Pickfordiateuthis Sepioteuthis Uroteuthis Species Genus Loligo Veined Squid, Loligo forbesii Siboga Squid, Loligo pickfordi Loligo vietnamensis Spear Squid, Loligo (Undetermined) bleekeri Patagonian Squid, Loligo (Undetermined) gahi Bigeye Inshore Squid, Loligo (Undetermined) ocula Opalescent Inshore Squid, Loligo (Undetermined) opalescens Longfin Inshore Squid, Loligo (Undetermined) pealeii Slender Inshore... A. A schematic view of an idealized action potential illustrates its various phases as the action potential passes a point on a cell membrane. ... Escape response, escape reaction, or escape behaviour is a possible reaction in response to stimuli indicative of danger, in particular, it initiates an escape motion of an animal. ...

In their Nobel Prize-winning work uncovering ionic mechanism of action potentials, Alan Hodgkin and Andrew Huxley performed experiments on the squid giant axon. The large diameter of the axon provided a great experimental advantage for Hodgkin and Huxley as it allowed them to insert voltage clamp electrodes inside the lumen of the axon. To this day, no experimental preparation yields greater accuracy in the measurement of action potential characteristics, and is still widely used in their study. Sir Edward Appletons medal Photographs of Nobel Prize Medals. ... Sir Alan Lloyd Hodgkin (February 5, 1914 – December 20, 1998) was a British physiologist and biophysicist, who won the 1963 Nobel Prize in Physiology or Medicine for his work with Andrew Fielding Huxley on the basis of nerve action potentials, the electrical impulses that enable the activity of an organism... Andrew Huxley at Trinity College, Cambridge, July 2005 Family tree Sir Andrew Fielding Huxley, OM, FRS (born 22 November 1917, Hampstead, London, England, UK) is a British physiologist and biophysicist, who won the 1963 Nobel Prize in Physiology or Medicine for his work with Alan Lloyd Hodgkin on the basis... Electrophysiology is the study of the electrical properties of biological cells and tissues. ...

In an ironic twist of fate, at least in the waters around Plymouth, England and Woods Hole, Massachusetts, the top predator of the squid became scientists intent on dissecting their predator escape mechanisms. The Marine Biological Laboratory (MBL) is a famous scientific institution located in Woods Hole, Massachusetts. ...

See also

• Lateral giant neuron

The lateral giant neuron (LG) is an interneuron in the abdominal nerve cord of crayfish. ...

External links

• http://www.mbl.edu/publications/Loligo/squid/axon.large.jpg
• http://www.mbl.edu/publications/Loligo/squid/neuro1.html
• http://www.cephschool.utmb.edu/imgdb/thumbnails/TCB1541.jpg