Mechanism and Drawback of Super-high Conduction Velocity of Shrimp Giant Nerve
Asia-Pacific Journal of Biology
Volume 1, Issue 1, December 2018, Pages: 11-15
Received: Nov. 8, 2018; Accepted: Dec. 12, 2018; Published: Feb. 20, 2019
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Fan Shihfang, Former Shanghai Institute of Physiology, Academia Sinica, Shanghai, China
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1. The conduction velocity of action potential of shrimp (Penaeus) giant nerve is very high, may reach 200-300m/sec. So far, besides shrimp, the highest conduction velocity known is the Aαfiber of mammals -~120m/sec. 2. Super-high conduction velocity of shrimp giant nerve is due to its particular structures and electrophysiological properties: (a) large diameter of the nerve, may reach 200µ; (b) thick myelin sheath, may reach 50µ; (c) small axon diameter, only about 10µ or so, in turn, there is big gap between myelin sheath and axon; (d) the area of round shaped Ranvier node-like structure is small; (e) the internodal distance is long; (f) there is Donnan potential in the gap medium. With such structure and physiological properties, as one Ranvier node-like structure is excited, the local current counter acted by Donnan potential in the gap medium, could only run in the thin axon and passes through the small Ranvier node-like structure ahead. The current density through this Ranvier node-like structure will be high and the node will be excited rapidly. Thus, the action potential will go forward fast. b3. The huge space occupied by the giant nerve, together with the formation and maintenance of the thick myelin sheath not only consume appreciably amount of energy but also produce a lot of free radical. These factors prevent the development of such giant nerve in other animals in the course of evolution.
Shrimp Giant Nerve, Super-High Conduction Velocity, Submyelin Space
To cite this article
Fan Shihfang, Mechanism and Drawback of Super-high Conduction Velocity of Shrimp Giant Nerve, Asia-Pacific Journal of Biology. Vol. 1, No. 1, 2018, pp. 11-15.
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