X-Message-Number: 3869 Date: Sat, 18 Feb 1995 21:42:20 -0800 From: John K Clark <> Subject: SCI.CRYONICS Uploading -----BEGIN PGP SIGNED MESSAGE----- I Wrote: >>there not signals unless they convey information. (Joseph J. Strout) Wrote: >And they do! [...] Synapses (chemical or electric) cause a >change in the voltage of the membrane of the postsynaptic cell >-- *locally* -- and this voltage change spreads >electrotonically over the cell. [...] These electrical signals >are crucial to the function of the cell, and act >at lightspeed over fairly large (on a cellular scale) distances. In the spine the axon on a neuron can be almost 3 feet long, the biggest cell in the body. Are you saying a nerve signal travels those 3 feet at the speed of light, or are you saying nothing can send a signal over those 3 feet faster than 300 miles per hour, the top speed a neuron is capable of? It really doesn't matter because both statements are untrue. Just because something uses voltage doesn't mean it can send messages at light speed. A constant voltage can generate a static electric field but a static field of any kind can't convey information, you need to vary the voltage , also voltage doesn't move through things it exists between things. Current (amps) is what moves through things. In electronics, current is caused by the movement of light fast electrons. In the brain current is caused by the movement of charged sodium and potassium atoms tens of thousands of times heavier than electrons and slow as a result. These heavy ions move in and out of the cell through gates made of protein. The movement of these ions causes a change of voltage across the cell membrane. The action potential is just a wave of voltage changes that travels down the axon. This wave of voltage changes, and not the voltage itself, is what contains information and it moves at less that the speed of light, a lot less. Helmholtz measured this speed long ago in 1852 in an experiment he didn't expect to work. He thought nerves were probably too fast for him to measure but to his surprise he found that only a few axons could send singles as fast as 100 meters per second and that unmyelinated axon's were only able to go about 1 meter per second. I remind you that light moves at 300,000,000 meters per second. John K Clark -----BEGIN PGP SIGNATURE----- Version: 2.6.i iQCzAgUBL0bUZH03wfSpid95AQHURATtEgBD0dBx6KFNyMfK3dwcQ/ZGk+tp64BK wptMroAOPEIrs2A80A0T/uaBD8/QdYcNDI5P5VCppWIjIQnjBYULeNQxZi5PMPii vycTQKhtyf8Yh/AFdJx+IUL5IQ3ogJxbEcD9haoUWlDiPHMTTdlzsekUy4YqF1IQ 1uaeDXN5cQwPCu+J8moxLWI+1K4A37Grc50S+9BQhd2zmWp8ghw= =LXmk -----END PGP SIGNATURE----- Rate This Message: http://www.cryonet.org/cgi-bin/rate.cgi?msg=3869