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Baby Astronaut

Brain signals travel at lightspeed?

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Do the electric impulses in the body travel at the speed of light? For example, if something brushes your toe, or your eye detects a flying mosquito, does it sent the info to our brain at the speed of light?


I'm not asking how fast the brain processes the info, just how quickly it's reached by the signals.

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Nope. Not even close. Roughly 100 m/s is the max (whereas light travels at ~300,000,000 m/s).



This page covers it pretty well:


Action potentials can travel along axons at speeds of 0.1-100 m/s. This means that nerve impulses can get from one part of a body to another in a few milliseconds, which allows for fast responses to stimuli. (Impulses are much slower than electrical currents in wires, which travel at close to the speed of light, 3x108 m/s.) The speed is affected by 3 factors:


  • Temperature - The higher the temperature, the faster the speed. So homoeothermic (warm-blooded) animals have faster responses than poikilothermic (cold-blooded) ones.


  • Axon diameter - The larger the diameter, the faster the speed. So marine invertebrates, who live at temperatures close to 0°C, have developed thick axons to speed up their responses. This explains why squid have their giant axons.


  • Myelin sheath - Only vertebrates have a myelin sheath surrounding their neurones. The voltage-gated ion channels are found only at the nodes of Ranvier, and between the nodes the myelin sheath acts as a good electrical insulator. The action potential can therefore jump large distances from node to node (1mm), a process that is called saltatory propagation. This increases the speed of propagation dramatically, so while nerve impulses in unmyelinated neurones have a maximum speed of around 1 m/s, in myelinated neurones they travel at 100 m/s.

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