Re: The speed of nerves

[Guest guest]

Yes, nerves have " huge " propagation delays compared to

electronics 100 ft/sec verses 186000 mi/sec... that's because

nerves pass signals from one neuron to the next by releasing a chemical

that defuses across the gap between the fibers...

It causes some interesting paradoxes... to jump off a building taller

than about 10 stories is a " painless " way to die... because by

the time the nerve impulse travelled from the point of impact to your

brain, your brain would already be splattered on the ground... no brain

to interpret the impulse therefore no pain...

Ender

At 05:17 PM 8/22/2006, you wrote:

RE Speed of neural transmission.

The speed of transmission in ~sensory~ nerves was evaluated by Hirsch at

about 34 m/s.

From:

http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve & db=PubMed & list_uids=9084235 & dopt=Abstract

Trying to put that on, what is to me, more of an intuitive scaling-

34m/s times (about) 3 feet per meter times (?) 5240 feet per

mile times 60 seconds per minute times 60 minutes per hour... doing rough

mental computations I get 102 f/s, 360000 feet per hour, or roughly 70

miles per hour.

... or perhaps anyway the meters per second is most intuitive if

you look at it from the perspective of how long it takes retinal patterns

to travel down through the optic chiasma at the base of the brain back to

the occipital lobe visual processing areas and then eventually back up to

guide the direction of eye gaze at the person whose reflexes are

amazingly fast. And maybe it's best to think of a series of informational

feedback loops through the brain from retina through to eye-direction to

track the movement of the person... I'm thinking in images of movie film

stills on a reel here... If there are say twelve stills to

" effectively " eye-track a person's movement, then ten times the

length of the path through the brain informational loop of say 1/4

meter... (I just love that duodecimal number system!...) Then 12/4 = 3

meters. Then since sensory nerve transmission (per the text linked above)

is 34 m/s, and the signal is travelling 3 meters, it's about 1/9th of a

second. I probably made a mistake somewhere, but intuitively that sounds

ballparkish to me at the moment. Also, a huge simplification here- it's

sensory nerve signal tansmission that travels at 34 m/s. Other signals,

travelling through the brain, tend to be quite a bit slower I seem to

recall.

Summarizing...The hand is quicker than the brain?

Heph

environmental1st2003 <no_reply >

wrote:

It's the same with me. But whenever I move that fast, I scare

people.

Usually what will happen is that someone will drop something and

then I will reach for it and catch it. I usually do this so fast my

hand is a blur. It's the same thing if i try to catch a fly or

insect that is flying around.

I can also turn 180 degrees on my feet as quick as lightning if I

have to.

Tom

Administrator

Even though I usually move like most people, my reactions can be

very quickly. In fact, there have been a few cases where I move so

quickly, like in a lunge or a strike from close range, that it was

faster than people could really follow with their eyes.