All in all, we have about 90,000 miles of neurons

All in all, we have about 90,000 miles of neurons in our central nervous system. You could circle the earth more than three times, if you laid all your nerves end-to-end. Obviously, not every single neuron in the body is used to transmit one signal to the spinal cord and/or brain, so no impulse will ever travel all that way. But even our “closest” encounters involve distance, as the sensory information needs to travel from where it gets picked up, to where your body/brain decides what to do about it.

Nerves in your skin pick up the sensation of a snow flurry landing on your forearm, the sense data are transmitted along neurons leading to your spinal column. That kicks off a reaction that tells your hand to brush off the tiny dot of water – almost before you’re even aware of it. You don’t even need to stop and think about it. Your nervous system handles it for you.

Meanwhile other impulses travel all the spinal cord up to your brain, where it will decode the experience and you (may) become aware of it. The incredibly intricate network passes those signals from one neuron to another, from axon (the neurons’ “transmitter”) to dendrite (the neurons’ “receiver”) to the cell body, and on to the next axon(s) and dendrite(s) in the chain, some of those signals moving at the rate of 200+ miles per hour. Irritation, surprise, and maybe a little anxiety makes an appearance. Your immediate shake-it-off reflex is followed by conscious thought. Is it going to really start snowing? Is there enough time to empty the truck? Is Great-Grandpa’s antique leather satchel going to be damaged by moisture? And so it goes, as our environment inundates us with inputs and stimuli and prompts, every living moment of our lives. We have to keep up. Our senses have to stay on top of things, regardless of whether we’re paying close attention or not. But then, that’s what our nervous system is particularly good at. And it does it so well, we don’t even realize how much it takes to get the job done.

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