Do nerve endings closer to the brain / spinal cord take less time to transmit signals because there is less distance to travel?

Submitted by ssinatra3 t3_zzgd7y in askscience

On a related note, do different nerves or nerve endings have greatly different reaction times or time taken to transmit signals irrespective of the distance the signal must travel back to the brain / spinal cord? Is sensitivity of any kind (olfatory, visual, tactile) a measurable paramter between different humans? What affects the magnitude of sensory input required for a person to detect a new stimulus?

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matticitt t1_j2cej5s wrote

Yes, it takes longer for information from your toe for example to reach your brain that information from your eye. Your brain actually synchronizes all those inputs and so there's a delay for you and the information which got to your brain first has to "wait" to get synced with the one which got there last. You're always living slightly in the past.

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neuralbeans t1_j2ciyir wrote

How do they get synchronised? Is it just a matter of there being discrete time steps when the signals get processed? Do the time steps get longer as you grow taller in order to accommodate the longest nerves?

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thisoldmould t1_j2ceo3p wrote

This depends on the sensation being transmitted to the brain. Some nerves travel at hundreds of metres per second (A-delta fibres), others travel at only 2 m/s (C-fibres).

The distance to the brain will impact the time taken for the sensation to be delivered to the brain. But it’s usually imperceptible because the signals are so quick.

Nociception (noxious stimulus) carried by C-fibres, are integrated in the thalamus and modulated by pro and anti-nociceptive areas of the brain, which can delay your perception of pain.

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neuralbeans t1_j2cj8xp wrote

Is delayed pain perception a problem for very tall people such as those with giganticism?

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mckulty t1_j2cwzi8 wrote

The difference between nerves that carry light touch and nerves that carry deep pain is pretty big. Remember stubbing your toe and waiting for the pain to arrive?

The difference between a short person and a tall person is not as big as that.

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keithatcpt t1_j2eshe2 wrote

Robert Wadlow (tallest man ever) died from an infection on his foot when he couldn’t feel a brace cutting into his skin.

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MrsMurphysChowder t1_j2fjj87 wrote

This is why when you whack your shin, rubbing the skin dulls the pain. It is also why mentholated muscle rubs, and TENS units work.

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Xyver t1_j2ce9ur wrote

Semi related answer, yes I know there is a noticable time delay for sending signals for the brain to your feet/hands, something in the range of 50-100ms. I assume that since it's an actual electrical signal travelling through the nerves, further things take longer.

But the exciting thing is, that is way slower than the speed of a signal through a wire. So for someone with a prosthetic leg, if you get the signals from the brain stem and send them through wires (or other digital means) to muscles/actuators in a robot leg, you would make faster reflexes and response times.

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Danzevl t1_j2cxzs6 wrote

The problem I see there is making an effective organometallic interface or flexible carbon wire that can also send signals back to make it function seamlessly.

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Malalang t1_j2chcvu wrote

So, let's say traveling at 100 km per hour, you would travel 1 meter less if brakes could be applied by hand instead of by foot?

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