Under your skin, tiny alarm endings notice a hard bump or scrape. Tap the knee patch to start one message.
tap the skin
toward the spinal cord ↓
Some fibers wear short sections of fatty myelin. Between the covers are tiny exposed gaps called nodes.
myelin cover
exposed node
The cover is not one solid tube. The exposed nodes stay part of the living axon membrane.
Drive one sample message. Under a covered stretch, current spreads ahead. At the next exposed node, the full signal is refreshed.
message ready at the first node
One fiber · no comparison · no finish time
Now meet Maya's two pain fibers. They are naturally different fibers—not one fiber with its coat removed.
SAME KNEE STARTSAME SHOWN DISTANCE
ALIGHT WRAP · A LITTLE WIDER
BNO MYELIN · FINER
A: lightly wrappedB: unwrappedboth start together
Same knee start · same shown distance · two naturally different fibers
Two pain signals start together at Maya's knee. Which signal reaches the nervous-system bell first?
Slide the race from the bump to both arrivals.
KNEENERVOUS-SYSTEM BELL
A
B
Move slowly enough to compare both gold dots.
