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 ↓
Signals refresh along bare membrane. Fatty myelin covers stretches; only the exposed gaps, or nodes, refresh. Each refresh takes time.
Wider fibers let current spread more easily, all else equal.
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.
