CoachPuberty is not decided in the organs it changes. It is ordered — by chemical messengers called hormones: substances released into the blood by specialized organs, carried everywhere, and obeyed by the organs built to hear them. At puberty, a control center at the brain’s base wakes, its hormones instruct the reproductive organs, and their hormones — carried body-wide by Proposition 27.1’s delivery service — order the whole rebuild: growth, hair, voice, cycles.
Examples
Example 56.5 (One signal, many building sites)
The blood carries a hormone everywhere at once — which is why puberty is a coordinated rebuild: voice, shoulders and hair follow the same messenger, on one schedule, though the sites lie half a body apart. No nerve wiring connects a voice box to a beard; the bloodstream’s broadcast does (Chapter 61 makes this system a chapter of its own).