CoachThe nervous system is the body’s command network:
- the brain, in the skull’s shelter (Definition 17.1), is the center: it receives all reports and issues all orders;
- the spinal cord, a thick cable of nerve tissue, runs from the brain down inside the spine’s protective column;
- the nerves, white threads branching from brain and spinal cord to every organ, carry the messages — at more than for the fastest.
Examples
Example 33.3 (The catch, replayed slowly)
Replay the half-second: eyes track the ball and report, continuously; the brain, comparing report after report, works out where the ball will be; orders stream out to legs (a step left), trunk (lean), arm and fingers (open — now close). No single organ “caught the ball”: eyes, brain and muscles each played their line of Proposition 33.2.
Example 33.10 (Helmets are for the loop)
Bones mend (Remark 17.3); the brain’s tissue, once badly hurt, mostly does not. That is the calculation behind bicycle helmets: skull plus foam where the body’s own protection might not be enough. Cheap insurance for the organ running everything else.