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A fielder ran for a high catch. Legs moved. Hands rose. Eyes tracked the ball. Nobody decided each step on its own.

Who told the legs? Who told the hands, at the same time?

What this track covers

This is Chapter 6, Control and Coordination. This chapter asks one question. What keeps a body's many parts working together?

One body, many parts — many parts, one body, all working together.
The message and the messenger — a fast signal, cell to cell.
The shortest path — a reflex acts without waiting for the brain.
The centre and the cable — the brain and spinal cord. They control the body.
Messages in the blood — a chemical message that reaches target cells.
Sugar and feedback — insulin and feedback keep blood sugar steady.
Checkpoint — six marked questions on the lessons so far.
Plants bend toward the light — a chemical makes a plant bend. Plants also respond to touch.
Other plant hormones — three more plant hormones, each with its own job.
Fast and slow, side by side — two systems, two speeds.

These earlier lessons help.

Four processes, one body (Life Processes, Class 10). The body does many jobs at once.
A cell that carries signals (Tissues in Action, Class 9). One tissue passes a message fast.
Chemical messages in the blood (Adolescence, Class 7). The blood carries chemical messages too.
A sign of being alive (Living Creatures, Class 6). Living things respond to their surroundings.

Every bench here is a simulation. It says so on its own screen. No bench measures your body or your reflex time.

By the end, a tree will have an answer too. It has no nerve cell — and still bends toward the light.