Tissue that shortens

Clench your fist, closing your hand tight. The muscle cells in your forearm, between wrist and elbow, shorten.

Rule

Muscle tissue moves the body by shortening. Skeletal muscle is voluntary. Smooth and cardiac muscle are involuntary.

• Voluntary — you choose the movement, like writing.
• Involuntary — it happens on its own, like the heartbeat.

Skeletal muscle is attached to bones. When it shortens, it pulls on a bone. So the body moves. A joint is where bones meet.

Smooth muscle is in the stomach and intestine. This muscle moves food slowly along. Cardiac means of the heart. Cardiac muscle is only in the heart. This muscle beats all through life and resists tiring.

Nervous tissue tells muscles when to work.