In some people, this muscle contracts under dim light conditions.

Large amounts of these are found in muscle cells, and help muscles contract.

"That all takes energy to make those muscles contract."

The nerves control various sensations and the ability to make muscles contract.

When you have asthma, these muscles contract, making the airways narrow and small.

When this muscle contracts, it reduces the size of the pupil.

The current made the muscles contract and flex his foot.

You may receive medicines to make the uterine muscles contract.

It took energy to make their muscles contract, and starving members had no energy to work with.

When a muscle contracts, or shortens, its job is to bring the bones closer together for movement.