What is a muscle?

What is a muscle?

• A. cells that conduct electrical impulses
• B. cells that contract to cause movement
• C. protective covering of the eye
• D. a fluid in the eye

Answer: (B)

Muscles are tissues made of muscle fibers that contract to produce movement. When these fibers shorten, they pull on tendons attached to bones or other structures, enabling actions like bending a arm or lifting a leg. The essential trait of muscle tissue is its ability to contract, which is triggered by nerve signals and uses energy from ATP. That makes the description “cells that contract to cause movement” the best match. The other options describe nerve cells that carry impulses, the protective covering of the eye, and a fluid in the eye, none of which are what a muscle is.

Muscles are tissues made of muscle fibers that contract to produce movement. When these fibers shorten, they pull on tendons attached to bones or other structures, enabling actions like bending a arm or lifting a leg. The essential trait of muscle tissue is its ability to contract, which is triggered by nerve signals and uses energy from ATP. That makes the description “cells that contract to cause movement” the best match. The other options describe nerve cells that carry impulses, the protective covering of the eye, and a fluid in the eye, none of which are what a muscle is.