Flex - when muscles contract to bend joints
Extend - when muscles relax to straighten joints
Joint - a place in the body where muscles bring about movement
Antagonistic - muscles only pull they don't push. A pair of muscles that work together that pull to extend or flex a joint are called an antagonistic pair of muscles.
Flexor - a muscle that contracts to flex a muscle. E.g. the hamstring muscles contract to bend the knee.
Extensor - a muscle that contracts to cause an extension of a joint. E.g. the quadriceps contract to straighten out the knee.
Synovial joints - the bones that move in the joint are separated by a cavity filled with synovial fluid.
Synovial fluid - a fluid that enables joints to move freely. It acts like a lubricant.
Ligaments - joins bones to bones. Must be strong and flexible.
Tendons - joints muscle…