An extensor muscle is any skeletal muscle that opens a joint increasing the angle between components of a limb, such as straightening the knee or elbow and bending the wrist or spine. With the exception of the knee joint the movement is directed backward. Structure of a skeletal muscle Skeletal muscle is a type of striated muscle, attached to the skeleton. ... An x-ray of a human knee In human anatomy, the knee is the leg joint connecting the femur and the tibia. ... Elbow redirects here. ... In human anatomy, the wrist is the flexible and narrower connection between the forearm and the hand. ... The vertebral column seen from the side The vertebral column (backbone or spine) is a column of vertebrae situated in the dorsal aspect of the abdomen. ...
The type of muscle that has the opposite effect is the flexor muscle, which closes a joint, decreasing the angle between limb components. A flexor muscle is a skeletal muscle whose contraction bends a joint, decreasing the angle between components of a limb, such as bending the knee or elbow. ...
In humans, some muscles include 'extensor' in their name, some include;
These include the skeletal muscles which are under voluntary control and are made of striated muscle tissue, the visceral muscles which are under involuntary control and are made of smooth muscle tissue, and cardiac muscle tissue which is found only in the heart.
After a muscle contracts, ATP (produced in the muscle cellsÂ’ mitochondria) is needed to relax the muscle and return the actin and myosin filaments to their normal positions.
Muscle contraction is initiated when an electrical impulse from a nerve cell reaches its associated muscle cell(s), causing positively- and negatively-charged ions to switch places all along the muscle cell (fiber).
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