Understanding the human muscular system requires more than just memorizing the names of muscles; it requires a deep understanding of how those muscles move the body. In anatomy, we describe these movements through specific "actions." By mastering the vocabulary of muscle actions—such as flexion, extension, and abduction—you can predict how a specific muscle will move a joint or a limb based on its location and function.
The Fundamentals of Muscle Action
Muscle action refers to the specific movement produced by the contraction of a muscle. Muscles typically work in groups to move bones at joints. While some muscles are responsible for large, sweeping movements like walking, others are responsible for minute adjustments, such as the movement of the eyes.
To understand these actions, it is helpful to categorize them by the type of movement they produce. Whether you are looking at a model of the arm or a diagram of the face, the terminology remains consistent.
Primary Joint Movements
Most muscle actions are described in relation to the anatomical position of a limb or body part.
Flexion and Extension
Flexion is a movement that decreases the angle between two body parts, such as bending the elbow. For example, the biceps brachii is a primary muscle responsible for the flexion of the forearm.
Extension is the opposite of flexion; it is a movement that increases the angle between two body parts. The triceps brachii is the classic example of an extensor, as it is responsible for the extension of the forearm. In the lower body, the gluteus maximus performs extension of the thigh.
Keep reading for free.
Create an account to finish this reading and make it part of your study routine.
Continue reading freeAlready have an account? Log in
Updated