LECTURE: Skeletal Muscle Biomechanics Introduction for A&P

Summary

This video explains key biomechanical principles for understanding muscle actions. It emphasizes the importance of knowing the origin and insertion of muscles, as well as how muscles only pull, never push. The video also outlines the movement of muscles, with the insertion moving towards the origin. It discusses the specific muscle actions for the humerus (flexion, extension, abduction, adduction) and the scapula (protraction, retraction, elevation, depression), helping viewers understand the biomechanical actions based on muscle location. The presenter encourages viewers to apply these principles while studying muscle actions for better retention and understanding.

Takeaways

• 😀 All muscles have two attachment points: the origin (stationary) and the insertion (mobile).
• 😀 The origin is the fixed attachment point, while the insertion is the part that moves during muscle action.
• 😀 Muscles only pull, never push. Any movement involves pulling the insertion toward the origin.
• 😀 The mobile attachment (insertion) always moves toward the stationary attachment (origin).
• 😀 The location of the muscle determines the bone that will move, as the muscle's insertion moves that bone.
• 😀 For the humerus, muscles can cause flexion, extension, abduction, or adduction, while the scapula moves via protraction, retraction, elevation, and depression.
• 😀 Understanding muscle actions requires knowing whether the muscle acts on the humerus or the scapula.
• 😀 For muscles acting on the humerus, those that are anterior to the glenohumeral joint (e.g., pectoralis major) will primarily flex the humerus.
• 😀 A muscle's insertion point dictates which direction the bone will move, following the general principle: insertion moves toward the origin.
• 😀 When studying muscle actions, use a biomechanic chart to identify and memorize specific actions of the humerus and scapula based on muscle locations.
• 😀 It's helpful to learn at least two actions for every muscle, although not all muscles will have two distinct actions.

Q & A

What are the two attachment points of a muscle?

The two attachment points of a muscle are the origin and the insertion. The origin is the stationary attachment that doesn't move, while the insertion is the mobile attachment that moves during muscle contraction.

What is the difference between the origin and the insertion of a muscle?

The origin is the stationary attachment point of the muscle, and it does not move during muscle contraction. The insertion is the mobile attachment point, which moves towards the origin during muscle action.

Why is it important to understand the biomechanical principles of muscle actions before memorizing them?

Understanding biomechanical principles helps to grasp the underlying 'why' behind muscle actions, which saves time and makes it easier to memorize the specific actions later.

Do muscles push or pull when creating movement?

Muscles only pull; they do not push. Any action performed by a muscle involves the mobile attachment (insertion) moving toward the stationary attachment (origin).

How do muscles create movement in bones?

Muscles create movement by inserting into bones. When a muscle contracts, the insertion (the mobile attachment) moves toward the origin (the stationary attachment), causing movement in the bone.

What is the key concept behind muscle insertion and origin in relation to body movement?

The key concept is that the insertion (mobile attachment) always moves towards the origin (stationary attachment), leading to movement in the bone that the muscle is attached to.

What is the difference between humerus muscle actions and scapula muscle actions?

Humerus muscle actions include flexion, extension, abduction, and adduction, while scapula muscle actions include protraction, retraction, elevation, and depression. Each group corresponds to specific movements of either the humerus or the scapula.

Can muscles that insert into the humerus perform both flexion and extension?

Yes, muscles that insert into the humerus can perform different actions such as flexion (moving the arm forward) or extension (moving the arm backward), depending on their location relative to the joint.

Why is it important to understand the location of a muscle in relation to the joint it crosses?

The location of a muscle relative to a joint helps determine the muscle's action. For example, muscles that cross a joint anteriorly typically perform flexion, while those that cross it posteriorly often perform extension.

How can you use the biomechanical chart to learn muscle actions?

By referencing the biomechanical chart, you can determine the action of a muscle by examining its location and its insertion point. This chart helps identify whether a muscle will perform flexion, extension, or other specific actions based on its attachment points.