Question

We can contract different divisions of the trapezius muscle at different times. This allows it to be its own antagonist as it can both ____ and _____ the ____.

Answer 1

The trapezius muscle functions as its own antagonist by contracting different fibers to elevate and depress the scapula. It's capable of different actions by selective activation of its fibers, with its upper and lower parts opposing each other's actions.

Step-by-step explanation:

We can contract different divisions of the trapezius muscle at different times. This allows it to be its own antagonist as it can both elevate and depress the scapula.

The trapezius muscle, innervated by the accessory nerve, attaches to the head, trunk, and shoulders and is capable of performing various movements of the scapula including elevation, depression, retraction, and rotation. Depending on which fibers are activated, it can serve multiple roles. For instance, the upper fibers elevate the scapula, while the lower fibers can act as an antagonist to the upper fibers by depressing the scapula.

Muscles often work in pairs where one muscle, the agonist, causes a movement and the antagonist muscle acts in opposition to it. However, the trapezius muscle is unique in that it can act as its own antagonist due to its ability to contract in localized areas. This flexibility in movement underscores the intricate design of muscle and skeletal interactions, where muscles like the trapezius can perform multiple actions to facilitate complex bodily movements.