Physical Therapy Assistant Practice Exam 2026 – Complete Prep Guide

The middle trapezius muscle is primarily innervated by the accessory nerve, which is cranial nerve XI. This nerve is responsible for motor function of certain neck and shoulder muscles, including the trapezius. The trapezius is a large muscle that plays an essential role in stabilizing and moving the shoulder as well as supporting the head.

The accessory nerve provides innervation for the upper and middle sections of the trapezius, which are crucial for actions like shoulder elevation and scapular retraction. Understanding the role of the accessory nerve is vital for recognizing how to assess and treat conditions affecting the trapezius, as well as for developing physical therapy treatment plans.

Other nerves mentioned have different functions: the dorsal scapular nerve innervates the rhomboid muscles and the levator scapulae, the long thoracic nerve innervates the serratus anterior muscle, and the thoracodorsal nerve supplies the latissimus dorsi muscle. Each of these nerves serves specific muscles in the shoulder and back region but does not provide innervation to the middle trapezius. This understanding clarifies how to properly address muscle functions and potential issues in physical therapy practice.