Innervation of the Pectoralis Minor. In order for a muscle to contract and function, it must receive electrical impulses from the brain through a nerve or group of nerves, a process that is called innervation. The pectoralis minor muscle is innervated by the medial pectoral nerve. The medial pectoral nerve contains nerve fibers from the eighth cervical nerve (C8), which comes from the spine in the lower part of the neck, and the first thoracic nerve (T1), which comes from the spine in the upper part of the back. Lesson Summary. The pectoralis minor muscle is a