brachial plexus, plexus brachialis(noun)

a network of nerves formed by cervical and thoracic spinal nerves and supplying the arm and parts of the shoulder

Brachial Plexus

The large network of nerve fibers which distributes the innervation of the upper extremity. The brachial plexus extends from the neck into the axilla. In humans, the nerves of the plexus usually originate from the lower cervical and the first thoracic spinal cord segments (C5-C8 and T1), but variations are not uncommon.