The nerves transfer signals between the central nervous system (brain, spinal cord) and other parts of the body. The motor fibers transfer information from the brain to muscles. Sensory fibers transfer information from our sensory organs in the skin to the brain, recognizing the senses of touch, pressure, temperature, and pain.The brachial plexus is a network of nerves in the neck that starts in the spine and controls muscle movement in the hands, arms and shoulders. The sensory nerves from the brachial plexus supply the entire upper extremity with the exception of the inner upper arm. The brachial plexus is formed by ventral rami of five spinal nerve roots – the lower four cervical (C5-8) and the first thoracic (Th1). In general, the C5 root is tasked with shoulder movement, C6 with elbow movement, and C7 facilitates the extension of the elbow and wrist. The C8 and Th1 control hand movements.An injury to the brachial plexus causes a partial or complete loss of movement and feeling in an upper extremity.
Anatomical illustration of the brachial plexus.

Anatomical illustration of the brachial plexus.