The bicep, like other muscles, is primarily controlled by the cerebrum, a section of the brain located just above the brain stem and the cerebellum. The peripheral nervous system relies on the cerebrum to send signals to the bicep's short and long heads so that they function as a single muscle as the bicep contracts during the curl.
Muscle movement depends on brain signals sent to each muscle. The signals provide information on what the brain wants the body to do. A bicep curl is a muscle contraction, which is controlled by the somatic region of the peripheral nervous system. Muscles use information sent by the somatic nervous system through neurons in the body. Neurons communicate with the central nervous system and, based on the signals they get, send directions about the action they want the affected muscle to do.
The bicep includes a long head and a short head that work together. The heads are attached to the proximal and distal bicep tendons. When tendons get a stimulus signal from the brain signaling a desire to move, a release of neurotransmitters stimulate the tendons. The stimulation of the tendons sends energy in the form of proteins and oxygen to that area, helping the bicep muscle to contract, or curl.