Jason Boyle, Ph.DOur muscles are controlled by “motor units”, which each consist of a neuron, and the muscle fiber(s) it activates or “innervates”. The muscle that responds is termed an “effector”. Brain mapping studies have shown that a disproportionate area of the motor cortex governs certain effectors of the body. For example, your fingers, lips, and tongue are highly innervated organs that can execute complex movement patterns, but your toes are not ...