Normally, the coordinated action of the muscles of the stomach and small intestine propels the food from the stomach, through the small intestine and into the colon. This muscular action also sweeps bacteria out of the small intestine and limits the numbers of bacteria in the small intestine.
The term 'motor neuron' is usually restricted to the efferent neurons that actually innervate muscles (the lower motor neurons). A single motor neuron may innervate many muscle fibres and a muscle fibre can undergo many action potentials in the time taken for a single muscle twitch.
Definition of Motor Unit. A motor unit consists of one somatic efferent (motor) neuron and all of the muscle fibers (cells) that it innervates. In the figure to the right, two motor units are illustrated diagrammatically.Notice that after an efferent axon enters the muscle, it branches and forms synapses with a number of muscle fibers. motor unit consists of one somatic efferent (motor) neuron and all of the muscle fibers (cells) that it innervates.