And in this particular case, the motor unit only consists of a single muscle cell and a single motor neuron. Now a single motor neuron always consists of a single neuron but it can have thousands of muscle cells. So we have thousands of these different types of muscle cells in a bundle and that is our motor neuron. Now, within the muscle cell we have many of these fibers known as myofibrils. And these myofibrils themselves consist of the Sarcomir units. So Sarcomir units consist of the myosin and the actin protein.