So once again the single unit smooth muscle is the most common type of arrangement of smooth muscles in the human body. Single unit smooth muscles consist of an innervating neuron that causes one or several of the smooth muscles to contract. The action potential then travels through the other smooth muscles via gap junctions between adjacent cells. So basically, as soon as the action potential is received by this cell, shown in red, is then split to the other cells and the same thing happens in this particular case. So this red arrow basically describes the movement of our action potential. So this sort of arrangement allows the group of smooth muscles to contract as a single unit as a whole.