A motor unit is made up of a motor neuron and the skeletal muscle fibers innervated by that motor neuron's axonal terminals.roups of motor units often work together to coordinate the contractions of a single muscle; all of the motor units within a muscle are considered a motor pool. All muscle fibers in a motor unit are of the same fiber type.
SURFACE STRUCTURE. Basaltic lava flows erupt primarily from shield volcanoes, fissure systems, scoria cones, and spatter cones. These fluid lava flows can be subdivided into two end-member structural types, based primarily on the nature of lava flow surfaces: 1  Pahoehoe Lava -- Surfaces are smooth, billowy, or ropy.
Basalt, cider, Obsidian, foamed obsidian & others are types of ingeous rock, Volcanic Rock. Liquid rock is not always called lava. When the liquid rock is still underground it is called magma. The differences between magma and lava is basically made to make geological occurrences easier to understand and explain. A volcano erupts when there is sufficient pressure underground from magma that contains gas bubbles.