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.
A shield volcano is a type of volcano usually built almost entirely of fluid magma flows. They are named for their large size and low profile, resembling a warrior's shield lying on the ground. This is caused by the highly fluid lava they erupt, which travels farther than lava erupted from stratovolcanoes.This results in the steady accumulation of broad sheets of lava, building up the shield volcano's distinctive form. Shield volcanoes contain low-viscosity magma, which gives them flowing mafic lava.his is caused by the highly fluid lava they erupt, which travels farther than lava erupted from stratovolcanoes. This results in the steady accumulation of broad sheets of lava, building up the shield volcano's distinctive form. Shield volcanoes contain low-viscosity magma, which gives them flowing mafic lava.