Muscles Practice Test. Instructions: Scroll through each of the images and name the muscle identified. Check your answers with the key when you are finished. This is intended to be a study aid before you take the real test. You may want to reference the lab guide as you do the test and then later try to do the test without the guide. Skeletal muscle is innervated by somatic (as opposed to autonomic) motor axons at a synaptic structure called a motor endplate, where acetylcholine is the neurotransmitter. Most skeletal muscles can be controlled consciously, and skeletal muscle is sometimes referred to as voluntary muscle. Outgrowth of cells from skeletal muscle tissue explants. (A) Schematic representation of the protocol for myoblast isolation. (B) Outgrowth of cells from the skeletal muscle tissue of a 4-month old mouse on matrigel-coated vs. collagen-coated dishes at 1, 3, and 5 days after seeding. Immediately following the arrival of the stimulus at a skeletal muscle cell there is a short period called the _____ period during which the neurotransmitter is released by exocytosis, diffuses across the synaptic cleft, and binds to its receptors.