<p> Essays for chapters 48-49</p><p>1. Discuss how cellular structures, including the plasma membrane, specialized endoplasmic reticulum, cytoskeletal elements, and mitochondria, function together in the contraction of skeletal muscle cells.</p><p>2. Beginning at the presynaptic membrane of the neuromuscular junction, describe the physical and biochemical events involved in the contraction of a skeletal muscle fiber. Include the structure of the fiber in your discussion</p><p>3. Describe the structure and function of the reflex arc in higher vertebrates. Include a description of the cell types and a discussion of the mechanism of transmission of the impulse.</p><p>4. Describe in detail, how the structure of the eye and ear contribute to the process of seeing and hearing.</p>