Lab 7 The Muscular System BIO201L Straighterline Anatomy and Physiology 1 Lab BIO201L Lab 7 The Muscular System Worksheet 2023

Pre-Lab Questions 1. How do banding patterns change when a muscle contracts? When a muscle contracts, the banding patterns within the muscle change due to the sliding filament theory of muscle contraction. This theory suggests that muscle contraction occurs when thin filaments (actin) slide over thick filaments (myosin), resulting in the overlapping of these filaments and shortening of the sarcomeres, which are the basic contractile units of the muscle. As a result, the dark A bands, which consist of overlapping myosin filaments, stay relatively constant in length, while the light I bands, which contain only actin filaments, shorten. The H zone, located in the middle of the A band, also narrows or disappears altogether. These changes in the banding patterns reflect the molecular events that occur during muscle contraction. 2. What is the difference between a muscle organ, a muscle fiber, myofibril and a myofilament? a muscle organ refers to the entire structure composed of muscle tissue, connective tissue, blood vessels, and nerves, which work together to produce movement. A muscle fiber, also known as a muscle cell, is a single elongated cell within the muscle organ that contains myofibrils. Myofibrils are cylindrical structures within muscle fibers composed of repeating units called sarcomeres, which are responsible for muscle contraction. Finally, myofilaments are the protein filaments found within the sarcomeres, with two main types: thick filaments (myosin) and thin filaments (actin). Myofilaments interact with each other to generate muscle contraction by the sliding filament theory. In summary, a muscle organ contains muscle fibers, which house myofibrils that are made up of myofilaments responsible for muscle contraction.