Question 1: Explain how muscles work in pairs during movement, using the example of arm flexion and extension.

Answer: Muscles work in pairs called antagonistic pairs. During arm flexion, the biceps contract while the triceps relax; during extension, the triceps contract while the biceps relax, allowing smooth movement.

Question 2: Describe the structure of a skeletal muscle, including the role of muscle fibers.

Answer: A skeletal muscle is made up of many muscle fibers bundled together. Each fiber is a long, cylindrical cell that contracts in response to nerve signals, enabling muscle movement.

Question 3: Sketch a simple diagram of a muscle cell and label its key parts, such as the nucleus, myofibrils, and sarcomere.

Answer: A correct sketch would show a long, cylindrical muscle cell (fiber) with multiple nuclei along its sides, with internal myofibrils running parallel, and segments labeled as sarcomeres (the contractile units).

Question 4: Identify two common injuries to muscles and briefly explain how they occur.

Answer: Strains occur when muscles are overstretched or torn, often from sudden movements or overload. Muscle cramps are involuntary contractions caused by dehydration, electrolyte imbalances, or fatigue.

Question 5: Draw a diagram illustrating the process of muscle contraction, including the roles of actin, myosin, and energy (ATP).

Answer: The diagram should depict actin and myosin filaments sliding past each other within the sarcomere, powered by ATP, leading to muscle shortening.