David’s case of muscle weakness

1.David, a 6-year-old boy, has recently had trouble walking; he has difficulty maintaining his balance and often falls. His parents took him to see their family physician. Dr. Gazo performed a physical examination and blood tests on David and collected a family history from his parents. Based on the results, the doctor diagnosed David with Duchenne muscular dystrophy (DMD). This disease is caused by a mutation in a single gene which leads to progressive muscle deterioration.

2.The gene that is mutated in DMD gives rise to a protein which is important to the function of all striated muscle. Which type(s) of muscle would be affected in a patient with DMD?(1 pt)

3,All three types of muscle contain myofilaments which slide against each other to contract the muscle. What protein composes the thick filaments? What protein composes the thin filaments? With which myofilament is troponin associated? (3 pts)

4. What is the role of calcium in the muscle contraction? (What does calcium do and why is it necessary in muscle contraction?) (2 pts)

5. The nerves that control muscles are usually not affected in DMD. What neurotransmitter is released by motor neurons? (1pt)

6. What is a motor unit? Which would contain larger motor units: David’s semimembranosus or his buccinator? (3 pts)

7. As the disease progresses, David may require a ventilator to assist in breathing. Identify the muscle which contributes most to ventilation (moving air in and out of the lungs). What type of muscle is it? (3 pt)

8. David’s test revealed an elevated level of creatine kinase in his blood. Why would the presence of creatine kinase in the blood indicate the breakdown of muscles? (2 pts)

9. What is the function of creatine kinase? (3 pts)

10. As his muscles weaken, a wheelchair will allow David to maintain his mobility. His bones may also weaken although they are not directly affected by the DMD mutation. Explain why decreased movement leads to bone weakness and identify the law that relates muscle use to bone strength. (2 pt)

11. List and describe the function of the three main types of cells found in bone. (3 pts)

12. Which of the three bone cell types is stimulated by parathyroid hormone? (1 pt)

13. What effect does parathyroid hormone have on calcium levels in the blood? (1 pts)

14. Describe the composition of osteoid and hydroxyapatite of bone matrix. (1 pt)

15. Describe the functions of osteoid and hydroxyapatite of bone matrix. (1 pt)

16. Current treatments for DMD are mainly supportive, that is, they help support the healthy muscle tissue and maintain mobility. There are many avenues of research on ways to reverse or even cure DMD. One of these avenues involves drugs that help the body to better repair muscle tissue as it is damaged. Based on your knowledge of wound healing processes, what type of tissue is formed to replace normal muscle tissue that is broken down in DMD patients? (3 pts)