Sort the six disorders into those that affect the muscles and those that affect the joints and the…
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Sort the six disorders into those that affect the muscles and those that affect the joints and the bones. Give the cause of each, as NCERT gives it.
Myasthenia gravis, muscular dystrophy, tetany, arthritis, osteoporosis, gout.
Need a reminder? The key ideaShow
Joints are fibrous (no movement), cartilaginous (limited) or synovial (much movement: ball and socket, hinge, pivot, gliding, saddle). Myasthenia gravis, muscular dystrophy and tetany affect muscle. Arthritis, osteoporosis and gout affect joints and bones. For a lever at rest, effort times its distance from the fulcrum equals load times its distance from the fulcrum.
The worked solution
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Work it out on paper first. It is fine to get stuck or make a mistake: that is how we learn. When you are ready, go through the solution one step at a time, and check each step against your own.
Step 1. The muscles.
- Myasthenia gravis: an autoimmune disorder at the neuromuscular junction. It causes fatigue, weakening and paralysis of skeletal muscle.
- Muscular dystrophy: progressive degeneration of skeletal muscle, mostly genetic.
- Tetany: rapid spasms of muscle, because of a low level of Ca in the body fluid.
Step 2. The joints and the bones.
- Arthritis: inflammation of the joints.
- Osteoporosis: age related loss of bone mass, with more fractures. A decrease in oestrogen is a common cause.
- Gout: inflammation of the joints, because uric acid crystals collect in them.
Answer: Muscles: myasthenia gravis, muscular dystrophy, tetany. Joints and bones: arthritis, osteoporosis, gout.
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