Disorders of Muscular and Skeletal System
தசை மற்றும் எலும்புக்கூட்டு மண்டலக் கோளாறுகள்
Myasthenia gravis is autoimmune; muscular dystrophy is genetic. Tetany comes from LOW calcium, not high. These three swaps cost students marks every single year.
The idea
Myasthenia gravis is an autoimmune disorder affecting the neuromuscular junction, leading to fatigue, weakening and paralysis of skeletal muscle. Muscular dystrophy is the progressive degeneration of skeletal muscle, mostly due to a genetic disorder. Tetany is rapid spasms (wild contractions) in muscle due to low Ca2+ in body fluid. Arthritis is inflammation of joints. Osteoporosis is an age-related disorder characterised by decreased bone mass and increased chances of fractures; decreased levels of estrogen are a common cause. Gout is inflammation of joints due to accumulation of uric acid crystals.
Why it matters
Muscles and bones depend on nerves, immunity, minerals and hormones; a fault in any one of these shows up as a specific disorder.
NEET lens
Six NCERT disorders: myasthenia gravis — autoimmune, neuromuscular junction; muscular dystrophy — genetic, progressive degeneration (the inherited one); tetany — low Ca2+, rapid spasms; arthritis — inflamed joints; osteoporosis — decreased bone mass, decreased estrogen (estrogen and parathyroid hormone are the hormones linked to it); gout — uric acid crystals in joints. Assertion-reason: 'increased estrogen causes osteoporosis' is false.
Clinical significance
Women after menopause lose estrogen and are at high risk of osteoporosis; calcium, vitamin D and weight-bearing exercise help prevent fractures. Gout is managed by lowering blood uric acid through diet and medicines.
Introduction
NCERT lists six disorders of the muscular and skeletal system — each with one defining cause or feature that NEET tests.
Core concept
Myasthenia gravis: autoimmune disorder of the neuromuscular junction → fatigue, weakening, paralysis of skeletal muscle. Muscular dystrophy: progressive degeneration of skeletal muscle, mostly genetic. Tetany: rapid spasms (wild contractions) due to low Ca2+ in body fluid. Arthritis: inflammation of joints. Osteoporosis: age-related; decreased bone mass, more fractures; common cause = decreased estrogen. Gout: inflammation of joints due to accumulation of uric acid crystals.
Go deeper
Parathyroid hormone raises blood Ca2+ partly by stimulating bone resorption, so excess PTH also weakens bones — this is why 'estrogen and parathyroid hormone' is the answer for hormones that play a role in osteoporosis.
From Class 10
These are diseases of muscles, bones and joints you may have heard of in elderly relatives — arthritis, gout, osteoporosis. NEET asks the exact cause of each.