[HAP-10] Musculoskeletal System, Neuromuscular Junction, Bone Remodelling & Joint Pathophysiology
HAP-10 • 9. PathophysiologyLearning Objectives
Trace neuromuscular junction (NMJ) transmission (ACh release → nicotinic NM receptor → T-tubule DHPR → SR Ryanodine receptor RyR1 Ca2+ release → Troponin C/Actin–Myosin cross-bridge cycling).; Contrast depolarizing ([12.32] Succinylcholine/Suxamethonium) vs competitive non-depolarizing neuromuscular blockers (Vecuronium, Rocuronium, Atracurium) and reversal with [11.39] Neostigmine + [12.33] Atropine / [12.38] Glycopyrrolate.; Compare Osteoporosis (RANKL/Osteoprotegerin balance, Bisphosphonates, [10.9] Calcium + [10.12] Vitamin D3), Osteoarthritis, Rheumatoid Arthritis, and Myasthenia Gravis.
Chapter Overview & Core Explanation
Skeletal movement depends on motor nerves releasing acetylcholine onto muscle fibres, triggering an internal wave of calcium that makes actin and myosin filaments slide past each other, anchored to a living skeleton that constantly rebuilds itself through osteoblasts and osteoclasts.
Key Exam & Clinical Takeaways
- [11.39] Neostigmine reverses non-depolarizing neuromuscular blockers (Vecuronium, Rocuronium, Atracurium) but must always be paired with [12.38] Glycopyrrolate or [12.33] Atropine to block muscarinic bradycardia.
- Oral Bisphosphonates (Alendronate) must be taken first thing in the morning with a full glass of plain water while remaining upright for ≥30 minutes to prevent erosive oesophagitis.