Which of the following structures contains multi-unit smooth muscle rather than single-unit (visceral) smooth muscle?
- A Wall of the ureter
- B Ciliary muscle of the eye ✓
- C Body of the urinary bladder
- D Muscularis propria of the stomach
Correct answer: B. Ciliary muscle of the eye
Explanation
Multi-unit smooth muscle consists of discrete fibres each receiving its own autonomic innervation with little electrical coupling, allowing fine graded control. Classic examples are the iris, ciliary muscle, piloerector muscles and vas deferens. Bladder detrusor, ureter and gastrointestinal muscle are single-unit syncytia joined by gap junctions and driven largely by myogenic slow waves, so they behave as one functional unit instead of independently controlled fibres.
Reference: Ganong's Review of Medical Physiology, 26th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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