Sustained tension in a muscle activates receptors that discharge via Ib afferents, producing disynaptic inhibition of the homonymous alpha motor neurons. Which structure mediates this response?
- A Muscle spindle nuclear bag fiber
- B Pacinian corpuscle in the joint capsule
- C Golgi tendon organ ✓
- D Free nerve ending in the muscle fascia
Correct answer: C. Golgi tendon organ
Explanation
The Golgi tendon organ lies in series with muscle fibers at the musculotendinous junction, senses tension rather than length, and signals via Ib afferents. Ib afferents excite an inhibitory interneuron that suppresses homonymous alpha motor neurons, producing autogenic (inverse stretch) relaxation. The muscle spindle lies in parallel and signals length via Ia and II afferents, which is what distinguishes it from this tension-sensitive circuit.
Reference: Ganong's Review of Medical Physiology, 27th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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