Inhibition of the Ia afferent synapse onto antagonist motor neurons during a muscle stretch reflex is termed:

• A Reciprocal inhibition via Ia inhibitory interneurons ✓
• B Presynaptic inhibition via Renshaw cell activation
• C Postsynaptic inhibition via Golgi tendon organ Type Ib afferents
• D Surround inhibition via lateral inhibition in the posterior horn

Explanation

When muscle spindle Ia afferents fire during stretch, they directly excite the homonymous alpha motor neurons (monosynaptic stretch reflex). Simultaneously, Ia afferents send collaterals to Ia inhibitory interneurons in the spinal cord that inhibit the alpha motor neurons of the antagonist muscle (reciprocal innervation). This ensures coordinated movement where agonist contraction is accompanied by antagonist relaxation. Renshaw cells provide recurrent collateral inhibition of the same motor neuron that activated them.

Reference: Guyton & Hall, Textbook of Medical Physiology, 14th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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