What is reciprocal inhibition?

• A. Decreases Antagonist Opposition to the Action of Agonist Muscle
• B. Increases Antagonist Opposition to the Action of Agonist
• C. Co-activates Agonist and Antagonist
• D. Blocks Sensory Feedback

Answer: (A)

Reciprocal inhibition is the nervous system’s way of coordinating movement by dampening the opposing muscle when a muscle is activated to move. When the agonist contracts, sensory input from that contracting muscle (Ia afferents) activates inhibitory interneurons in the spinal cord, which suppress the motor neurons to the antagonist. This reduces the antagonist’s activity, so there’s less opposing force and the movement can occur smoothly and efficiently. It’s different from co-activation, where both muscles would fire together and resist movement. It also doesn’t involve blocking sensory feedback; sensory information remains, but the motor output to the antagonist is inhibited to facilitate the action.