What happens to the antagonist during reciprocal inhibition?

• A. It Is Inhibited by the Inhibitory Interneuron
• B. It Is Activated
• C. It Remains Uninvolved
• D. It Contracts After the Agonist

Answer: (A)

During reciprocal inhibition, activating the agonist muscle at a joint triggers an inhibitory interneuron in the spinal cord that suppresses the antagonist motor neurons. This inhibition reduces the antagonist’s activity, so it doesn’t oppose the movement and the limb can move smoothly. For example, when the elbow flexes by contracting the biceps, the triceps is inhibited so it doesn’t contract. This setup prevents opposing forces and favors coordinated action. The other options don’t fit because activating the antagonist would oppose the movement, remaining uninvolved wouldn’t allow coordinated control, and contracting after the agonist would not reflect the immediate inhibitory coordination that allows the movement to occur.