A reflex that causes reciprocal activation of the antagonist muscle is the
a. Crossed-extensor
b. Flexor
c. Tendon
d. Muscle stretch

Reciprocal inhibition is a physiological process where the activation of one muscle (the agonist) leads to the simultaneous relaxation of its antagonist muscle. This mechanism is crucial for coordinated movement, allowing for smooth transitions between muscle contractions and relaxations. For example, when you flex your arm, the biceps contract while the triceps relax.

Reflex arcs are neural pathways that mediate reflex actions. They typically involve sensory neurons, interneurons, and motor neurons, allowing for rapid responses to stimuli without direct involvement of the brain. In the context of muscle activation, reflex arcs can facilitate reciprocal inhibition, ensuring that when one muscle contracts, its antagonist relaxes to prevent injury and maintain balance.

There are several types of reflexes, including flexor, crossed-extensor, and tendon reflexes. The flexor reflex involves the withdrawal of a limb from a painful stimulus, while the crossed-extensor reflex helps maintain balance by activating the opposite limb. Understanding these reflex types is essential for identifying how muscles interact during various movements and responses.