What reflex causes reciprocal activation of the antagonist muscle, especially to maintain balance?
Tendon
Crossed-extensor
Flexor
Muscle stretch
The correct answer and explanation is:
The correct answer is reciprocal inhibition.
Reciprocal inhibition is a reflex that causes the antagonist muscle to relax while the agonist muscle contracts. This reflex is crucial in maintaining coordinated movement and balance. It ensures that when one muscle contracts to produce movement, its opposing muscle (the antagonist) is simultaneously inhibited to allow the desired motion to occur without resistance.
For example, when you flex your bicep muscle (agonist), the triceps muscle (antagonist) is inhibited, making it easier for the bicep to contract and perform the movement. This is particularly important in activities such as walking, where maintaining balance and fluid movement requires constant adjustments between opposing muscle groups.
The process works through neural circuits in the spinal cord, where sensory neurons detect muscle stretch and send signals to the spinal cord. These signals then activate motor neurons to stimulate the contraction of the agonist muscle. Simultaneously, interneurons inhibit the motor neurons controlling the antagonist muscle, preventing it from contracting and opposing the motion.
Reciprocal inhibition is essential for balance because it prevents muscle stiffness and allows for smooth, controlled movement. For instance, during a reflexive response to a sudden loss of balance, the body automatically adjusts by contracting certain muscles and relaxing others, allowing for quick and effective stabilization.
This mechanism is not only critical for voluntary movements like walking or running but also for reflex actions such as the withdrawal reflex, where the body pulls away from a painful stimulus. By ensuring that antagonist muscles relax when necessary, reciprocal inhibition helps maintain posture, balance, and coordinated movement in everyday activities.