Which sensory nerve is involved in muscle contraction and lengthening?

The Golgi tendon organ is the correct answer because it plays a crucial role in sensing changes in muscle tension and helps regulate muscle contraction and relaxation. Specifically, these sensory receptors are located at the junction between muscles and tendons and provide feedback to the central nervous system regarding the amount of force being exerted by the muscle. When muscle tension becomes too high, the Golgi tendon organs activate a reflex that inhibits further contraction and promotes relaxation, thereby preventing injury.

This feedback mechanism is essential for maintaining appropriate muscle length during activities such as weightlifting or any dynamic movements, as it helps ensure that muscles do not contract excessively and risk strain or damage. In contrast, other options such as the sarcomere, neuromuscular junction, and myofibril refer to structural components or sites of action within muscle fibers, but they do not specifically relate to the sensory feedback system involved in muscle contraction and lengthening.