Nerve and Muscle Physiology — MCQs

Question 471: What do muscle spindles primarily detect?

• A. Joint position changes
• B. Muscle tension changes
• C. Muscle length changes (Correct Answer)
• D. Muscle velocity changes

Explanation: ***Muscle length changes*** - **Muscle spindles** are specialized **stretch receptors** located within the muscle belly. - Their primary function is to detect the **rate of change in muscle length** and the absolute muscle length. *Muscle tension changes* - **Golgi tendon organs (GTOs)**, not muscle spindles, are responsible for detecting changes in **muscle tension**. - GTOs are located in the **tendons** and provide information about the force generated by muscle contraction. *Joint position changes* - While muscle spindles indirectly contribute to **proprioception** (sense of joint position), other **mechanoreceptors** like **Ruffini endings** and **Pacinian corpuscles** in joint capsules and ligaments are more directly involved in sensing joint position. - Muscle length changes are distinct from overall joint position, though related. *Muscle velocity changes* - While muscle spindles do detect the **rate of change** of muscle length, which relates to velocity, their primary role encompasses both static length and dynamic changes. - The most direct and comprehensive descriptor of their main function is detecting "muscle length changes."