Home▸Neuroscience & Biophysics▸Muscle Spindles and the Stretch Reflex: How Muscles Sense Their Own Length

🦵 Muscle Spindles and the Stretch Reflex: How Muscles Sense Their Own Length

Explore how muscle spindles detect length and velocity of stretch, drive the monosynaptic knee-jerk reflex, and let gamma motor neurons keep the system sensitive during voluntary movement.

Neuroscience & Biophysics3DModerate60 FPS

This simulator visualizes how stretching a muscle lengthens its embedded spindle, driving Ia afferent firing that scales with both stretch magnitude and velocity, and how that signal travels a monosynaptic spinal arc to trigger a corrective muscle contraction.

🔬 What It Demonstrates

🎮 How to Use

Apply a stretch to the simulated muscle by adjusting length and speed, then watch the spindle's Ia afferent firing rate and the resulting reflex contraction, including the effect of toggling gamma motor neuron activity on spindle sensitivity.

💡 Did You Know?

The patellar reflex loop is so fast, completing in about 30 to 50 milliseconds, that it is often used clinically as a quick check of spinal cord integrity without needing any input from the brain at all.

⚙ Under the hood

Explore how muscle spindles detect length and velocity of stretch, drive the monosynaptic knee-jerk reflex, and let gamma motor neurons keep the system sensitive during voluntary movement.

proprioceptionmuscle-spindlestretch-reflexneurosciencephysiologymotor-controlpatellar-reflexbiomechanics

3D · Three.js / WebGL renderer · 60 FPS target · runs fully client-side, no install