How does the reflex beneath the knee cap make your leg “swing” when you hit it?

Question

How does the reflex beneath the knee cap make your leg “swing” when you hit it?

In: 136

Answer 1

So, to stay standing up, we have sensory nerves called stretch receptors in the muscles and ligaments of the leg. They send signals to a nerve cluster that has motor nerves for the leg muscles. When you stand on your leg, the tensing and relaxing of your leg muscles keeps your balance. The stretch receptors activate the motor nerves for the muscle that got stretched. This is so that, if the pull on s muscle suddenly increases (maybe you stumble), the stretched muscle contracts automatically. The nerve signal does not have to travel all the way to the motor cortex in the brain, it can do it’s job using a shortcut.

When the doctor hammers the ligament below your kneecap, a big signal gets sent through this shortcut to make the muscles in your thigh contract.

Spastic cerebral palsy is s disruption of this loop.