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If The Brain Controls The Body Why Does Your Knee Jerk When The Doctor Hits IT?

Why does your knee jerk? Have you ever thought about the reasoning behind why humans have this reflex?

These reflexes happen involuntarily when certain #nerves 'fire’ and sidestep the conscious parts of your brain!

Your #StretchReflexes also help keep you standing upright, which you’ll quickly notice if you start tipping to one side as these reflexes automatically through human evolution correct your upright balanced position to prevent falling and potential injury.

“Basically when the muscle spindle perceives the muscle is being stretched, it initiates a signal, causing the stretched muscle to contract (shorten) forcefully. It does this in order to oppose the stretching from whatever external force is involved,” - Dr. Van Vuuren.

The muscle spindle and fibers in the frontal upper leg muscles (the quadriceps) cause the #KneeJerkReflex also called #PatellarJerk, although the actual reflex starts when your doctor taps your knee.

This reaction is one of the few that humans conduct without sending ANY signals to the brain!

In simple terms, your doctor is tapping the kneecap (patella) tendon that spans across the front of the knee and keeps the kneecap in position.

The #PatellarTendon connects to the quadriceps muscle via the kneecap (the patella) and the quadriceps tendon.

When this tendon is tapped by the doctor, it causes a minimal stretching of the muscle fibers in the quadriceps. This sends a signal to the #SpinalCord which then relays two different signals back.

One of these signals stimulates the contraction of the quadriceps muscle also called the stretch reflex. At the same time, the second signal encourages the muscle at the back upper leg (the hamstrings) to relax, resulting in that knee kick then release!

Now you know why your knee jerks when you hit the bottom of your knee cap sitting down! Did you find this article interesting? If so please like and comment on what kind of other interesting neuroscience or marketing-related topics to cover. Thank you!

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