## Step3

The patellar reflex

When somebody hits your petallar tendon (just underneath your patella), your lower leg will kick up by itself! This is known as the patellar reflex (also called the knee-jerk reflex). In normal situations, the patellar reflex helps to stand up straight and balance without having to think about it.

For more information watch this video.

When somebody hits your patellar tendon, sensory neurons in your thigh pick up the stretch and send an impulse to your spinal cord (to the right you see a cross-section of the spinal cord). In the spinal cord the impulse is sent directly to the motor neurons which activate the muscle.

Below you will see a couple of parts of the human body.

A. leg muscle (quadriceps)

B. cerebrum

C. cerebellum

D. sensory neuron

E. motor neuron

F. clavicle

G. interneuron

Of these words, only four are involved with the patellar reflex.

Which of the parts are involved?

Put those parts in the right order.

Answer: ... - ... - ... - ...

Extra assignment:

If you focus, you can stop the patellar reflex from taking place. A man named Ernő Jendrassik observed something strange. When a patient would hold their hands like in the picture below, they were not able to stop the leg from kicking up.

When a patient is holding their hands like in the picture and focus on pulling outwards, this inhibits the knee-jerk reflex. This is called 'the Jendrassik maneuver' after its inventor.

Try the following things yourself:

- Have your partner hit your patellar tendon with a small object.
- Try not to move your leg while somebody hits the patellar tendon.
- Do the Jendrassik maneuver and try not to move your leg while somebody hits the patellar tendon.