The challenge
Sit on the edge of a chair so your lower leg hangs freely. Ask a partner to tap firmly just below your kneecap (patella) with the side of their hand. What happens?
Objective
Observe a spinal reflex arc directly and understand the difference between conscious and involuntary responses.
Materials
A partner and the edge of a chair.
Description
The patellar reflex is medically used to test the integrity of the L4 spinal nerve. Its speed (response time ~25 ms) is far faster than conscious reactions (>150 ms) because the signal never reaches the brain — it loops through the spinal cord only. This experiment is a vivid reminder that not all of your behavior is under your conscious control — and that the body has its own intelligence.
Source: https://en.wikipedia.org/wiki/Patellar_reflex
← All experiments