Teach them a lesson they'll never forget! The Myotatic Reflex...

Teach your students a lesson they'll never forget with the myotatic reflex! Use this free protocol to have your students compare the joint angle and latency of the myotatic reflex under normal conditions and while performing the Jendrassik maneuver.


What is a reflex?

A reflex is an involuntary movement in response to a stimulus, occurring almost immediately after the stimulus.

What is the myotatic reflex?

The myotatic reflex is also known as the patellar reflex, patellar tendon reflex, or the knee-jerk reflex (knee jerk reflex).

People can develop a variety of central nervous system problems. Assessment of reflexes is an important part of the physical examination of a patient where a neurological disease is suspected. The knee reflex test is one of the most frequently performed neurological tests and is essential for identifying neuromuscular diseases (Salazar-Muñoz et al., 2019).

A monosynaptic stretch reflex

The myotatic reflex arc involves only two neurons, i.e. it is a monosynaptic reflex.

Within the reflex pathway, tapping the patellar ligament just below the patella stretches the quadriceps muscle. This stimulates sensory receptors in the muscle that trigger an impulse in a sensory axon. The sensory axon cell body lies in the dorsal root ganglion in the lumbar region of the spinal cord. The sensory axon synapses onto a motor neuron, which conducts the impulse to the quadriceps and triggers a contraction (the knee jerk reaction).

The myotatic reflex is a spinal reflex because the essential circuitry for this reflex is confined to the spinal cord; however, this information also passes to the brain.

Experimental Protocol

Here are the steps for setting up and running this classic experiment...

Related: Teach them a lesson they'll never forget! The Muscle Twitch Response experiment...

Step 1: Identify learning objectives

By the end of the activity students should be able to:

  • Elicit the myotatic reflex.
  • Describe the effect of the Jendrassik maneuver on the myotatic reflex.

Step 2: Set up your equipment to record signals

Flexible Teaching

This is a short lab with just one activity. We have designed it this way to allow flexible use of the lab. It could be used as a stand-alone activity, or be combined with other related labs such as the Hoffmann’s Reflex or Skeletal Muscle Function labs, found in the Lt Human Physiology Collection.


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