Redy Wireless Myotatic Reflex Sensor

Quick Answer: The Redy wireless myotatic reflex sensor is a data-logging sensor for studying the myotatic, or stretch, reflex, such as the knee-jerk response to a tap below the kneecap, with readings sent wirelessly for graphing. This myotatic reflex sensor is a teaching tool for physiology, not a neurological test instrument.

The Stretch Reflex in the Classroom

Tapping the tendon below the kneecap stretches the thigh muscle. Stretch receptors called muscle spindles send impulses along sensory neurons to the spinal cord, where they connect directly with motor neurons that make the same muscle contract, and the lower leg kicks. Because only one synapse is involved, this myotatic reflex is fast and happens without any conscious decision, which is exactly what physiology lessons set out to show.

A sensor lets students measure what they otherwise only watch: the time between the tap and the response, and how that response changes when the subject clenches their hands or is distracted. How this sensor detects the tap, the movement or the muscle activity is not described in the title. Reflex set-ups in teaching ranges vary between sensing hammers, motion or acceleration sensors, and surface electrodes, so the method and accessories need confirming before a practical is planned.

For another view of the nervous system at work, the wireless GSR sensor records skin conductance changes controlled by the sympathetic nervous system.

Specifications

Care & Handling

• Tap gently and only on the tendon; a hard tap is not needed and can hurt.
• Seat the subject so the lower leg hangs freely without touching the floor.
• Involve only willing participants, and stop if a student is uncomfortable.
• Clean any parts that touch the skin between students, as the maker directs.

Applications

• Measuring knee-jerk reflex latency
• Comparing reflex time with voluntary reaction time
• Showing the effect of reinforcement, such as clenching the hands, on the reflex
• Teaching the reflex arc with data gathered from the class

Why Choose LabEquip

Biology departments teaching the nervous system, and physiology courses in colleges, are the usual buyers. The sensor is offered by LabEquip within its chemistry lab equipment; detection method and accessories can be confirmed via the contact page.

Frequently Asked Questions

What is the myotatic reflex?

It is the stretch reflex: when a muscle is suddenly stretched, receptors inside it trigger a rapid contraction of the same muscle through a pathway in the spinal cord. The knee jerk is the most familiar example.

Why is the knee-jerk reflex so fast?

The pathway has only one synapse between the sensory and motor neurons, in the spinal cord. With so few connections, the signal returns to the muscle much sooner than a voluntary movement decided by the brain.

How is reflex time different from reaction time?

Reflex time is the delay of an automatic response that involves no conscious choice. Reaction time, such as catching a dropped ruler, involves the brain and is noticeably longer.

Can the sensor detect nerve problems?

No. It is a teaching sensor for demonstrating reflexes in class. It must not be used to assess anyone’s health, and differences in reflexes between students are normal.

Why does clenching the hands change the knee jerk?

Pulling clenched hands apart while the tendon is tapped, known as reinforcement, raises the excitability of the spinal motor neurons. The knee jerk often becomes stronger, which a logged response can show.

How should the leg be positioned?

Sit the subject on a bench high enough for the lower leg to hang freely and relaxed. Tension in the thigh muscle, or a foot resting on the floor, reduces the response.

Last Updated: September 2026