Stretch reflex

Stretch Reflex

The Stretch Reflex (pronounced: /strɛtʃ rɪˈflɛks/), also known as the Myotatic Reflex, is a muscle contraction in response to stretching within the muscle. It is a monosynaptic reflex which provides automatic regulation of skeletal muscle length.

Etymology

The term "Stretch Reflex" is derived from the English words "stretch" and "reflex". "Stretch" comes from the Old English streccan, meaning "to stretch or extend", and "reflex" is derived from the Latin reflexus, meaning "bending back or reflection".

Mechanism

When a muscle lengthens, the muscle spindles are stretched and their nerve activity increases. This increase in activity is transmitted to the alpha motor neurons in the spinal cord, which causes the muscle fibers to contract and thus resist the stretching. A secondary set of neurons also sends signals to the opposing muscles (antagonists) to relax. This is known as reciprocal inhibition.

Clinical Significance

The stretch reflex has clinical significance in diagnosing nerve and muscle disorders. It is tested using a reflex hammer to strike the tendon and stretch the muscle, observing the contraction response. An absent or decreased response may indicate a problem with the peripheral nerves or muscle, while an exaggerated response may indicate a central nervous system disorder.

Related Terms

• Muscle spindle
• Alpha motor neuron
• Reciprocal inhibition
• Reflex hammer

External links

• Medical encyclopedia article on Stretch reflex
• Wikipedia's article - Stretch reflex

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