A spinal reflex is a rapid, involuntary response to a stimulus that is mediated primarily by the spinal cord, without involvement of the brain. Stretch and inverse stretch reflexes are two types of spinal reflexes. Although both these reflexes are ipsilateral, there are several differences between them.
The difference between stretch and inverse stretch reflex lies in their responses to muscle stretch. Stretch reflex is a muscle contraction that occurs in response to stretching in the muscles, while inverse stretch reflex is an inhibitory effect on the muscle, resulting from the muscle tension stimulated by the sensory receptor of the muscle.
CONTENTS
1. Overview and Key Difference
2. What is a Stretch Reflex
3. What is an Inverse Stretch Reflex
4. Similarities Between Stretch and Inverse Stretch Reflex
5. Stretch vs Inverse Stretch Reflex in Tabular Form
6. Summary – Stretch vs Inverse Stretch Reflex
7. FAQ – Stretch and Inverse Stretch Reflex
What is a Stretch Reflex?
Stretch reflex is also known as a myotatic reflex. It is a muscle contraction in response to stretching within the muscle. The stretch reflex has the shortest latency of all spinal reflexes. Moreover, the stretch reflex is a monosynaptic reflex and normally provides automatic regulation of skeletal muscle length.
Generally, when a muscle lengthens, the muscle spindle is stretched. This increases the nerve activity, ultimately increasing alpha motor neuron activity. This causes the muscle fibers to contract and resist stretching. Furthermore, in this mechanism, a secondary set of neurons causes the opposing muscle to relax. The function of this reflex is to maintain the muscle at a constant length.
What is an Inverse Stretch Reflex?
Inverse stretch reflex is mediated by the Golgi tendon organs or specialized muscle receptors. It is also known as autogenic inhibition. When these Golgi tendon organs are stimulated by a prolonged stretch, this causes the stretched muscle to relax. Sometimes, this reflex is also called the inverse myotatic reflex, as it is the inverse of the stretch reflex. The inverse stretch reflex is polysynaptic.
The inverse stretch reflex is a normal component of the reflex arc of the peripheral nervous system. Moreover, the inverse stretch reflex is less sensitive than the stretch reflex. Furthermore, like the stretch reflex, the tendon reflex is also ipsilateral.
Similarities Between Stretch and Inverse Stretch Reflex
- Stretch and inverse stretch reflexes are two different spinal reflexes.
- The inverse stretch reflex is the inverse of the stretch reflex.
- Both these are ipsilateral.
- Both these perform protective functions.
Difference Between Stretch and Inverse Stretch Reflex
Definition
a. The stretch reflex operates as a feedback mechanism to control muscle length by causing muscle contraction.
b. The inverse stretch reflex operates as a negative feedback mechanism to control muscle tension.
Monosynaptic/Polysynaptic
a. The stretch reflex is monosynaptic.
b. The inverse stretch reflex is polysynaptic.
Latency
a. The stretch reflex has the shortest latency.
b. The inverse stretch reflex has a longer latency.
Sensitivity
a. The stretch reflex is more sensitive.
b. The inverse stretch reflex is less sensitive.
Controlled by
a. The stretch reflex is controlled by alpha and gamma motor neuron activity.
b. The inverse stretch reflex is controlled by Golgi tendon organs or specialized muscle receptors.
Function
a. The stretch reflex functions to maintain the muscle at a constant length.
b. The inverse stretch reflex functions to prevent tendons from tearing due to muscle tension.
The infographic below presents the differences between stretch and inverse stretch reflex in tabular form for side-by-side comparison.
Summary – Stretch vs Inverse Stretch Reflex
Stretch and inverse stretch reflexes are two different spinal reflexes. Stretch reflex operates as a feedback mechanism to control muscle length by causing muscle contraction while inverse stretch reflex operates as a negative feedback mechanism to control muscle tension. Thus, this summarizes the difference between stretch and inverse stretch reflex.
FAQ: Stretch and Inverse Stretch Reflex
1. What happens to cause a stretch reflex?
- The stretch reflex operates as a feedback mechanism to control muscle length by causing muscle contraction. The stretch reflex is a monosynaptic reflex that originates in the muscle spindles with any stimulus. This reflex travels through an afferent pathway to the spinal cord, where it synapses with the corresponding alpha motor neuron. Ultimately, this contracts the muscle fibers where it has produced the stimulus.
2. What is a stretch reflex example?
- A sudden stretch like tapping the Achilles tendon is an example of a stretch reflex. This particular reflex causes a contraction in the soleus-gastrocnemius group of muscles. The patellar reflex is another example of a stretch reflex.
3. How long does the stretch reflex last?
- A study by Wilson (1990) discovered that while bench pressing, a stretch reflex would last up to four seconds. At that point, all stored elastic energy is lost. Thus, it has the shortest latency among all other spinal reflexes.
4. What is the inverse stretch reflex?
- The inverse stretch reflex is mediated by the Golgi tendon organs or specialized muscle receptors. It is also known as autogenic inhibition. The inverse stretch reflex operates as a negative feedback mechanism to control muscle tension.
5. What is a polysynaptic reflex?
- In contrast to a monosynaptic reflex, a polysynaptic reflex is mediated through at least two synapses and one interneuron. An example is the automatic withdrawal of the leg when the footsteps on a sharp object.
Reference:
1. “Stretch Reflexes.” Current Biology – Cell.com
2. “Stretch Reflex & Golgi Tendon Reflex.”KusumSC.
Image Courtesy:
1. “Patellar tendon reflex arc” By Amiya Sarkar – Own work (CC BY-SA 4.0) via Commons Wikimedia