Brain-Based Solutions™ for the Flexor
Withdrawal Reflex

A Physiological Protective Response (Part 3 of 5)

 

Introduction

 

The nociceptive or flexor withdrawal reflex (FWR) is a cord-mediated reflex intended to protect the body from damaging stimuli.

The classic example is the reflexive response of the offended part after touching something hot, and withdrawing that body part from the hot object. The heat, for example, stimulates noxious receptors in the skin, triggering the primary afferents that travel to the cord and brain.

The sensory input synapses ipsilaterally in the cord’s gray matter and ultimately the anterior horn cells with facilitation of the associated physiological flexors that cause withdrawal; other neurons cause facilitation of the contralaterally related and associated physiological extensors, pushing away from the stimulus.

There is also a simultaneous and reciprocal contralateral response—a crossed cord reflex (part 4 of 5). Other interneurons instantaneously relay the sensory information up to the cerebellum, midbrain, and cortex to integrate the nociceptive response and the consequential protective movement.

 

The Reflex

 

All human physiological reflexes have a predictable display. Therefore, either they work according to their original design or they are pathological. There are no other choices. If a reflex displays itself in ways other than according to its pre-programmed format it can be considered “other-than-human,” with a concomitant increased the risk of injury. Reflex error always requires treatment.

​

 

 

 

 

 

 

​

 

​
 

​

​​

​

​Mechanism of Display

​

The FWR is the manifestation of a painful (i.e., nociceptive) stimulus. As a result, the limb protects itself and the rest of the body—a survival response—by withdrawal. (In this case, we will only focus on lower extremity’s response to nociception, but there is also an upper body response, as well.)

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

​

proximal rectus femoris contralaterally; this is opposite of what one would expect. (For more about the influence on the proximal and distal aspects of the bi- or multi- articular muscle, see the “Spinal Pattern Generator” videos from HealthBuilderS.com)

 

The results of the entire neurological examination indicated that Michael was deafferentated through his cervicodorsal spine and left shoulder girdle and he was not ventilating properly, affecting his left cerebellum.

The Fix

 

Coupled chiropractic manual manipulation of Michael’s left cervicodorsal spine and left shoulder girdle, together with certain specific physiological exercises to rehabilitate the structure and nervous system in order to normalize his FWR.

The Result

 

According to Michael’s original diagnosis, increasing the afferentation to his left cerebellum normalized his flexor withdrawal response. Now, stroking the sole of his foot with a sharp object caused the proper physiological response—the facilitation of the proximal ipsilateral rectus femoris and the inhibition of the proximal rectus femoris contralaterally. This response is more human-like.

Summary

 

This erroneous FWR display is significant. It suggests that a painful (nociceptive) stimulus to either of Michael’s feet might (figuratively) cause him to collapse onto the stimulus (discussed in the “Spinal Pattern Generator” videos). The examination indicated that his nervous system was originally unable to update fast enough to maintain upright posture. Actually, if Michael were to receive a stimulus that was significant enough to maintain his capacity for upright posture, his lower body flexors would inhibit increasing his probability of falling. Michael had other therapies and left the office able to respond nominally.

​