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Principles of Manual Medicine

Reflex Activity

In addition to the overlap of visceral afferents onto spinal pathways that receive somatic efferents, there also exists an overlap of visceral afferents onto spinal pathways that receive somatic afferents, resulting in the sensory experience of referred pain in segmentally related structures. This means that abnormal afferent activity from a structure such as the heart may be passed to segmentally related somatic efferents and segmentally related somatic afferents through viscero-somatic reflex arcs located in the spinal cord. A common example of this would be the shoulder pain and muscle tension associated with acute myocardial infarction. Nociceptive activity from the compromised myocardium is experience as referred pain in the shoulder and/or chest, and is accompanied by increased muscle tension. Unfortunately, it is possible for a vicious cycle of increased sympathetic activity to occur. Increased sympathetic tone from these painful shoulder muscles may result in increased sympathetic outflow back to the cardiovascular system, resulting in vasoconstriction and an increase in cardiac workload, with an increase in myocardial irritation. Manipulative treatment of somatic structures can be used to reduce sympathetic activity back to the affected viscus, thus breaking the cycle and helping to relieve the pain and tension in the facilitated segment.

Some common examples of how dysfunction in visceral structures and somatic structures can adversely influence the functionality of visceral and somatic structures that are segmentally related are listed below:

  • Somato-somatic reflex - occurs when somatic stimuli produce patterns of reflex activity in segmentally related somatic structures. For example, neurons in the spinal cord may receive abnormal levels of afferent activity from muscle spindles as a result of injury. Segmentally related somatic fibers may then stimulate muscles fibers resulting in tightness and pain.

  • Viscero-cutaneous reflex --- occurs when localized visceral stimuli produce patterns of reflex activity in segmentally related visceral structures. For example, preganglionic autonomic neurons in the spinal cord may receive afferent activity from the intestines as a result of intestinal gastritis. Segmentally related postganglionic fibers in the sympathetic trunk may then stimulate cutaneous receptors resulting in dilation of blood vessels and reddening of the skin.

  • Viscero-somatic reflex - occurs when localized visceral stimuli produce patterns of reflex activity in segmentally related somatic structures. For example, preganglionic autonomic neurons in the spinal cord may receive afferent activity from the intestines as a result of intestinal gastritis. Segmentally related somatic fibers may then stimulate abdominal muscles fibers resulting in tightness and pain.

  • Cutaneo-visceral reflex -- occurs when localized cutaneous stimuli produce patterns of reflex activity in segmentally related visceral structures. For example, preganglionic autonomic neurons in the spinal cord may receive afferent activity from cutaneous thermoreceptors. Segmentally related postganglionic fibers in abdominal ganglia may then inhibit intestinal motion caused by pathology such as gastritis, reducing pain caused by convulsive contractions.

  • Viscero-visceral reflex -- occurs when localized visceral stimuli produce patterns of reflex activity in segmentally related visceral structures. to view a simplified example of a viscero-visceral reflex). For example, preganglionic autonomic neurons in the spinal cord may receive afferent activity from the viscera. They may excite postganglionic autonomic neurons (sympathetic efferents) which may result in an undesirable immobilization of the intestines following surgery.

In summary, it is essential for the osteopathic physician to understand and have committed to memory the somatic regions that are likely to be affected by viscero-somatic reflexes resulting from visceral pathology. Manipulative treatment may then be used to reduce somato-sympathetic activity from associated facilitated structures back to the affected viscus.

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