Deep somatic pain

As its name implies, deep somatic pain is generated in deep body structures, such as the periosteum, muscles, tendons, joints, and blood vessels. This type of pain is more diffuse than cutaneous pain. It may be elicited by strong pressure, ischemia, and tissue damage.

Tissue ischemia. When blood flow to a tissue is decreased or interrupted, the tissue becomes painful within a few minutes. In fact, the greater the rate of metabolism in the tissue, the more rapid is the onset of pain. The causes of pain due to tissue ischemia include:

• Accumulation of lactic acid due to the anaerobic metabolism that occurs during ischemia

• Release and activation of noxious chemicals in the area of tissue ischemia due to tissue damage (see Table 8.1)

The lactic acid and other noxious chemicals stimulate polymodal nocicep-tors.

Muscle spasm. The pain induced by muscle spasm results partially from the direct effect of tissue distortion on mechanical nociceptors. Muscle spasm also causes tissue ischemia. The increased muscle tension compresses blood vessels and decreases blood flow. Furthermore, the increased rate of metabolism associated with the spasm exacerbates the ischemia. As discussed earlier, ischemia leads to stimulation of polymodal nociceptors.

Essentials of Human Physiology

Essentials of Human Physiology

This ebook provides an introductory explanation of the workings of the human body, with an effort to draw connections between the body systems and explain their interdependencies. A framework for the book is homeostasis and how the body maintains balance within each system. This is intended as a first introduction to physiology for a college-level course.

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