Fever may be a component of the nonspecific defense system. Body temperature is regulated by the hypothalamus, which contains a thermoregulatory control center (a "thermostat") that coordinates skeletal muscle shivering and the activity of the sympathoadrenal system to maintain body temperature at about 37° C. This thermostat is reset upward in response to a chemical called endogenous pyrogen. In at least some infections, the endogenous pyrogen has been identified as interleukin-1p, which is first produced as a cytokine by leukocytes and is then produced by the brain itself.
The cell wall of gram-negative bacteria contains endotoxin, a lipopolysaccharide that stimulates monocytes and macrophages to release various cytokines. These cytokines, including interleukin-1, interleukin-6, and tumor necrosis factor, act to produce fever, increased sleepiness, and a fall in the plasma iron concentration.
Although high fevers are definitely dangerous, a mild to moderate fever may be a beneficial response that aids recovery from bacterial infections. The fall in plasma iron concentrations that accompany a fever can inhibit bacterial activity and represents one possible benefit of a fever; others include increased activity of neutrophils and increased production of interferon.
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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.