Homeostatic mechanisms
Homeostatic control can change the PCO2 and hence the pH of the arterial plasma within a few seconds. The partial pressure of carbon dioxide in the arterial blood is monitored by the central chemoreceptors of the medulla oblongata. These chemoreceptors are sensitive to the levels of carbon dioxide and pH in the cerebrospinal fluid.The central chemoreceptors send their information to the respiratory centers in the medulla oblongata and pons of the brainstem. The respiratory centres then determine the average rate of ventilation of the alveoli of the lungs, to keep the PCO2 in the arterial blood constant. The respiratory center does so via motor neurons which activate the muscles of respiration (in particular, the diaphragm). A rise in the PCO2 in the arterial blood plasma above 5.3 kPa (40 mmHg) reflexly causes an increase in the rate and depth of breathing. Normal breathing is resumed when the partial pressure of carbon dioxide has returned to 5.3 kPa. The converse happens if the partial pressure of carbon dioxide falls below the normal range. Breathing may be temporally halted, or slowed down to allow carbon dioxide to accumulate once more in the lungs and arterial blood. The sensor for the plasma HCO−3 concentration is not known for certain. It is very probable that the renal tubular cells of the distal convoluted tubules are themselves sensitive to the pH of the plasma. The metabolism of these cells produces CO2, which is rapidly converted to H+ and HCO−3 through the action of carbonic anhydrase.
Treatment of the lymphocytic group of cicatricial alopecias (including lichen planopilaris, frontal fibrosing alopecia, central centrifugal alopecia, and pseudopelade (Brocq) involves use of anti-inflammatory medications. The goal of treatment is to decrease or eliminate the lymphocytic inflammatory cells that are attacking and destroying the hair follicle. Oral medications may include hydroxychloroquine, doxycycline, mycophenolate mofetil, cyclosporine, or corticosteroids. Topical medications may include corticosteroids, tacrolimus,  pimecrolimus, or Derma-Smoothe/FS scalp oil. Triamcinolone acetonide, a corticosteroid, may be injected into inflamed, symptomatic areas of the scalp. Treatment of the neutrophilic group of cicatricial alopecias (folliculitis decalvans, tufted folliculitis) is directed at eliminating the predominant pathogenic microbes that are invariably involved in the inflammatory process. Oral antibiotics are the mainstay of therapy, and topical antibiotics may be used to supplement the oral antibiotics. In dissecting cellulitis, pathogenic microbes are not usually present. Isotretinoin in small doses may be helpful in treating dissecting cellulitis.Treatment of the mixed group of cicatricial alopecias (folliculitis keloidalis) may include antimicrobials, isotretinoin, and anti-inflammatory medications. Patients are recommended to discuss any treatment with a dermatologist, who also explains potential side effects, as well as laboratory tests that are needed before starting treatment and sometimes are monitored during treatment. The course of cicatricial alopecia is usually prolonged. Treatment is continued until the symptoms and signs of scalp inflammation are controlled, and progression of the condition has been slowed.