pHhomeostas

pHhomeostas, commonly referred to as pH homeostasis, describes the physiological processes by which organisms maintain the hydrogen ion concentration of body fluids within a narrow, optimal range. This regulation is essential for enzyme activity, protein structure, and overall cellular function. In humans, arterial blood pH is typically kept around 7.35 to 7.45.

The regulation of pHhomeostas relies on three interlocking components: chemical buffering, respiratory control, and renal regulation. Buffers such as the bicarbonate–carbonic acid pair, phosphate buffers, and various proteins provide immediate, though temporary, resistance to pH changes. The respiratory system modulates pH by controlling carbon dioxide levels through ventilation; CO2 + H2O ⇌ H2CO3 ⇌ H+ + HCO3−. Increased ventilation lowers CO2 and can raise pH, while reduced ventilation raises CO2 and lowers pH. The kidneys adjust long-term pH by reabsorbing or excreting bicarbonate, secreting hydrogen ions, and producing ammonium; these adjustments occur over hours to days.

Regulatory mechanisms integrate signals from central and peripheral chemoreceptors. Central chemoreceptors respond mainly to changes in CSF pH linked to CO2, while peripheral chemoreceptors detect blood pH andCO2, modulating respiration. Hormonal and neural pathways influence renal and ventilatory responses according to metabolic needs and stress.

Disorders of pHhomeostas include acidosis and alkalosis, each with respiratory and metabolic subtypes, often involving compensatory mechanisms. Clinical assessment commonly uses arterial blood gas measurement (pH, PCO2, HCO3−) and urine analysis to determine the underlying disturbance and the body’s compensatory response.