Physiology is the study of function in living systems; thus, physiological changes are changes that occur within an organism, whether at the level of organism, organ system, organ, tissue, cell or organelle. Physiological changes occur from a number of causes and factors. Common physiological changes are those that take place due to aging and pregnancy.
Physiological changes include changes in the physical, bioelectrical, biochemical and mechanical functions of an organism. In all organisms, significant physiological changes occur due to aging. In humans, blood pressure increases, cardiac output decreases, lungs develop impaired gas exchange and expiratory flow rates slow down. Age also brings atrophication of the epidermis, elevated blood glucose and a decline in lean body mass.
Pregnancy also brings a number of physiological changes for both mother and child. Women's bodies change in preparation for child birth and nursing. This leads to symptoms like frequent urination, heartburn, fatigue, sleep disturbances, hemorrhoids, cramps and darkening of the skin.
There are also physiological disorders, conditions in which the vital functions of an organism are debilitated. Physiological disorders are often the result of environmental factors, pathogens and nutrient deficiencies. Such disorders impair growth, mobility, respiration, nutrition and mental activities. Ultimately, they may lead to death.