Which physiological response is characterized by a decrease in tissue size due to reduced demand?

• A. Hypertrophy
• B. Hyperplasia
• C. Atrophy
• D. Metaplasia

Answer: (C)

The physiological response characterized by a decrease in tissue size due to reduced demand is atrophy. Atrophy occurs when cells decrease in size and number, often due to a lack of use, reduced workload, diminished blood supply, inadequate nutrition, or other factors that lead to decreased functional demands on the tissue. This process can be seen in various scenarios, such as muscle atrophy in individuals who are bedridden or have a sedentary lifestyle, where the lack of physical activity leads to a reduction in muscle mass over time.

In contrast, hypertrophy involves an increase in cell size in response to increased demand, such as in the case of resistance training, where muscles grow larger to accommodate heavier loads. Hyperplasia refers to an increase in the number of cells within a tissue, often as a compensatory response to increased physiological demands or hormonal stimulation. Metaplasia is the process where one differentiated cell type is replaced by another, often as a response to chronic irritation or inflammation. Understanding these distinctions helps clarify why atrophy is the correct response to the question regarding reduced demand.