OCR General Certificate of Secondary Education (GCSE) Biology Practice Exam

What internal environments must remain steady in the body?

1. Blood pressure and heart rate

2. Blood glucose concentration, water content, body temperature

3. Muscle tone and mental focus

4. Body mass and fat distribution

The correct answer is: Blood glucose concentration, water content, body temperature

The internal environments that must remain steady in the body relate to vital physiological processes that ensure homeostasis. Blood glucose concentration, water content, and body temperature are all critical parameters that the body regulates to maintain optimal functioning. Blood glucose concentration is essential for providing energy to cells, particularly in the brain and muscles. It must remain within a narrow range to prevent conditions such as hypoglycemia or hyperglycemia, which can have significant health consequences. Water content in the body is also crucial as it affects cell function, nutrient transport, and waste removal. The body has mechanisms like sweating, urination, and thirst to regulate water balance effectively. Body temperature is vital for metabolic reactions to occur at the right pace. Enzymes and other biochemical processes are temperature-sensitive, and maintaining a stable body temperature (around 37°C) is essential for sustaining life. While blood pressure and heart rate, muscle tone, mental focus, body mass, and fat distribution are important for overall health, they do not have the immediate and direct impact on homeostasis that the options related to blood glucose, water content, and body temperature do. Therefore, the regulation of these three factors is fundamental for the body to function properly.