Q: Give examples of how the human body maintains homeostasis when we exercise.

A: When we exercise the tissues of our body have an increased requirement for oxygen. The body facilitates this by increasing the respiratory and heart rate, thereby increasing the rate of gas exchange in the alveoli allowing more oxygen to bind with the Haem component of the red blood cells. Additionally, the volume of air inspired also increases with the help of accessory muscles and the inherent elasticity of lungs. The increase in heart rate leads to a greater speed of blood flow in the capillaries past the alveoli and therefore picks up oxygen at a much faster rate. There is an increase in cellular respiration and metabolism whilst we exercise which produces heat as a by-product. Thermoreceptors detect a marginal change in temperature and send neuronal messages to the hypothalamus in the brain. The hypothalamus then sends messages to cause peripheral vasodilation and increased sweating. The blood maintains its pH by increasing CO2 gas exchange at the alveoli and excreting other by products of exercise via the kidneys, e.g. Creatine released when muscle fibres are broken down during exercise is secreted by the body as creatinine in the urine.