ok moon bar i will answer them but just check if they r right 1. explain why blood pressure and heart rate differ when measuered in a reclining position and in a standing position. The reclining blood pressure and heart rate will be lower because the entire body is even with the heart and so the heart does not have to work against gravity to supply the body with blood. However, in a standing position, the circulatory system has to work against gravity to pump blood from the lower extremities of the body back to the heart and to pump blood up to the brain. 2. Explain why high blood pressure is a health concern. High blood pressure poses a high risk of stroke because the blood vessels are under more stress while moving blood. Therefore, a vessel under stress is more likely to burst possibly in the brain and cause a stroke. 3. Explain why an athlete must excerise harder or linger to acheive a maximum heart rate than a person who is not as physically fit. The dialation and constriction of blood vessels depends on the amount of muscle to transport blood. The muscle in athletes is normally bigger and stronger whichs helps to support blood vessels to transport blood around the body easier. Also he must have a higher rate of oxygen absorption and removal of carbon dioxide, if the rate does not get higher lactic acid will build up and cause muscle pain. 4. Explain why smoking causes a rise in blood pressure. The nicotine found in cigarettes causes a restriction in the blood vessels of the circulatory system. This restiction causes the blood vessels to become less flexible when moving the blood through the body.