During exercise, sensory receptors detect changes in oxygen and carbon dioxide levels in the blood. this information is then sent to the brain's medulla, which causes the heart to beat faster and increases the rate of breathing. exercising also causes the nervous system to signal the pancreas and thyroid gland to release hormones which regulate metabolism. which statement is best demonstrated by this scenario? a. exercise is important for the body to function properly. b. increased heart rate and blood flow decrease oxygen supply. c. nerves transmit and respond to every major system in the body. d. hormones act as signal molecules between all body systems.

ANSWER: A. Exercise is important for the body to function properly.

Exercise  deliver adequate amounts of oxygen and remove waste from body tissues by regulating nervous, respiratory, circulatory and hormonal systems in the body. During exercise, body tissues and other metabolic processes in the body requires oxygen.Low levels of oxygen and higher levels of carbon dioxides are mainly detected by sympathetic division of the autonomic nervous system which control the physical activity of the body by increasing heart rate, blood pressure and respiration  as a result of this there is an increase in the amount of blood pumped per minute by the heart and oxygenated body gets distributed to the tissues. This also involves release of glucose by the liver as an energy reservoir to control the level of blood glucose pancreas secrete insulin hormone , thyroid gland is also stimulated in response to increase heart rate.

affects the water bodies: excessive use of fertilizers causes eutrophication. the fertilizers which are used on plants affect the quality of land on which it is used, further causing erosion of soil. the fertilizers used on plants contain harmful chemical fumes which affect the environment.