Both the thymus and the pineal gland shrink after childhood.

A. Systolic pressure:The top number in a blood pressure reading represents systolic pressure. It reflects the maximum arterial pressure during ventricular contraction and indicates how forcefully the heart pumps blood into the arteries.

B. Pulse pressure:Pulse pressure is the difference between systolic and diastolic pressures. It is calculated from both numbers, not represented solely by the top number.

C. Mean arterial pressure:Mean arterial pressure (MAP) is the average arterial pressure during a cardiac cycle, calculated using both systolic and diastolic values. It is not indicated by the top number alone.

D. Diastolic pressure:Diastolic pressure is the bottom number in a blood pressure reading. It reflects the arterial pressure when the heart is relaxed, not the top number.

A. Insulin; lowers:Insulin is secreted by beta (β) cells in the pancreatic islets, primarily after meals when blood glucose is high. It lowers blood glucose by promoting uptake and storage, not during fasting periods.

B. Glucagon; raises:Alpha (α) cells secrete glucagon during fasting or many hours after a meal. Glucagon raises blood glucose by stimulating glycogenolysis and gluconeogenesis in the liver, ensuring a continuous supply of glucose for energy.

C. Glucagon; lowers:Glucagon does the opposite of lowering glucose; it elevates blood glucose levels to maintain homeostasis during periods of low glucose availability.

D. Insulin; raises:Insulin lowers, not raises, blood glucose levels. Secretion of insulin after meals promotes glucose storage in cells rather than increasing circulating glucose.

E. Glucocorticoids; raises:Glucocorticoids, such as cortisol, can increase blood glucose over time by promoting gluconeogenesis, but they are secreted by the adrenal cortex, not the pancreatic islets, and are not the primary hormone for immediate glucose regulation after fasting.