Question

when blood sugar rises after a meal, the pancreas releases insulin. this causes cells to take up excess glucose. when blood sugar falls, glucagon is released from the pancreas. this causes cells to break down glycogen into glucose, which is then released into the blood. which of the following aspects of this system best explains why it is an example of homeostasis?
a the release of insulin causes blood sugar levels to fall.
b the release of glucagon causes blood sugar levels to rise.
c the pancreas and liver work together as an organ system.
d the system works to keep blood sugar levels within a narrow range.
e insulin and glucagon are enzymes that only work within a narrow range of temperatures.
question 14
the semilunar valves:
a prevent arterial blood from reentering the ventricles
b prevent blood from reentering the atria when ventricles contract
c prevent the back flow of blood in large veins

Explanation:

For the first question: Homeostasis refers to maintaining stable internal conditions within a narrow range. Insulin lowers high blood sugar, glucagon raises low blood sugar—together, they keep levels stable, which matches option D. Options A/B describe single actions, C is incorrect (pancreas/liver aren’t an organ system), E is false (they’re hormones, not enzymes). For the second question: Semilunar valves (aortic/pulmonary) are between ventricles and arteries, preventing arterial blood from flowing back into ventricles when ventricles relax. Option B refers to atrioventricular valves, C to vein valves.

Answer:

First question: D. The system works to keep blood sugar levels within a narrow range.
Second question: A. Prevent arterial blood from reentering the ventricles