Answer to Question 1
Because fiber carries water out of the body, too much fiber can cause dehydration and intestinal discomfort. Also, iron is mainly absorbed early in the digestive process; thus, because fiber speeds the movement of foods through the digestive system, it may limit the opportunity for absorption of iron and other nutrients. Binders in some fibers link chemically with minerals such as calcium and zinc, making them unavailable for absorption and carrying them out of the body. Too much bulk from the diet could reduce the total amount of food consumed and cause deficiencies of both nutrients and energy. The malnourished, some older adults, and children, because they eat small amounts of food anyway, are especially vulnerable to these concerns.
Answer to Question 2
When the blood glucose level rises, the body adjusts by storing the excess. The first organ to detect the excess glucose is the pancreas, which releases the hormone insulin in response. Most of the body's cells respond to insulin by taking up glucose from the blood to make glycogen or fat. Thus, the blood glucose level is quickly brought back down to normal as the body stores the excess. Insulin's opposing hormone, released by the pancreas when blood glucose is too low, is glucagon, which draws forth glucose from storage, making it available to supply energy. Insulin and glucagon both work to maintain the concentration of glucose in the blood within the normal rangeneither too high nor too low.
Natural Hazards
Early in the twentieth century, when malnutrition was common, companies such as this one advertised
Movement of Sodium and Potassium Ions During the Action Potential
Resting Membrane Potential: Voltage Difference
Action Potential in a Ventricular Fiber