Question

The body goes through absorptive and postabsorptive states throughout the course of 24 hours, as illustrated in Figure 25-11 in your textbook. The nutrient pools (glucose, amino acid, and fatty acid) illustrated in Figure 25-1 vary in size during these states as the body absorbs these nutrients from food, uses them for energy production, puts them into or releases them from storage, or builds/breaks down body structure.The body has multiple hormonally-driven mechanisms by which to maintain a relatively constant glucose pool in order to ensure that adequate glucose is always available for the brain.  Neurons rely almost exclusively on glucose and cannot use fatty acids or amino acids as an alternate source.

The mass balance equation can be applied to the glucose pool.  Recall that the equation states that in order to maintain balance of a particular substance, the intake of that substance + its metabolic production must equal excretion of that substance + metabolic removal of that substance.

Intake + metabolic production = Excretion + metabolic removal

1. Your first task is to apply the mass balance equation to the maintenance of the glucose pool during the absorptive and postabsorptive states.  

For each state, you need to explain how each of the parts of the equation contribute to increases/decreases in the glucose pool, and the internal mechanisms that are employed to counteract those changes to restore balance. As part of your explanation, you need to include the specific organs/tissues, hormones, and metabolic processes that are involved.  For each hormone, include what leads to its release, cell types it targets, and what it stimulates the targets to do.

2. Your second task is to apply the mass balance equation to the regulation of blood glucose, or lack thereof, in someone who suffers from diabetes mellitus.   Describe what part(s) of the equation are not functioning properly.  Uncontrolled diabetes mellitus is associated with a number of classic symptoms:  excessive hunger and thirst, weight loss, and excessive urination.  Explain these symptoms by applying the mass balance equation, absorptive vs. postabsorptive states, and nutrient pools.

Answer 1

ANSWER 1

When we eat food , the body uses the energy released to fuel the cells.

The ABSORPTIVE STATE of the body lasts for four hours during and after each meal. In this state the digested food is converted into sugar or glucose. The ingestion of food and rise of glucose concentration in blood stimulates pancreatic beta cells to release INSULIN into the blood stream. Insulin is the main hormone in this state that allows the glucose to enter the cells and be used for energy.The LIVER will store glucose and converts it into glucose -6- phosphate , by doing this a concentration gradient is established where glucose concentration in the blood is greater than that in the cells and this leads to the continuous moving of glucose from blood to the cells where they are required . Insulin also stimulate storage of glucose as glycogen in skeletal muscle and liver cells. Muscle protein can be catabolised and can be used as fuel at times of starvation . Glucose is ultimately released from liver into the blood stream through a series of processes to maintain the normal blood glucose levels .

The POSTABSORPTIVE STATE or fasting state occurs when food has been digested , absorbed and stored. Body rely on initially stored glycogen.Glucose levels drop, and in response to that insulin levels also drop. But to meet the demands of tissues and cells the blood glucose levels should be maintained in normal range .Hormone GLUCAGON is released from alpha cells of pancreas . It acts on liver cells and inhibits the synthesis of glycogen and stimulates the breakdown of stored glycogen back into glucose , as a result blood glucose levels begin to rise.

ANSWER 2

INSULIN is the most important hormone governing metabolism.

In Diabetes cells becomes less sensitive to insulin , leading to hyperglycemia .Large and prolonged rise in glucose produces the renal effect of osmotic diuresis , Polyuria, dehydration , hypovolemia.

In the ABSORPTIVE STATE glucose is abundant , main fuel of the body , excess is stored.These process are driven by insulin.

In POSTABSORPTIVE states , Glucose level reduces, insulin secretion ceases and stored glucose ,fatty acids and ketones

are released into blood to provide fuel to the body . In Diabetes the situation is that the body tends to remain in postabsorptive state due to lack of insulin . So the main disturbance in diabetes is metabolic.