Question

Fasting a. Rise in insulin; rise in glucagon b. Fall in insulin; rise in glucagon c. Rise in insulin; fall in glucagon d. Fall in insulin; fall in glucagon

Short answer

During fasting, insulin levels fall to stop glucose uptake by cells, and glucagon levels rise to stimulate glucose production and glycogen breakdown. Thus, the correct answer is option b: Fall in insulin; rise in glucagon.

Step-by-step solution

Insulin Level During Fasting

As the blood sugar level drops during fasting, the body needs to stop promoting the uptake of glucose by cells. Insulin, which promotes this uptake, should decrease to adapt to this condition. Therefore, we can expect a fall in insulin levels during fasting.

Glucagon Level During Fasting

To maintain the blood sugar level during fasting, the body needs to increase the production of glucose as well as promote the breakdown of glycogen. Glucagon, which stimulates these processes, should increase during fasting. Therefore, we can expect a rise in glucagon levels.

Identify the Correct Option

Now that we know insulin levels fall and glucagon levels rise during fasting, we can match these changes with the given options: a. Rise in insulin; rise in glucagon --> Incorrect b. Fall in insulin; rise in glucagon --> Correct c. Rise in insulin; fall in glucagon --> Incorrect d. Fall in insulin; fall in glucagon --> Incorrect The correct answer is option b: Fall in insulin; rise in glucagon.

Key concepts

Insulin Regulation

During fasting, insulin regulation is crucial for maintaining energy balance. Insulin is a hormone that helps cells take in glucose from the blood, enabling them to produce energy. Insulin levels decrease during fasting to prevent cells from consuming glucose excessively.

Decreased insulin levels help to slow down the uptake of glucose by cells, preserving glucose in the bloodstream for vital organs like the brain. Without insulin regulation, blood sugar levels could drop too low, leading to hypoglycemia or low blood sugar, which can cause serious health issues.

It's important to remember that insulin is directly involved in the storage of nutrients. When fasting, the body shifts its focus from storing nutrients to mobilizing stored energy.

Glucagon Function

Glucagon plays a significant role in maintaining glucose levels, especially during fasting. It acts as a counter-regulatory hormone to insulin. While insulin helps lower blood sugar, glucagon works to increase it by signaling the liver to release glucose.

The primary function of glucagon is to stimulate the liver to convert stored glycogen into glucose, a process known as glycogenolysis. Increased glucagon levels ensure that the body has enough glucose available during fasting periods, preventing drastic drops in blood sugar.

By promoting the release of glucose into the bloodstream, glucagon helps maintain energy supply to organs, especially the brain, which relies heavily on glucose.

Blood Sugar Levels

Blood sugar levels, also called blood glucose levels, are tightly regulated by hormones like insulin and glucagon. During fasting, the body's glucose stores become critical. Blood sugar needs to stay within a healthy range to ensure proper bodily functions.

Low insulin levels help prevent a drop in blood sugar by limiting glucose uptake, while high glucagon levels prompt the liver to release glucose into the blood. This dual action provides a balanced supply of energy even when food intake is absent.

Monitoring blood sugar levels is essential, especially for individuals with metabolic disorders such as diabetes, where this balance is disrupted.

Glycogen Breakdown

Glycogen breakdown, or glycogenolysis, is a physiological process activated during fasting to maintain blood glucose levels. Glycogen is a stored form of glucose, primarily found in the liver and muscles.

In response to falling insulin and rising glucagon levels, the liver breaks down glycogen to release glucose into the bloodstream. This process ensures that the body continues to have a steady supply of glucose for energy, particularly for organs like the brain.

Glycogen breakdown is essential for sustaining metabolism during periods when food intake is limited, highlighting the body's capacity to adapt to varying energy needs.