In the sequence describing how insulin affects blood glucose, which event occurs first?

In the sequence describing how insulin affects blood glucose, which event occurs first?

• A. Beta cells are stimulated to release insulin
• B. Glucose enters the bloodstream
• C. Glycogen is stored in the liver
• D. Glycogen is converted to glucose by alpha cells

Answer: (B)

Glucose entering the bloodstream is the initial event after a meal. This rise in blood glucose signals the pancreatic beta cells to release insulin, which then promotes uptake of glucose by tissues and storage as glycogen in the liver. Glycogen storage occurs after insulin is present, not before. The other processes—beta-cell stimulation, glycogen storage, or glycogen breakdown by alpha cells—occur subsequently or under different conditions, such as low blood glucose. So, the first step in the insulin–glucose sequence is glucose entering the bloodstream.

Glucose entering the bloodstream is the initial event after a meal. This rise in blood glucose signals the pancreatic beta cells to release insulin, which then promotes uptake of glucose by tissues and storage as glycogen in the liver. Glycogen storage occurs after insulin is present, not before. The other processes—beta-cell stimulation, glycogen storage, or glycogen breakdown by alpha cells—occur subsequently or under different conditions, such as low blood glucose. So, the first step in the insulin–glucose sequence is glucose entering the bloodstream.