In the insulin sequence, what is the second event after glucose enters the bloodstream?

• A. Glucose enters the bloodstream
• B. Glycogen is stored in the liver
• C. Beta cells are stimulated to release insulin
• D. Insulin transports glucose to muscle cells

Answer: (C)

Rising blood glucose triggers the pancreatic beta cells to release insulin, making the secretion of insulin the immediate next event after glucose appears in the bloodstream. When glucose enters circulation, beta cells sense the rise and respond by releasing insulin into the bloodstream. That insulin then acts to move glucose into muscle and fat cells and to promote liver storage of glucose as glycogen. So the second step is the stimulation of beta cells to release insulin. The other options describe downstream effects: glycogen storage in the liver and insulin-facilitated glucose uptake into cells occur after insulin release, and the initial entry of glucose into the bloodstream is the first step.