Hormone feedback loop
About this app
A model day in a body diagram: drag a meal, a sugar drink or exercise into the day and follow blood glucose, insulin and glucagon. A bar shows where the glucose of a meal ends up. Assign the control loop, open the feedback and compare type 1 and type 2 diabetes as models. School biology, not medical advice.
With explain mode: an AI tutor walks you through the app, points out what matters in the scene and answers your questions.
What it is about
Blood glucose is a controlled variable. The islet cells of the pancreas measure the glucose concentration in the blood. Beta cells release insulin when it is high, alpha cells release glucagon when it is low. The two hormones act as antagonists and oppose the deviation: negative feedback. Insulin is a signal. In muscle and fat cells transporters reach the membrane, glucose flows in, and liver and muscle build glycogen. Glucose is broken down by the cells themselves, in cellular respiration. Glucagon acts on the liver, which breaks down glycogen, forms new glucose and releases it into the blood.
What the app shows
A body diagram shows the bloodstream, gut, liver, pancreas, brain, fat cell and muscle cell, plus the kidney once the value exceeds the renal threshold. Next to it runs the glucose curve of a model day from 6 am to midnight with insulin and glucagon tracks. A bar follows the glucose of one meal through gut, blood, liver, muscle and fat to respiration and urine. The total stays the same. Type 1 and type 2 diabetes are school models with model values. The app is not medical advice and names no therapy.
What you can try
Drag a meal, a sugar drink or exercise into the day and watch the curve. Move markers or drag them out again. Compare fasting, exercise, type 1 and type 2 with the dashed curve of a healthy day. In the control loop, assign set point, actual value, sensor, controller, effector and disturbance, then open the feedback: the hormones stay at the fasting level and the value leaves the band. Seven questions, some as predictions with the day hidden, give reasoned feedback.
Frequently asked questions
- Does insulin break down sugar?
- No. Insulin is a signal. It makes muscle and fat cells take up glucose and makes liver and muscle store it as glycogen. Glucose is broken down by the cells themselves, in cellular respiration.
- How does the blood glucose feedback loop work?
- The controlled variable is the glucose concentration in the blood, with a set point of about 90 mg/dl. Islet cells measure the value and release insulin or glucagon. Muscle and fat cells take up glucose, and the liver takes it up or releases it. The response opposes the deviation: negative feedback.
- What is the difference between type 1 and type 2 diabetes?
- In type 1 the beta cells are destroyed and insulin is missing. In type 2 the target cells respond less to insulin (insulin resistance), and secretion often declines later. Above the renal threshold of about 180 mg/dl, glucose appears in the urine.
- Are the numbers in the app measurements?
- No. All numbers are model values for a school experiment, calculated with a simplified model. Type 1 is calculated without insulin treatment. The app is school biology and gives no recommendations for your own health.
Subject: Biology (Gymnasium)
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