Connect both branches of blood glucose regulation
Use opposing liver pathways around the same regulated concentration.
Section B13.3 · Homeostasis
Exam scope and assessment notes
Mapped to the named 0973 section using teaching from the corresponding single-science course. A 0973-specific review of every Core and Supplement objective is still in progress. Written practice is self-checked; it does not demonstrate supervised laboratory competence or award an official Cambridge grade. This qualification reports two grades on the 9–1 scale; confirm the entry route for your zone and exam series.
Before you begin
- Recall hormone production and blood transport, respiration, liver storage and electrical impulses along neurones.
Work on paper. Try each question before revealing help, and explain why your method works.
Quick readiness check
Which branch stores glucose in the liver?
What you will learn
- Compare high and low glucose control
- Close the feedback loop at the regulated level
Connect both branches of blood glucose regulation
Two opposing branches share a reference: insulin promotes storage after a rise; glucagon promotes release after a fall. Return reduces the stimulus. Original teaching model.
| Feature | Meaning |
|---|---|
| Above reference | Insulin; glucose → glycogen |
| Below reference | Glucagon; glycogen → glucose released |
| Shared organ | Liver responds; pancreas supplies signals |
| Loop closure | Departure reduces and corrective secretion diminishes |
Compare high and low glucose control
Blood glucose control has two opposing response branches in the required model. A rise stimulates increased pancreatic insulin secretion and liver glucose storage as glycogen. A fall stimulates increased pancreatic glucagon secretion and liver glycogen breakdown followed by glucose release. Both hormone signals travel in blood and both branches use the liver, but the chemical changes have opposite directions.
The set point is the supplied reference for deciding which departure has occurred. With an invented reference of 5 model units, a concentration of 7 requires downward correction and a concentration of 3 requires upward correction. The same reference is used for both comparisons; choosing a different reference after each reading would prevent a meaningful feedback explanation.
Close the feedback loop at the regulated level
The return towards the regulated level reduces the original stimulus for the increased corrective secretion. This closes each negative-feedback branch. Neither hormone is described as permanently maximal, and the target value is not presented as a clinical diagnostic threshold. Real biological regulation operates within suitable limits and is more complex than the paired teaching arrows.
Build a complete answer using condition, pancreatic hormone, liver reaction, blood effect and reduction of stimulus. The pancreas should not be replaced with the liver as hormone source. The liver storage and release reactions should not be interchanged. A final answer that merely lists insulin and glucagon has not yet explained their roles in maintaining the internal environment.
Sources for this lesson
Pause and explain
Which final link closes each feedback branch?
Worked example
Give both corrective branches around the supplied reference.
Show the worked solution
- Above reference: insulin promotes liver glucose → glycogen storage.
- Below reference: glucagon promotes liver glycogen → glucose release.
Answer Insulin lowers high blood glucose through liver storage; glucagon raises low blood glucose through liver breakdown and release. Return reduces the corresponding stimulus.
Try a topic test
Choose Easy, Normal or Difficult. Save your answers and open worked review after finishing.
Test this topic →From guided practice to a new situation
Write your answer and reasoning first. Use a hint only if you are stuck. The model solution is for self-checking; your written work is not automatically marked.
Complete both branches: high glucose → ___ → liver ___; low glucose → ___ → liver ___.
Give me a hint
Choose the hormone and reaction together.
Compare my reasoning
- High: insulin; glucose → glycogen storage.
- Low: glucagon; glycogen → glucose and blood release.
High: insulin; glucose → glycogen storage. Low: glucagon; glycogen → glucose and release into blood.
Look for these in your work
- Complete the high branch
- Complete the low branch
At supplied reference 5, predict the corrective hormone and concentration direction for 7 and 3 model units.
Give me a hint
Compare each reading with the same reference.
Compare my reasoning
- At 7, increased insulin contributes to a decrease.
- At 3, increased glucagon contributes to an increase.
7: insulin, concentration decreases. 3: glucagon, concentration increases, both towards reference 5.
Look for these in your work
- Use the shared reference
- Pair hormone and direction
Improve a diagram ending with concentration back near reference but unchanged maximal corrective secretion.
Give me a hint
Add the return-to-stimulus connection.
Compare my reasoning
- The initial departure has reduced.
- Increased corrective hormone secretion should diminish.
Add a feedback link: return towards the regulated level reduces the original stimulus and the increased corrective secretion.
Look for these in your work
- Identify the missing loop link
- Reduce the corrective response
Common mistakes
- Listing hormones without liver reactions.
- Using different reference levels for the two branches.
What can you explain now?
Which final link closes each feedback branch?
Compare with the explanation
Return reduces the original corrective stimulus
Response intensity is linked to the departure.
After trying it yourself, choose your next review. This is your self-assessment.
Your review choice appears on Today. Sign in to sync it across devices.
Make it stick
Explain both branches and the feedback link rather than listing hormone names alone.
If you needed the solution, close it and solve the problem again from a blank page. A correct answer is stronger when you can explain the reason for each step.