Trace a homeostatic control pathway
Connect stimulus, receptor, coordination system, effector and negative feedback.
Section 14.1 · Homeostasis in mammals
A Level; Cambridge International Biology 9700, 2028–2030. Written answers are self-checked; this is not a practical skills certification.
Before you begin
- A control system detects a change, communicates information and changes an effector response.
Work on paper. Try each question before revealing help, and explain why your method works.
Quick readiness check
What makes a feedback response negative?
What you will learn
- Identify internal and external stimuli, receptors, coordination systems and effectors
- Explain how negative feedback opposes a change in a regulated variable
Build the explanation
A stimulus is a change detected by a receptor. Information is coordinated through the nervous system or endocrine system, leading an effector such as a muscle or gland to respond. In negative feedback, the response reduces the original deviation. When the variable moves back toward its range, the stimulus for that response becomes smaller.
Apply the limits
The receptor detects a change; the coordination system processes or transmits information; the effector produces a response. Negative feedback describes how the response affects the original change, not whether the response is harmful or simply 'negative'.
Pause and explain
In a feedback loop, a response reduces the stimulus that first triggered it. Explain why this is negative feedback.
Worked example
Arrange the parts of a response to rising body temperature.
Show the worked solution
- Thermoreceptors detect the rise.
- Coordination pathways signal effectors such as sweat glands.
- Sweating increases heat loss and opposes the rise.
Answer Stimulus → receptor → coordination system → effector → response that opposes the deviation.
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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.
A rise in blood glucose is followed by insulin secretion. Identify the stimulus, endocrine signal and response direction.
Give me a hint
Name the relevant structure or signal, then state its effect.
Compare my reasoning
- The rise in glucose is detected by pancreatic cells.
- Insulin is released and promotes glucose uptake or storage, lowering blood glucose toward its range.
The stimulus is raised blood glucose; insulin is the endocrine signal. Its effects lower blood glucose, opposing the initial rise.
Look for these in your work
- Correct mechanism
- Direction of response explained
A student calls muscle contraction a receptor in a control pathway. Correct the role.
Give me a hint
Separate the observed change from the body's response.
Compare my reasoning
- A receptor detects a stimulus.
- Muscle is an effector that carries out a response.
Muscle is an effector. A receptor detects the change and information is coordinated before the muscle responds.
Look for these in your work
- Evidence interpreted
- Control step identified
In a feedback loop, a response reduces the stimulus that first triggered it. Explain why this is negative feedback.
Give me a hint
Apply the mechanism to the new context without claiming more than the evidence shows.
Compare my reasoning
- Compare the response with the original deviation.
- The response reduces that deviation rather than reinforcing it.
It is negative feedback because the response opposes the original change, reducing the stimulus that triggered the pathway.
Look for these in your work
- New context applied
- Limits preserved
Common mistakes
- Calling the gland the receptor
- Describing negative feedback as making every variable fall
What can you explain now?
What makes a feedback response negative?
Compare with the explanation
It reduces the original deviation
The response opposes the change that initiated it.
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Make it stick
What are the main stages between a stimulus and a homeostatic response?
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.