Describe a hormone and trace its blood-borne route
Connect chemical substance, gland, blood and specific target organs.
Core and Extended; Biology 0610, 2026–2028. Use the stated specimen features and evidence. Diagrams are schematic. Written practice is self-checked
Before you begin
- Recall electrical impulses, blood transport, gland secretion and the distinction between a stimulus and a body response.
Work on paper. Try each question before revealing help, and explain why your method works.
Quick readiness check
What carries a hormone around the body?
What you will learn
- Follow the source and transport route
- Explain the specific target response
Describe a hormone and trace its blood-borne route
| Feature | Meaning |
|---|---|
| Source | Hormone-producing gland |
| Signal | Chemical substance |
| Transport | Blood circulation |
| Response | Altered activity of one or more specific target organs |
Follow the source and transport route
A hormone is a chemical substance made by a gland. The gland releases the hormone into the blood, which carries it through the circulation. At one or more specific target organs, the hormone changes activity. A complete description therefore includes the type of signal, its source, its transport and its effect; simply saying it is a messenger misses important parts.
The producing gland and the responding target are different roles. For example, adrenal glands produce adrenaline, while the heart can respond by beating faster. The chemical substance is the hormone; the heart is not the hormone, and a blood vessel is a transport route rather than automatically a responding target. Name each role before joining the steps into a sentence.
Explain the specific target response
Blood can deliver a hormone to many parts of the body without every organ responding in the same way. Specific target cells can recognise the relevant hormone and change their activity. Receptors provide useful background for this specificity, but the required description here concerns one or more specific target organs rather than detailed receptor chemistry.
Contrast this route with an electrical impulse travelling along a neurone. A hormone is carried as a chemical substance by blood; it does not travel down an axon as an electrical impulse. In a supplied pathway, use the arrows to trace gland production, blood carriage and target action, and avoid swapping the source with the responding organ.
Pause and explain
Which description includes all four required parts?
Worked example
Trace adrenaline from production to a heart response.
Show the worked solution
- Adrenal glands produce the chemical hormone adrenaline.
- Blood carries it to the heart, a target whose activity changes.
Answer Adrenal glands → adrenaline carried by blood → increased heart activity.
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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.
Describe a hormone using its type, source, transport and effect.
Give me a hint
Build the four links in order.
Compare my reasoning
- It is a chemical substance produced by a gland.
- It is carried by blood and changes activity of specific target organs.
A hormone is a chemical substance produced by a gland, carried by the blood, which alters activity of one or more specific target organs.
Look for these in your work
- Include chemical and gland
- Include blood and specific target activity
In a model, gland X releases chemical Y; blood carries Y to organ Z, whose activity changes. Assign the three roles.
Give me a hint
Separate producer, substance and responder.
Compare my reasoning
- X is the producing gland and Y the hormone.
- Z is a specific target organ.
X: producing gland; Y: hormone; Z: specific target organ. Blood supplies the transport route.
Look for these in your work
- Identify all three roles
- Keep transport distinct
Correct: adrenaline is an electrical impulse carried from the heart along an axon.
Give me a hint
Use the source and transport already learned.
Compare my reasoning
- Adrenal glands produce adrenaline as a chemical hormone.
- Blood carries it to specific targets such as the heart.
Adrenaline is a chemical hormone produced by adrenal glands and carried by blood to specific target organs, including the heart.
Look for these in your work
- Correct signal and source
- Correct transport and target
Common mistakes
- Calling the gland itself a hormone.
- Replacing blood carriage with an electrical impulse along an axon.
What can you explain now?
Which description includes all four required parts?
Compare with the explanation
A gland produces a chemical substance carried by blood to alter specific target organs
It states signal, source, transport and target effect.
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Make it stick
Describe the complete hormone route without confusing gland, hormone, blood and target.
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.