The body runs the same stimulus–receptor–command centre–effector pathway in two ways. The nervous system sends electrical signals along nerves: fast, short and to one place. The endocrine system sends hormones from glands in the blood: slower, longer-lasting and to target organs anywhere.
Pull your hand off a hot pan and you've done it in a fraction of a second. After lunch, your body brings your blood sugar back down too, but that takes an hour. Same job, different messengers.
Last lesson: every response runs stimulus → receptor → command centre → effector → response. This lesson: the two ways the message is sent.
Engage: Commit to a prediction before you test anything. A wrong guess is fine: it shows you what to look for.
Explore: Try it on the board and compare what happens with your prediction.
Explain: Use the particle model to explain what you saw.
Elaborate: Use the same idea in a new context.
Evaluate: Look back at your first ideas and what changed.
WidthMore contexts, same idea.
Make your prediction first. Help opens once you've locked it in.
EngageCommit to a prediction before you test anything. A wrong guess is fine: it shows you what to look for.
Engage: how does insulin get there?
ExploreTry it on the board and compare what happens with your prediction.
Explore: two pathways
Click a stimulus to send it through the five boxes.
Choose the receptor, command centre and effector for each. Glands are command centres too: they release hormones.
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Send both stimuli through the pathway. What is different about the command centre?
Use the board. This ticks when you get there.
Build all four pathways: two nervous, two hormonal.
Use the board. This ticks when you get there.
ExplainUse the particle model to explain what you saw.
Explain: comparing the two systems
In your book: draw the five-box pathway twice, once for touching a hot pan and once for blood glucose after a meal. Label the messenger between the command centre and the effector in each.
Nervous system or endocrine (hormone) system?
Electrical signals along nerves
Chemical messages carried in the blood
Very fast: a fraction of a second
Slower: seconds to hours
Short-lived: stops when the signal stops
Lasts longer: until the hormone is broken down
Goes to one precise place
Reaches the whole body; only target organs respondEvery cell gets the insulin; only cells with the right receptors respond.
Elaborate TypicalUse the same idea in a new context.
Elaborate: race them
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Run the race.
Use the board. This ticks when you get there.
Elaborate WiderUse the same idea in a new context.
Elaborate: when water is short
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Build all four pathways again, quickly this time.
Use the board. This ticks when you get there.
EvaluateLook back at your first ideas and what changed.
Evaluate: look back
Write one sentence: "At first I thought… Now I think… because…"
Revision summary
Both systems follow stimulus → receptor → command centre → effector → response.
Nervous system: electrical signals along nerves, from the brain or spinal cord. Very fast, short-lived, to one place.
Endocrine system: hormones released by glands (pancreas, adrenal glands, pituitary) into the blood. Slower, longer-lasting, reaching target organs anywhere.
Many responses use both (a fright: a jump from nerves, a pounding heart from adrenaline).
For teachers
Students describe how the nervous and endocrine systems each run the stimulus–receptor–command centre–effector pathway, and compare their signals, speed, duration and reach (AC9S9U01, node 3). About 25 minutes.
I can explain how a nerve signal and a hormone each carry a message.
I can compare how fast each is and how long it lasts.
I can name glands as command centres and target organs as effectors.
Before class
A concept tutorial for introducing or revising the idea. Set the width with ?width=minimum, typical (default) or wider. It sits between Who decides? (the pathway, node 2) and Nerve or hormone? (comparing the systems in context, node 4), which uses the race board in more depth.
Not a hinge node, but students often think every response runs through nerves, or that hormones travel along nerves. The prediction tests the second.
Board notes: the pathways are simplified to five boxes. In the glucose pathway the pancreas both detects the change and releases insulin; in the fright pathway the brain triggers the adrenal glands by a nerve. The race graph is a sketch of the timescales, not measured data.
Running the lesson
Engage: tally the predictions. 'Along a nerve' is the misconception to come back to.
Explore: ask what kind of thing sat in the command centre box for each pathway.
Explain: the sort is the success criterion; the 'why faster' question is the reason.
In your own words: the two five-box pathways with the messenger labelled are the evidence.
The hard part (on purpose)
Placing a gland in the pathway. When a student is stuck on the build board, ask 'what releases the hormone?' and let them find that it is the command centre.
When students get stuck
A student says hormones travel along nerves. Ask: How does a medicine injected in your arm reach your whole body? Fix: In the blood. Hormones are carried the same way.
A student thinks the blood is the command centre. Ask: Does the blood decide anything, or just carry things? Fix: It only carries. The gland that releases the hormone is the command centre.
A student thinks hormones affect every organ. Ask: If insulin reaches your toes, why don't your toes store glucose like the liver? Fix: Only target organs, with the right receptors, respond. The hormone reaches everywhere; the response doesn't.
Stretch and support
Stretch: Type 1 diabetes means the pancreas makes too little insulin. Which part of the pathway fails, and what happens to blood glucose after a meal? (The command centre's message is missing; glucose stays high.)
Support: Give a two-row table: Nervous | Endocrine, with columns Signal, Travels by, Speed, Lasts.
Where it leads
Next: Nerve or hormone? (node 4), then feedback (node 5).
In class: reaction-time ruler drop (nerves) beside a discussion of how long a blush or a fright lasts (hormones); a map of the major glands.
What each step is for
Engage: how does insulin get there?: Students who think all control runs through nerves, or that hormones travel along nerves, pick those options; the blood as the carrier is the idea to build.
Explore: two pathways: Sending a nervous and a hormonal response through the same five boxes, then building four pathways, shows one model with two messengers.
Explain: comparing the two systems: Sorting by signal, speed, duration and reach, then naming glands and target organs, gives students the comparison framework the next lesson uses.
Elaborate: race them: Seeing the two responses to one fright on a time graph turns 'faster' and 'lasts longer' into shapes to read.
Elaborate: when water is short: A second hormone pathway (ADH and the kidneys) checks that students can apply the model to an unfamiliar case.
Now you can
Explain how a nerve signal and a hormone each carry a message.
Compare how fast each is and how long it lasts.
Name glands as command centres and target organs as effectors.