Body Systems and Negative Feedback: a full term of science

Ten ready-to-teach lessons for Year 9 Biological sciences. Print this pack and the term is prepared: every lesson comes with a step-by-step plan, the questions to ask, a student worksheet, cut-out cards, a class sheet or exit tickets, an assessment kit and worked answers.

Start here: five minutes to Monday

1. Skim the term at a glance on the next page.
2. Print the lesson you need. Each lesson is three A4 sheets: plan, worksheet, and cards, a class sheet or tickets.
3. Gather the few items under “You need” on the plan. Most come from the science prep room or the classroom.
4. Open the free interactive unit on your board or projector. Every plan tells you which picture to show and when.
5. Teach straight from the plan. Timings, talk prompts, misconceptions and worked answers are all on the one page.

For any Year 9 science teacher

The pack suits a biology specialist and a teacher working outside their own subject alike: each plan explains the idea in plain words, lists the misconceptions students bring, and gives worked answers. The big idea of the term: the body senses a change and responds through two coordinating systems. The nervous system sends electrical impulses along neurons, fast and precise; the endocrine system sends hormones in the blood, slower and longer lasting. Many responses are part of negative feedback, in which a change away from a set point is detected and corrected, so body temperature and blood glucose stay within narrow limits.

Two ways to run each lesson

Every lesson works as one 60-minute block, or as two 30-minute sessions; the split point is marked in every plan. Look ahead: Lesson 3 needs a clear plastic screen, Lesson 5 needs a thermometer pair for each group, and Lesson 8 needs a space where students can step up safely.

Safety and care in one look

This term the practical work uses the students’ own bodies, so it stays gentle and voluntary: anyone can be the timer or the recorder instead. In Lesson 3 the paper balls hit a clear screen, never a face. The Lesson 8 step-ups are light, and students with a health condition that limits exercise record rather than step. No blood is tested: the glucose readings are an example. Body data stays private, under first names or numbers.

The term at a glance

One lesson a week for a term. Each lesson stands on the ones before it, so run them in order where you can.

How the sequence builds

Lessons 1 to 3 follow a signal from stimulus to response, measure how long it takes and find the shortcut a reflex uses. Lesson 4 compares the two systems that coordinate a response. Lessons 5 to 7 meet homeostasis: sweating, the negative feedback loops that hold body temperature, and the hormones that hold blood glucose. Lesson 8 measures the body returning to rest after exercise, Lesson 9 sets negative feedback beside positive feedback and single responses, and Lesson 10 brings it together.

Curriculum links (Australian Curriculum V9)

The whole term teaches the Science Understanding descriptor AC9S9U01 quoted on the cover. The lessons also work these Science Inquiry and Human Endeavour descriptors:

Assessment in this pack

• Every plan ends with “Answers and look-fors”: what meeting the idea sounds like in a Year 9 voice, with working.
• The assessment sheet near the front has a class observation checklist and a three-level rubric.
• Lesson 10 is the summative pair: the beach day task, plus the “Show what we know” check.

Materials for the whole term

One gathering session covers all ten lessons, and most of it is already in the science prep room or the classroom. Two things are worth doing ahead: find a clear plastic screen for Lesson 3, and choose a safe place for the Lesson 8 step-ups, such as a low sturdy step or the bottom stair of a staircase with a rail.

The one-trip list

• From the prep room: thermometers, cotton wool, rubber bands, small beakers for water, timers, scissors and glue sticks.
• From the classroom: 30 cm rulers, a chair, scrap paper for paper balls and card to fan with.
• From the office: a clear plastic document sleeve or a sheet of clear plastic.
• For Lesson 8: a sturdy low step, or the bottom stair of a staircase with a rail.

Safety and care in one look

• Every activity on the body is voluntary; anyone can be the timer or the recorder instead.
• The knee jerk is a gentle tap with the side of the hand, never with an object; paper balls are thrown at the clear screen, never at a face.
• Step-ups are light and short; stop at once if anyone feels unwell; students with a condition that limits exercise record.
• No blood is tested, and body data stays private, under first names or numbers.

Assessment without extra work

The term assesses itself. Every lesson plan ends with worked answers and look-fors, and Lesson 10 is the summative pair: the beach day task, in which students explain the body’s responses to six moments of one day, and the final check. This sheet is the place to note what you see along the way.

The three levels

Class observation checklist

A tick a lesson is plenty; the Lesson 10 task and check fill the gaps.

Word wall cards

Cut out the cards and build the wall as the words arrive: stimulus, receptor, effector and response in Lesson 1; reaction time in Lesson 2; neuron, reflex and reflex arc in Lesson 3; nervous system, endocrine system, hormone and gland in Lesson 4; homeostasis and hypothalamus in Lesson 5; set point and negative feedback in Lesson 6; pancreas, insulin, glucagon and diabetes in Lesson 7; positive feedback in Lesson 9.

Dear families

This term in science, Year 9 studies how the body senses a change and responds to it: how a signal travels from the eyes or the skin to the brain and back out to a muscle, how hormones carry slower messages in the blood, and how the body keeps its temperature and its blood glucose steady through negative feedback.

Along the way your student will catch a falling ruler to measure reaction time, test the knee jerk and the blink, watch a wet thermometer cool in a breeze, graph blood glucose after a meal, and time how quickly their heart rate returns to rest after a few minutes of gentle exercise.

Try this at home

• Take turns catching a dropped ruler, in the morning and in the evening. Does the distance change?
• Wet the back of one hand, leave the other dry, and wave both in the air. Which feels colder, and why?
• On a hot day, notice what the body does to cool down; on a cold morning, what it does to warm up.
• Find your pulse at the wrist, count it for 15 seconds and multiply by four. Try it again after climbing some stairs.

What to ask your scientist

• What is the difference between a reflex and a decision?
• How is a hormone different from a nerve signal?
• What does negative feedback mean, and why is it called negative?
• Why do we sweat, and why does a breeze help?

A small note on care: this term’s practical work uses our own bodies, so every activity is gentle and voluntary. If your student has a health condition that limits exercise, please let us know; in the exercise lesson they can be the timer or the recorder.

Warm regards,

The Year 9 science team

Printed from the free seegongsik Body Systems and Negative Feedback teaching pack · seegongsik.com/au/y9/biological/AC9S9U01/pack

From stimulus to response

Every response the body makes follows the same path. A stimulus is a change, outside or inside the body. Receptors detect it; a coordinating system passes the message on, either the nervous system with electrical impulses or the endocrine system with hormones in the blood; and an effector, a muscle or a gland, carries out the response. Students rebuild four pathways from twenty cut-out cards, decide which system coordinates each one, and notice that two of the pathways keep something steady inside the body, an idea the whole term returns to.

We are learning to

• identify the stimulus, receptor, coordination, effector and response in a pathway,
• tell apart the two coordinating systems, the nervous system and the endocrine system,
• explain why a response needs every stage of its pathway.

Success criteria

• I can put the five stages of a response in order and give an example of each.
• I can say which system coordinates a response, and how I know.

You need

• the pathway cards (third sheet), one set per pair, with scissors and glue sticks; a scrunched paper ball for the opening,
• the worksheet (next sheet), one per student.

Lesson flow (about 60 minutes)

Running two half-sessions instead? Do the catch, the board and the card sort in Session A, and Parts B and C in Session B.

Watch for these ideas

• “The brain controls every response.” A reflex is coordinated in the spinal cord, and many responses are carried by hormones in the blood.
• “Receptors and effectors do the same job.” Receptors detect a change; effectors, muscles and glands, act on it.
• “A stimulus comes from outside the body.” A rise in blood glucose after a meal is a stimulus inside the body.

Make it easier, make it bigger

• Easier: give the pair the four pathway names and the five stage names as headings to lay the cards under.
• Bigger: write a fifth pathway of your own for a stimulus inside the body, as five cards, and swap with another pair to rebuild.

Answers and look-fors

• Part A, stimulus to response: a hot pan N, F, Q, C, J; a ball in the air H, T, A, S, L; after a meal R, D, O, K, G; a hot day B, M, I, P, E.
• Part B: a hot pan, nervous system (a reflex through the spinal cord); a ball in the air, nervous system (the brain); after a meal, endocrine system (insulin); a hot day, nervous system (the hypothalamus).
• Part C: 1. The hot pan: the message turns round in the spinal cord. 2. After a meal: insulin, a hormone carried in the blood. 3. Sweat glands, and blood vessels in the skin. 4. After a meal keeps blood glucose steady; a hot day keeps body temperature steady. 5. The ball is seen but not caught: without the effector there is no response, so every stage is needed.
• Look for students who use the words receptor and effector for a part of the body, not for the whole person.

From stimulus to response

A. Rebuild the pathways

Sort the twenty cards into four pathways and put each one in order. Write the card letters.

B. Which system coordinates?

For each pathway, circle the system that passes the message from the receptors to the effectors.

C. Questions

Pathway cards

Cut out the twenty cards. Sort them into four pathways of five, then put each pathway in order from the stimulus to the response.

Teacher note: the answer letters are in the plan. Every pathway has one card for each of the five stages.

How fast can you react?

Every pathway takes time: receptors detect, impulses travel along neurons to the brain and back, and muscles contract. Reaction time is the time from a stimulus to the response. A falling ruler measures it without a stopwatch, because a dropped object falls a known distance in a known time: the further the ruler falls before the catch, the longer the reaction took. Students test a hypothesis about two kinds of stimulus, seeing the ruler drop or feeling a tap on the shoulder as it is let go, and use the mean of many catches because single catches vary a lot.

We are learning to

• write a hypothesis and a reasoned prediction about reaction time,
• measure reaction time with a falling ruler, and convert a distance into a time,
• use repeated trials and a mean to reduce the effect of random error.

Success criteria

• I can turn a ruler distance into a reaction time with the table.
• I can say whether the data supports our hypothesis, using the means, and name one source of error.

You need

• a 30 cm ruler for each pair,
• the worksheet (next sheet), one per student, and the class results sheet (third sheet), one for the board or the wall.

Lesson flow (about 60 minutes)

Running two half-sessions instead? Do the drop, the board and the catches in Session A, and Parts C and D in Session B.

Watch for these ideas

• “Reaction time is how fast your muscles are.” It includes the receptors, the neurons and the brain as well.
• “One catch shows your reaction time.” Single catches vary a lot; the mean of many catches is more reliable.
• “Our touch catches were faster, so touch is always faster.” It held for this class; a general claim needs more people and a fair test.

Make it easier, make it bigger

• Easier: take three catches each way, and read each time straight from the table.
• Bigger: the tap and the drop may not happen at exactly the same moment. Which way would an early tap push the result, and which way a late one? How could the test be made fairer?

Answers and look-fors

• Part A: any testable hypothesis with a reason, for example: the reaction time depends on the kind of stimulus, so a tap will be caught sooner than a sight, because the signal has a shorter path to the brain.
• Conversion table: 5 cm 0.10 s, 10 cm 0.14 s, 15 cm 0.17 s, 20 cm 0.20 s, 25 cm 0.23 s, 30 cm 0.25 s.
• Part C, example class: sight mean 19.3 cm, about 0.20 s, range 15 to 24 cm; touch mean 15.2 cm, about 0.18 s, range 12 to 19 cm.
• Part D: 1. Yes for this class: the touch catches were caught sooner on average. 2. With twelve catches, one slow or quick catch moves the mean only a little. 3. For example: the catcher guesses the moment of the drop, the tap comes early or late, the finger gap changes, or the catcher tires. 4. Changed: the kind of stimulus; measured: the distance fallen; kept the same: the ruler, the starting mark, the finger gap, the hand used and the catcher.
• Bigger: an early tap starts the response before the ruler falls, so the time looks shorter; a late tap lets the ruler fall first, so it looks longer. A sound made by the same hand that lets go, or a ruler released by a clip, would be fairer.

How fast can you react?

A. Our hypothesis

B. Our catches (distance fallen, cm)

From distance to time

For a distance between two columns, the time is between the two times.

C. An example class (distance fallen, cm)

For each row, find the mean distance, the reaction time it gives, and the range.

D. Questions

Class results: sight or touch?

Each pair adds its two means. When the table is full, find the class mean for each stimulus and turn it into a time.

Reaction times are personal data: use first names or numbers, and compare stimuli, not people.

Reflexes: the shortcut

Some responses cannot wait for a decision. A reflex is fast and automatic: the impulse from the receptor travels along a sensory neuron into the spinal cord, crosses to a relay neuron, and leaves straight away along a motor neuron to the effector. The brain is told afterwards, which is why a hand jerks off a hot pan before the pain is felt. Students test two harmless reflexes, the knee jerk and the blink, label a reflex arc, and compare reflex times with the reaction times they measured in Lesson 2.

We are learning to

• describe the path of a reflex arc from the receptor to the effector,
• explain why a reflex is faster than a response that needs a decision,
• use times in seconds to compare responses.

Success criteria

• I can label the five parts of a reflex arc in order.
• I can explain, using times, how a reflex protects the body.

You need

• a chair; a clear plastic screen, such as a document sleeve held flat, and a few scrunched paper balls,
• the worksheet (next sheet), one per student, and the exit tickets (third sheet).

Safety: both tests are voluntary. Tap the knee gently with the side of the hand, never with an object. The paper ball is thrown at the clear screen held in front of the face, never at anyone directly.

Lesson flow (about 60 minutes)

Running two half-sessions instead? Do the hot pan, both reflexes and the board in Session A, and Parts A to C in Session B.

Watch for these ideas

• “The brain controls reflexes.” The reflex arc turns round in the spinal cord; the brain hears about it afterwards.
• “Reflexes are habits we learned.” Reflexes need no learning and no thought, and they happen the same way each time.
• “Pain makes the hand move.” The hand moves first; the feeling of pain comes when the impulses reach the brain.

Make it easier, make it bigger

• Easier: lay the five word wall cards on the desk, label the arc with them, then draw arrows from the receptor to the effector.
• Bigger: the knee jerk arc has no relay neuron: the sensory neuron passes the impulse straight to the motor neuron. Why might that make it faster still?

Answers and look-fors

• Part A: 1 receptor, 2 sensory neuron, 3 relay neuron in the spinal cord, 4 motor neuron, 5 effector (a muscle). The arrows run from the fingertip, into the spinal cord and back out to the arm muscle.
• Part B: the knee-jerk reflex 0.05 s, 4 times as fast as the catch; blinking at a puff of air 0.1 s, 2 times as fast as the catch; the catch itself, 0.2 s.
• Part C: 1. The impulse turns round in the spinal cord, so it does not wait for the brain to decide. 2. The sooner the hand leaves the pan, or the eye closes, the smaller the injury. 3. The catch needs the brain to see the ruler and decide to close the fingers; the reflex needs no decision. 4. The feeling of pain needs impulses to reach the brain, which comes after the reflex has acted.
• Bigger: one fewer neuron means one fewer gap to cross, and each crossing takes a little time.
• Exit tickets: 1. Receptor, sensory neuron, relay neuron, motor neuron, effector. 2. In the spinal cord. 3. Faster: it needs no decision by the brain.

Reflexes: the shortcut

A. Label the reflex arc

A finger touches a hot plate. Write the part at each number, then draw arrows to show the way the impulse travels.

B. A reflex or a decision?

C. Questions

Exit tickets

Cut out one ticket for each student.

Nervous or endocrine?

The body has two coordinating systems. The nervous system sends electrical impulses along neurons: fast, aimed at one muscle or gland, and over as soon as the impulses stop. The endocrine system releases hormones from glands into the blood: slower, reaching every organ the blood reaches, and lasting minutes, hours or years, as long as the hormone stays in the blood. Only target cells with the right receptors respond to a hormone. Many responses use both systems, and the hypothalamus in the brain links them. Students sort twelve statements, then locate five glands and the hormones they release.

We are learning to

• compare how the nervous and endocrine systems carry signals, how fast and for how long,
• name five endocrine glands and a hormone from each,
• explain why some responses use both systems.

Success criteria

• I can sort statements about the two systems and justify each choice.
• I can locate the pituitary, the thyroid, the adrenal glands, the pancreas and the ovaries or testes, with a hormone from each.

You need

• the system cards (third sheet), one set per pair, with scissors,
• the worksheet (next sheet), one per student.

Lesson flow (about 60 minutes)

Running two half-sessions instead? Do the messages, the board and the card sort in Session A, and Parts B and C in Session B.

Watch for these ideas

• “Hormones travel along nerves.” Hormones travel in the blood; only nerve impulses travel along neurons.
• “A hormone acts on every cell it reaches.” Only target cells with the matching receptors respond.
• “The endocrine system is only about growth and puberty.” It also holds blood glucose, water balance and much else steady.

Make it easier, make it bigger

• Easier: sort first the cards about how the signal travels and how fast, then the rest.
• Bigger: in a fright, nerves signal the adrenal glands to release adrenaline. Explain why a fright uses both systems, and why the heart keeps pounding for a while after the danger has passed.

Answers and look-fors

• Part A: nervous system A, D, F, K, L; endocrine system C, E, H, J; both B, G, I.
• Part B: 1 pituitary gland, growth hormone, controls growth, and controls several other glands; 2 thyroid gland, thyroxine, sets how fast cells use energy; 3 adrenal glands, adrenaline, readies the body for action: a faster heart and more glucose in the blood; 4 pancreas, insulin and glucagon, keep blood glucose within its limits; 5 ovaries or testes, oestrogen or testosterone, bring about the changes of puberty.
• Part C: 1. The nervous system: it is fast and aimed at the arm muscles. 2. The hormone stays in the blood and keeps reaching its target cells until it is broken down. 3. Only target cells with receptors for that hormone respond.
• Bigger: the fright is sensed and passed on by nerves, which signal the adrenal glands; adrenaline in the blood then reaches the heart and many organs, and keeps acting until it is broken down.

Nervous or endocrine?

A. Our sort

Write the letters of the cards in each pile.

B. Glands and hormones

Write the gland at each number, a hormone it releases and what that hormone does. Use the word bank for the glands.

C. Questions

Nervous system, endocrine system, or both?

Cut out the cards. Lay down the three grey heading cards, then sort the statements under them.

Teacher note: the piles are not the same size. The answer letters are in the plan.

Keeping cool

The body works best near 37 °C, and keeping it there while the weather, the sun and our own muscles add heat is part of homeostasis: keeping conditions inside the body steady. The hypothalamus in the brain watches the temperature of the blood. When it rises, sweat glands release sweat onto the skin, and as the sweat evaporates it takes heat from the skin with it. Students measure that cooling with two thermometers, one dry and one with its bulb in wet cotton wool, first in still air and then in a breeze.

We are learning to

• explain how the evaporation of sweat cools the skin,
• measure and graph a temperature change over time, with a control,
• link sweating to keeping body temperature steady.

Success criteria

• I can graph the three thermometers and describe how they differ.
• I can explain why a breeze cools a wet surface faster than still air.

You need

• for each group: two thermometers, cotton wool, a rubber band, a little water at room temperature, a sheet of card to fan with and a timer,
• the worksheet (next sheet), one per student, and the exit tickets (third sheet).

Safety: thermometers are fragile, so lay them flat on the bench and never shake them; wipe up spills.

Lesson flow (about 60 minutes)

Running two half-sessions instead? Do the pool, the board and both runs in Session A, and Parts B and C in Session B.

Watch for these ideas

• “Sweat cools you because it is cold.” Sweat leaves the body at body temperature; it cools the skin as it evaporates.
• “Sweating is the only way to lose heat.” Blood vessels in the skin also widen, so more warm blood flows near the surface and loses heat.
• “We only sweat when we exercise.” We sweat whenever body temperature starts to rise, including on a hot day at rest.

Make it easier, make it bigger

• Easier: read the thermometers only at the start and at 6 minutes, and graph the example readings.
• Bigger: on a humid day, sweat evaporates slowly. Predict how the wet bulb would behave on a humid day, and explain why humid heat is harder on the body than dry heat.

Answers and look-fors

• Part A, example class: the dry bulb changed by 0.0 °C; the wet bulb fell 3.3 °C in still air and 5.2 °C in a breeze.
• Part B: the dry line stays flat; both wet lines fall fastest in the first minutes and then level off, and the breeze line falls further.
• Part C: 1. It is the control: it shows that the room itself did not cool. 2. Water evaporating from the cotton wool takes heat from the bulb. 3. The breeze carries the damp air away, so more water can evaporate each minute. 4. Sweat evaporating from the skin cools the skin and the blood flowing just under it, and the cooler blood carries the body temperature back towards 37 °C.
• Bigger: the wet bulb would cool less, because humid air already holds a lot of water, so sweat evaporates slowly and cools the body less.
• Exit tickets: 1. As sweat evaporates it takes heat from the skin. 2. About 37 °C. 3. A breeze, or dry air.

Keeping cool

A. Temperature (°C)

B. Graph

Plot all three thermometers on the same axes, join each set of points, and add a key.

C. Questions

Exit tickets

Cut out one ticket for each student.

Negative feedback loops

When body temperature rises, the body responds to bring it down; when it falls, the body responds to bring it up. Because the response always works against the change, this is called negative feedback. Every loop has the same parts: a change away from the set point, receptors that detect it, a control centre that compares it with the set point (for temperature, the hypothalamus), effectors that respond, and a response that brings the value back. As the value returns, the receptors detect that too, and the response eases off. Students rebuild the two temperature loops from cards and name every part.

We are learning to

• describe the steps of a negative feedback loop in order,
• identify the receptors, the control centre and the effectors for body temperature,
• explain why the response must ease off as the value returns to the set point.

Success criteria

• I can rebuild both temperature loops in order and label each part.
• I can explain what makes the feedback negative.

You need

• the loop cards (third sheet), one set per pair, with scissors and glue sticks,
• the worksheet (next sheet), one per student.

Lesson flow (about 60 minutes)

Running two half-sessions instead? Do the thermostat, the board and the cards in Session A, and Parts B and C in Session B.

Watch for these ideas

• “Negative feedback is bad for you.” Negative means the response works against the change; it keeps the body stable.
• “Body temperature is exactly 37 °C all the time.” It moves a little around the set point through the day.
• “The skin is the control centre.” The skin has receptors; the hypothalamus in the brain compares and coordinates.

Make it easier, make it bigger

• Easier: give each pair the first card of each loop, the change, to start from.
• Bigger: in a fever, the hypothalamus raises the set point for a while. Explain why a person can feel cold and shiver while their temperature is rising.

Answers and look-fors

• Part A: too hot F, K, A, I, G, D; too cold C, J, E, L, B, H.
• Part B, too hot: the change, temperature rises; receptors in the skin and the brain; the control centre, the hypothalamus; effectors, sweat glands and widening blood vessels in the skin; the response, heat is lost and the temperature falls. Too cold: the temperature falls; the same receptors and control centre; effectors, muscles that shiver and narrowing blood vessels in the skin; the response, heat is made and kept in, and the temperature rises.
• Part C: 1. The response is the opposite of the change: a rise brings on cooling, a fall brings on warming. 2. The temperature would keep falling past 37 °C, and the body would become too cold. 3. The receptors and the control centre are the same; the effectors differ.
• Bigger: with the new, higher set point, a normal temperature is compared with it and reads as too cold, so the body shivers and narrows the blood vessels in the skin until the temperature reaches the new set point.

Negative feedback loops

A. The cards in order

Write the letters of each loop in order, starting from the change.

B. Two loops, one control centre

Write in each box what happens at that part of the loop, in your own words.

C. Questions

Loop cards

Cut out the twelve cards. Sort them into two loops of six, too hot and too cold, then put each loop in order, starting from the change.

Teacher note: the answer letters are in the plan. Glued in a ring, the last card of each loop leads back to the first.

Blood glucose

Cells take glucose from the blood for energy, so its level is held within limits: in a healthy person, roughly 4 to 8 mmol/L (millimoles per litre), lower before meals and higher for an hour or so after. After a meal, glucose from digested food enters the blood. Cells in the pancreas detect the rise and release insulin, a hormone that makes liver and muscle cells take glucose in and store it as glycogen, so the level falls. Between meals, as the level drops, the pancreas releases glucagon, which makes the liver turn glycogen back into glucose. Two hormones, working in opposite directions, make one negative feedback system. Students graph one person’s readings after breakfast and trace both loops.

We are learning to

• describe how insulin and glucagon keep blood glucose within limits,
• graph and interpret readings taken over time,
• explain diabetes as a feedback system that does not work as it should.

Success criteria

• I can graph the readings and say when insulin was acting.
• I can explain blood glucose control as negative feedback, with the pancreas as the control centre.

You need

• the worksheet (next sheet), one per student, and the exit tickets (third sheet),
• nothing else: the readings are an example, and no blood is tested in class.

Care: some students live with diabetes. Keep the talk on how the system works, never on any one person, and leave questions about a person’s own care to their doctor.

Lesson flow (about 60 minutes)

Running two half-sessions instead? Do breakfast, the board and the graph in Session A, and Parts C and D in Session B.

Watch for these ideas

• “Insulin is a kind of sugar.” Insulin is a hormone: a signal that tells cells to take glucose in.
• “Glucagon and glycogen are the same thing.” Glucagon is the hormone; glycogen is the glucose stored in the liver and the muscles.
• “Blood glucose should stay perfectly flat.” It rises after a meal and falls back; control keeps it within limits, not at one number.

Make it easier, make it bigger

• Easier: plot the points together on the board first; students join them and mark the peak.
• Bigger: continuous glucose monitors are small sensors worn on the skin that read glucose every few minutes, day and night. What can scientists now see about glucose control that a few finger-prick readings a day could not show?

Answers and look-fors

• Part A: the line rises from 5.0 to a peak of 7.4 mmol/L at 30 minutes, then falls to 4.9 mmol/L by 120 minutes.
• Part B: 1. 2.4 mmol/L. 2. Insulin, from the peak at 30 minutes onwards. 3. Just below where it started; if it kept falling, the pancreas would release glucagon, and the liver would release stored glucose.
• Part C, too high: glucose rises after a meal; detected by cells in the pancreas; insulin; liver and muscle cells; glucose is taken out of the blood and stored, so the level falls. Too low: glucose falls between meals; the pancreas; glucagon; liver cells; stored glucose is released, so the level rises.
• Part D: 1. Little or no insulin is released, so glucose is not taken out of the blood after a meal and stays high. 2. The control centre still works but the effectors respond less, so glucose stays high for longer.
• Exit tickets: 1. The pancreas. 2. Insulin lowers blood glucose; glucagon raises it. 3. Negative feedback: each hormone works against the change.

Blood glucose

A. One person’s morning

A healthy person ate breakfast at 0 minutes. Plot the readings and join the points.

B. Read the graph

C. Two hormones, one system

D. When the system does not work

Exit tickets

Cut out one ticket for each student.

Back to rest

Exercise disturbs the body: working muscles use more oxygen and make more carbon dioxide and more heat. Receptors detect the changes, and the nervous system and the hormone adrenaline speed up the heart and the breathing, so more blood carries oxygen in and carbon dioxide out. When the exercise stops, negative feedback brings both rates back towards their resting values. Students count their own heart rate and breathing rate before and after two minutes of gentle step-ups, graph the recovery, and read off how long each rate takes to return near rest.

We are learning to

• measure heart rate and breathing rate with care, and repeat the measurement at set times,
• graph a recovery and read values from it,
• explain recovery after exercise as negative feedback, and consider the ethics of collecting data about people.

Success criteria

• I can graph both rates through recovery and say when each came back near rest.
• I can explain why both rates rise during exercise and fall afterwards.

You need

• for each group of three: a sturdy low step or the bottom stair, and a timer or a clock with a second hand,
• the worksheet (next sheet), one per student, and the exit tickets (third sheet).

Safety and ethics: the step-ups are gentle, at a steady walking pace. Anyone may be the timer or a counter instead, and students with a health condition that limits exercise always count. Stop at once if anyone feels dizzy or unwell. Body data is personal: record first names or numbers, and compare the rates, not the people.

Lesson flow (about 60 minutes)

Running two half-sessions instead? Do the bus, the counting practice and the step-ups in Session A, and Parts B and C in Session B.

Watch for these ideas

• “The heart speeds up because you decide it should.” It is automatic: receptors detect the changes, and nerves and adrenaline speed up the heart.
• “Breathing faster is only about getting oxygen in.” It also removes the extra carbon dioxide the muscles make.
• “The fastest recovery wins.” Recovery varies with many things; this is about how the system works, not a contest between people.

Make it easier, make it bigger

• Easier: count heart rate only, and graph the example breathing rates.
• Bigger: plan a valid test of whether a longer time of exercise gives a longer recovery. What would you change, measure and keep the same, and what would you do to keep it safe and fair to the people taking part?

Answers and look-fors

• Part A, example: heart rate 72 at rest, 128 at the end of the exercise; breathing rate 14 at rest, 32 at the end.
• Part B: both lines jump at the end of the exercise and then fall, quickly at first and then more slowly, levelling off near the resting value.
• Part C: 1. Heart rate rose by 56 beats per minute and breathing rate by 18 breaths per minute. 2. Breathing came back within 2 breaths of rest after 3 minutes; heart rate came back within 5 beats of rest after 5 minutes. 3. Working muscles need more oxygen and make more carbon dioxide; faster breathing and a faster heart carry oxygen in and carbon dioxide out. 4. Receptors detect the extra carbon dioxide; the response removes it; as it returns to normal the receptors detect that too, and the rates slow: the response works against the change.
• Bigger: change the time of exercise; measure the time for heart rate to return near rest; keep the same step, pace, stepper and counting method; anyone can opt out, and nobody exercises hard.
• Exit tickets: 1. For example, more carbon dioxide in the blood, or a rise in body temperature. 2. It falls back towards the resting rate. 3. Negative feedback.

Back to rest

A. The rates (per minute)

End = straight after two minutes of step-ups. 1 to 5 = minutes of recovery, sitting down.

B. Graph

Plot both rates on the same axes, join each set of points, and add a key.

C. Questions

Exit tickets

Cut out one ticket for each student.

Negative, positive or a single response?

Not every response is negative feedback. A single response, such as a reflex or catching a ball, answers one stimulus and is over. Negative feedback keeps a value near its set point by working against every change, so the value stays stable. Positive feedback does the opposite: the response makes the change bigger, which brings on more response, so it runs on until something else stops it, as when a clot seals a cut. The body relies on negative feedback for stability and uses positive feedback only for changes that must be finished quickly. Students sort twelve examples and explain why the body cannot do without negative feedback.

We are learning to

• tell apart negative feedback, positive feedback and a single response,
• explain why negative feedback keeps conditions stable,
• give an example of positive feedback, in the body and outside it.

Success criteria

• I can sort the twelve examples and give a reason for each.
• I can explain what would happen to body temperature without negative feedback.

You need

• the feedback cards (third sheet), one set per pair, with scissors,
• the worksheet (next sheet), one per student.

Lesson flow (about 60 minutes)

Running two half-sessions instead? Do the squeal, the board and the sort in Session A, and Parts B and C in Session B.

Watch for these ideas

• “Positive feedback is good and negative feedback is bad.” The names describe the direction of the response, not whether it helps.
• “Every response is feedback.” A reflex answers one stimulus; nothing is held at a set point.
• “Positive feedback never stops.” It runs until something ends it, such as the clot sealing the cut.

Make it easier, make it bigger

• Easier: sort into two piles first, feedback and a single response, then split the feedback pile in two.
• Bigger: find another example of positive feedback outside the body, and say what stops it.

Answers and look-fors

• Part A: negative feedback A, D, F, G, L; positive feedback C, H, J; a single response B, E, I, K.
• Part B, the reason for each card: A the response lowers the temperature back towards 37 °C; B a reflex to one stimulus; nothing is held at a set point; C the change grows until the clot is made; D the response raises the temperature back towards 37 °C; E a decision and an action, then it is over; F the response lowers the glucose back towards the set point; G the response raises the glucose back towards the set point; H each loop round makes the sound bigger; I a startle to one stimulus; J the change feeds itself; K a reflex, over in a moment; L the response lowers the carbon dioxide back towards normal.
• Part C: 1. It would keep rising or falling: in the heat the body would overheat, and in the cold it would keep cooling. 2. The cut is sealed: the clot is finished, so the change stops. 3. Negative feedback holds conditions steady, which cells need; positive feedback would push them further away. 4. The fruit ripens, gives off more gas and ripens more, until the fruit is ripe.
• Bigger: for example, snow melting on a sunny slope uncovers darker ground, which warms faster and melts more snow, until the snow is gone.

Negative, positive or a single response?

A. Our sort

Write the letters of the cards in each pile.

B. Three cards, three reasons

Choose one card from each pile and explain why it belongs there.

C. Questions

Negative feedback, positive feedback, or a single response?

Cut out the cards. Lay down the three grey heading cards, then sort the examples under them.

Teacher note: the piles are not the same size. The answer letters and the reasons are in the plan.

Show what we know

The term comes together. In the task, students follow Jordan through a day at the beach: two body temperatures, two blood glucose readings, a reflex and a decision. For each moment they decide whether it is negative feedback or a single response, name the system that coordinates it, and describe the effectors and the response. Then they sit the eight-question final check, and the class plays the unit quiz as a game on the board.

We are learning to

• apply the stages of a response and the idea of negative feedback to new situations,
• choose the coordinating system for a response and justify the choice,
• use readings to describe a change away from a set point and back.

Success criteria

• I can explain each moment of the beach day with the right kind of response, system and effectors.
• I can answer the final check on my own.

You need

• the task (next sheet) and the final check (third sheet), one each per student,
• the interactive unit open on the board for the quiz; mini whiteboards if you have them.

Lesson flow (about 60 minutes)

Running two half-sessions instead? Do the stages and the beach day in Session A, and the final check and the quiz in Session B.

Watch for these ideas

• Students who call every response feedback: ask which set point is being held.
• Students who name the brain as the control centre for blood glucose: the pancreas both detects the change and releases the hormones.
• Students who say the swim made the body temperature fall because the water is cold, and stop there: ask what the body did next.

Make it easier, make it bigger

• Easier: give the kinds of response and the systems as a list to choose from for the task.
• Bigger: add a seventh moment of your own to the beach day, with a reading, and explain it the same way.

Answers and look-fors

• Task: Noon, negative feedback, nervous system (the hypothalamus): sweat glands release sweat and blood vessels in the skin widen; heat is lost and the temperature falls; 12:30 pm, a single response (a reflex), nervous system (the spinal cord): the leg muscles lift the foot off the sand; 1 pm, negative feedback, endocrine system (insulin from the pancreas): liver and muscle cells take glucose in and store it; the level falls; 3 pm, negative feedback, nervous system (the hypothalamus): muscles shiver and blood vessels in the skin narrow; heat is made and kept in, and the temperature rises; 3:30 pm, a single response (a decision), nervous system (the brain): the arm and hand muscles move to catch the frisbee; 5 pm, negative feedback, endocrine system (glucagon from the pancreas): liver cells release stored glucose into the blood; the level rises.
• Task questions: 1. 0.6 °C above the morning reading of 36.8 °C, and 0.3 °C below it after the swim. 2. It fell 2.9 mmol/L; insulin lowered it, and glucagon will stop it falling further. 3. Both are kept near a set point by negative feedback: each change brings on a response that works against it.
• Final check: 1. Stimulus, receptor, coordination, effector, response. 2. A hormone. 3. The catcher whose ruler fell 10 cm: the ruler had less time to fall. 4. The impulse turns round in the spinal cord, without waiting for a decision by the brain. 5. The hypothalamus. 6. Insulin. 7. Negative feedback. 8. A rise in temperature brings on sweating, which cools the body back towards the set point: the response works against the change.
• Mark the task against the rubric in the assessment kit; the check covers stimulus and response, the two systems and feedback.

A day at the beach

In the morning, Jordan’s body temperature is 36.8 °C. For each moment of the day, decide whether it is negative feedback or a single response, name the system that coordinates it, and describe the effectors and what they do.

Show what we know