Science lesson plan · 10th grade (Year 11 in England) · 45 minutes
Reflex arcs and reaction times
Human body and health
CCSS NGSS.HS-LS1-2CCSS NGSS.SEP 3England: GCSE Combined Science: Homeostasis and responseEngland: GCSE Combined Science: required practical (reaction time)
Objective and success criteria
Students will: Reflex arcs and reaction times.
- I can answer questions on today's skill on my own, without help.
- I can explain each step and say why it works.
- I can check my answer and spot a mistake.
Before and after
Needs first: Nervous system, reflexes and hormones
Leads to: the next skill in this area.
Materials: Stopwatches, Body diagrams, Mini whiteboards, A diagram or short video clip of the idea, Printed student sheet (below).
Warm-up · 5 min
- Quick retrieval from earlier learning (Nervous system, reflexes and hormones). Students answer on mini whiteboards.
- Show answers together and note who needs support in the main task.
- Why are reflexes useful? (They are slow and careful / They let us think carefully first / They only happen when we sleep / They are fast and automatic, protecting the body from harm) → They are fast and automatic, protecting the body from harmPrompt: The message does not have to go to the conscious brain.
- Coordination and control: which statement is true? (Insulin raises blood glucose. / Reflex actions are controlled by conscious thought. / Hormones travel along nerves. / Normal human body temperature is about 37 °C.) → Normal human body temperature is about 37 °C.Prompt: Nerves carry electrical impulses; hormones are chemicals.
- How do hormones travel around the body? (along nerves as electrical impulses / through the bones / through the air / in the blood) → in the bloodPrompt: Hormones are chemical messengers.
Hook · 5 min
- Ask everyone to find their pulse, then jump for 30 seconds and find it again.
- Share the objective: Reflex arcs and reaction times. Read the success criteria together.
I do: model it · 10 min
- Work through the example out loud, saying why you do each step, not just what you do.
- Example: In a ruler-drop test, a student's reaction times were 0.19 s, 0.2 s, 0.23 s. What is the mean reaction time, in s? Give 2 decimal places.
- Step 1: (0.19 + 0.2 + 0.23) ÷ 3 = 0.207
- Step 2: So the answer is: 0.21 s
- Answer: 0.21 s
- Pause after each step and ask a student to say what comes next.
We do: guided practice · 10 min
- Do these together. Students try each step on whiteboards before you reveal it.
- Use the hints as prompts rather than giving the answer.
- In a ruler-drop test, a student's reaction times were 0.21 s, 0.24 s, 0.24 s. What is the mean reaction time, in s? Give 2 decimal places. → 0.23 sPrompt: Add the three times.
- How does a signal cross a synapse (the gap between neurones)? (An electric spark jumps across / The neurones touch and fuse / Chemicals diffuse across the gap / Blood carries it) → Chemicals diffuse across the gapPrompt: These chemicals are called neurotransmitters.
You do: independent practice · 10 min
- Students work on the student sheet. Circulate and check the first two answers of every student early.
- Students who finish: write a question of their own for a partner, with the answer.
The 8 questions are on the student sheet below, with answers in the key.
Exit ticket · 5 min
- Two questions on their own. Sort answers into got it / nearly / not yet to plan the next lesson.
- A student's reaction time is longer after staying up late. This shows reaction time can be affected by… (eye colour / blood group / shoe size / tiredness) → tirednessPrompt: What changed for the student?
- In a ruler-drop test, a student's reaction times were 0.21 s, 0.2 s, 0.23 s. What is the mean reaction time, in s? Give 2 decimal places. → 0.21 sPrompt: Add the three times.
Watch out for
- Everyday meanings of words getting in the way of the science meaning: define key words explicitly.
- Remembering facts without the reason: ask "why?" and "what is the evidence?"
Support and stretch
Support
- Review first: Nervous system, reflexes and hormones.
- Use concrete materials: stopwatches.
- Give the first step of each question, or a partly worked example to finish.
- Pair with a confident partner for the guided practice.
Stretch
- Explain a common mistake in writing and how to fix it.
- Write a word problem that uses today's skill, then solve a partner's.
Homework and more practice
Free online practice with hints and printable worksheets for this skill: eurekami.com/science/grade-10.
Free lesson plan from eurekami.com/lesson-plan-builder