• 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.

1. How do hormones travel around the body? (through the air / along nerves as electrical impulses / in the blood / through the bones) → in the bloodPrompt: Hormones are chemical messengers.
2. Coordination and control: which statement is true? (Reflex actions are controlled by conscious thought. / Adrenaline (epinephrine) prepares the body for "fight or flight". / Hormones travel along nerves. / Insulin raises blood glucose.) → Adrenaline (epinephrine) prepares the body for "fight or flight".Prompt: Nerves carry electrical impulses; hormones are chemicals.
3. 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.

• 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.

• 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.

• Do these together. Students try each step on whiteboards before you reveal it.
• Use the hints as prompts rather than giving the answer.

1. In a ruler-drop test, a student's reaction times were 0.26 s, 0.24 s, 0.25 s. What is the mean reaction time, in s? Give 2 decimal places. → 0.25 sPrompt: Add the three times.
2. A student's reaction time is longer after staying up late. This shows reaction time can be affected by… (eye colour / tiredness / shoe size / blood group) → tirednessPrompt: What changed for the student?

• 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.

• Two questions on their own. Sort answers into got it / nearly / not yet to plan the next lesson.

1. How does a signal cross a synapse (the gap between neurones)? (An electric spark jumps across / Chemicals diffuse across the gap / The neurones touch and fuse / Blood carries it) → Chemicals diffuse across the gapPrompt: These chemicals are called neurotransmitters.
2. In a ruler-drop test, a student's reaction times were 0.23 s, 0.24 s, 0.23 s. What is the mean reaction time, in s? Give 2 decimal places. → 0.23 sPrompt: Add the three times.

Free online practice with hints and printable worksheets for this skill: eurekami.com/science/grade-10.