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Full access The human bodyArt and pattern

The reflex arc: a signal follows its path

Draw a flat PLA reflex arc over printed plan T1: a spinal cord ring with a reflex centre, five stations (receptor, sensory neuron, centre, motor neuron and effector) joined by pathways, and a signal marker. Guide the marker through the stations, block the pathway with a strip at two sites and predict the effects. The extension adds a branch to the brain with a removable insert.

Age
12–14 years
Length
approx. 45 min
Level
Easy
Where you teach
School
Purpose
Educational
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How to run this session

Stages and timing
  1. Spinal cord ring
  2. Reflex centre and marker
  3. Sensory pathway stations
  4. Sensory pathway: towards the spinal cord
  5. The signal’s first journey
  6. Motor pathway stations
  7. Motor pathway: towards the muscle
  8. The complete arc and an interrupted pathway
  9. Extension: brain and insert
  10. Extension: compare the pathways

What gets built

A flat, hands-on knee-reflex diagram with five stations and a marker, plus an observation sheet recording the link sequence and predictions for two interruptions.

What it practises
  • Ordering the links of a reflex arc
  • Predicting the effects of pathway interruption
  • Distinguishing reflexes from conscious decisions

Success criteria
  • I identify the five reflex-arc stations in the correct order and name each one.
  • I guide the marker from receptor to effector and explain where the signal enters the spinal cord (dorsal side) and leaves it (ventral side).
  • I predict the effects of interrupting the sensory pathway (X1) and motor pathway (X2) before checking with the marker.
  • I distinguish the knee reflex (automatic, with its centre in the spinal cord) from a movement based on a decision (involving the brain).
  • I explain a model limitation, such as the interneuron in a withdrawal reflex or the thousands of neurons in a nerve.

What you need
Filament
PLA
Colours
colour shown in the illustration, colour shown in the illustration
Also
3D pen for PLA: 1 per pupil, Transparent work mat: 1 per pupil, T1: 1:1 reflex-arc plan: 1 per pupil, T2: observation sheet: 1 per pupil, BREAK-strip cutout sheet (2 copies): 1 per pupil, Pencil: 1, Ruler: 1, Scissors: 1 per pair

Files

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Version 93922f54-42bd-4cc8-b175-70db098d5de6 Updated 2026-10-13

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