Action potential of single nerve fibres in the earthworm

The aim of this experiment is to demonstrate some fundamental physiological properties of the nerve impulse. In this experiment, students stimulate, and record extracellularly from giant axons of the earthworm.

It is suitable for beginning undergraduates in Zoology, Physiology, Psychology, and related subjects. Basic familiarity with the PowerLab data acquisition system and Scope software is assumed.

Click the links below to download LabChart 5 Windows and Mac versions of the Teaching Experiment. If you are using LabChart 4, please download the Teaching Experiment from the LabChart 4 Teaching Experiments page.

Earthworm_AP_Win.zip (6.4 MB) Earthworm_AP_Mac.sit (5.5 MB)

Click the links below to download a short Technique Movie in your preferred compressed format. The movie shows how to set up and perform this experiment.

Earthworm.zip (2 MB) Earthworm.sit (1.9 MB)

The documentation for this experiment assumes the use of:

PowerLab 4/25T  (ML865)
Stimulator cable, consisting of BNC connectors to alligator-clips
Shielded BioAmp Cable
Shielded 5 Snap-connect lead wires (modified)
   or Two custom shielded recording leads and a ground lead (see Demonstrator Notes)
3 silver wires, chlorided
Blu-tack™ or similar plasticine
Corkboard
4 metal pins
Small dish (Petri dish or similar)
10% ethanol in 0.25% NaCl solution
One millilitre plastic syringe
Ruler with millimetre divisions
Paper tissues
Earthworms (at least 60 mm in length)

For equipment substitutions see Equipment.