1. Compare the kinds of receptors involved in perceiving sensation with the kinds of energy each sensation is composed of. Consider how the different receptors are suited gٻinteracting with the different kinds of energy.
2. Examine the concept that different receptors can be stimulated to send a message to the wrong area of the brain, which is the final interpreter of the stimulus. Pain is a particularly good topic for discussion, since too much sound, light, pressure, heat, cold, etc., can send the message that there is pain. You might also discuss the fact that a blow to the head may make you "see stars" or a light, even though the visual receptors are not r„æulated.
3. Discuss color blindness as a genetic defect in
the operation of the cones, and ask students to try to determine
how it might arise. Mention the relatedness of the photosynthetic
pigment, bacteriorhodopsin, and ask students to determine why
a similar molecule would be involved in our visual apparatus and
in the chemical that absorbs the energy of light in bacteria.