A.3: Perception of stimuli

Essential idea: Living organisms are able to detect changes in the environment.

Nature of science: 

Understanding of the underlying science is the basis for technological developments—the discovery that electrical stimulation in the auditory system can create a perception of sound resulted in the development of electrical hearing aids and ultimately cochlear implants. (1.2)

Understandings:

• Receptors detect changes in the environment.

• Rods and cones are photoreceptors located in the retina.

• Rods and cones differ in their sensitivities to light intensities and wavelengths.

• Bipolar cells send the impulses from rods and cones to ganglion cells.

• Ganglion cells send messages to the brain via the optic nerve.

• The information from the right field of vision from both eyes is sent to the left part of the visual cortex and vice versa.

• Structures in the middle ear transmit and amplify sound.

• Sensory hairs of the cochlea detect sounds of specific frequency.

• Impulses caused by sound perception are transmitted to the brain via the auditory nerve.

• Hair cells in the semicircular canals detect movement of the head.

Applications and skills:

• Application: Red-green colour-blindness as a variant of normal trichromatic vision.

• Application: Detection of chemicals in the air by the many different olfactory receptors.

• Application: Use of cochlear implants in deaf patients.

• Skill: Labelling a diagram of the structure of the human eye.

• Skill: Annotation of a diagram of the retina to show the cell types and the direction in which light moves.

• Skill: Labelling a diagram of the structure of the human ear.

Guidance:

• Humans’ sensory receptors should include mechanoreceptors, chemoreceptors, thermoreceptors and photoreceptors.

• Diagram of human eye should include the sclera, cornea, conjunctiva, eyelid, choroid, aqueous humour, pupil, lens, iris, vitreous humour, retina, fovea, optic nerve and blind spot.

• Diagram of retina should include rod and cone cells, bipolar neurons and ganglion cells.

• Diagram of ear should include pinna, eardrum, bones of the middle ear, oval window, round window, semicircular canals, auditory nerve and cochlea.