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.