A.3 Perception of Stimuli

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

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 wavelengths
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:

Red-green colour-blindness as a variant of normal trichromatic vision
Detection of chemicals in the air by the many different olfactory receptors
Use of cochlear implants in deaf patients

Skills:

Labelling a diagram of the structure of the human eye
Annotation of a diagram of the retina to show the cell types and the direction in which light moves
Labelling a diagram of the structure of the human ear

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.