1. A.3 Perception of Stimuli

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 the rods and cones to the ganglion cells
Ganglion cells send messages to the brain via the optic nerve
The information form 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
Hairs in the semicircular canals detect movement of the head
Application
Red-green color blindness as a variant of normal trichromatic vision
Detection of chemicals in the air by the many different olfactory receptors
use of cochlear implants by deaf patients
Skill
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

4. DNA codes for each receptor for each smell,

8. Rods and Cones
Rods
Cones
More sensitive to light (function well in dim light)
Less sensitive to light (function well in bright light)
Only 1 type found in retina: it can absorb all wavelengths of visible light
3 types found in retina: 1 – sensitive to red light, 1 – to blue, 1 – green
Impulses from group of rod cells pass to single nerve fiber
Impulse from single cone cell passes to single nerve fiber