A.3 Perception of Stimuli

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

DNA codes for each receptor for each smell,

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