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PSYCH 2220 Sensation and Perception (I) Lecture 2 Keywords for lecture 1 electromagnetic spectrum, (pit viper), mechanical energy, chemical energy, stages of vision, (i) eye movements, (ii) focus, (iii) light regulation, pupil, pin-hole camera, refraction, focus, cornea, lens, accommodation, myopia, hyperopia, astigmatism, presbyopia Eye movements Point eyes to right place Accommodation focus Pupils Light Adaptation Adjust for the light level Transduction Convert light energy to activity in cells SHORT SIGHTED (Myopia) DISTANT OBJECT eg. star Even the relaxed lens is too strong. The rays are focused in front of the retina! DISTANT OBJECT eg. star The CONCAVE lens makes the rays DIVERGE, thus compensating for the unwanted strength of the eye's optics. The eye and its optics 4 - 5 LONG SIGHTED (Hyperopia) CLOSE OBJECT The fully-contracted lens cannot get strong enough. The rays are focused behind the retina! CLOSE OBJECT The CONVEX lens helps the rays CONVERGE, thus assisting the inadequate strength of the eye's optics. The eye and its optics 4 - 6 With age, the lens becomes less flexible and accommodation becomes fixed at some distance. This fixing of the focal length of the lens is called PRESBYOPIA. The refracting power of the eye may not be the same in all dimensions. This is called ASTIGMATISM. Side view Flatter Top view For this person, the cornea is flatter from left to right than it is from top-to-bottom. Therefore, for this astigmatic person, vertical lines would be better in focus than horizontals. Photo taken through a LARGE aperture shallow depth of field (only one distance is in focus) Photo taken through a SMALL aperture long depth of field (lots of distances are in focus) Most of the refraction takes place at the air/water boundary of the CORNEA in the air Lens in the eye of an AIR-LIVING animal AIR LIVING No refraction takes place at the water/water boundary of the CORNEA in the water Lens in the eye of a WATER-LIVING animal WATER LIVING DIVING ANIMALS 1 put on a mask that keeps air in front of cornea 2 rely on a STRONG lens that can change from air-living to water living eg: otter Air Type 3 Have a FLAT cornea (to remove its influence) and then use a WATER-LIVING style lens eg. Penguin, flying fish Water Type 4 Have two pairs of eyes - one for each environment eg. Four-eyed fish 5 Use a WATER-LIVING style lens in the water and bi-pass the cornea by using a PIN HOLE pupil on land eg. seal 1. Diving mask 2. strong The Otter - who can change her eye from ..... … Air Type … to…. ….Water Type 3. Flat cornea + fish-type lens 4. Four eyes (!) Four-eyed fish 4. Four eyes (!) 5. Pin hole on land; fish-type in water Human using the seal solution Antony van Leeuwenhoek (1632-1723) Leeuwenhoek’s Microscope Na+ nucleus K+ cytoplasm membrane Potassium K+ (Latin Kalium) Sodium Na+ (Latin Natrium) extra-cellular fluid NERVE CELL ONE WAY synapse voltage dependent sodium channels neurotransmitters ACTION POTENTIAL THE CELL CONCEPT KEYWORDS: Cell, membrane, cytoplasm, nucleus, extracellular fluid ions, sodium, potassium, channels electrode, voltmeter, microelectrode, resting potential millivolt (1/1000 volt) NERVE CELLS sodium channels, action potential axons, synapse, neurotransmitter, millisecond VIEWER SUBJECT Half-silvered mirror How an OPHTHALMOSCOPE works Optic Disc Fovea RETINAL PROPERTY 1 Image upside down 2 image is very small 3 image on a curved surface 4 TWO retinas 5 blood-vessel tree PERCEPTION >>>>> >>>>> seen right way up world seen actual size >>>>> no curve seen >>>>> only ONE world seen >>>>> no tree seen!!! RETINAL PROPERTY PERCEPTION 1 Image upside down >>>>> seen right way up 2 image is very small >>>>> world seen actual size 3 image on a curved surface >>>>> no curve seen 4 TWO retinas >>>>> only ONE world seen 5 blood-vessel tree >>>>> no tree seen!!! 6 BLIND SPOT (where the nerve comes in ) has no receptors >>>>> 7 only the central part of the retina is very sensitive >>>>> no hole seen! no difference in clarity between vision in different parts of the field Filling in Visual memory test: what letters are on the ‘4’ key? So: visual input is poor visual memory is poor therefore vision is poor! We are almost blind!! Sometimes: we see what is not there do not see what is there (Do we ever see what IS there?! There might be more to this perception thing than meets the eye..) Adaptation .. than this one. .. than this one. This one appears brighter... This one appears dimmer... Under PHOTOPIC CONDITIONS but under SCOTOPIC CONDITIONS Structure of eye and retina STRUCTURE OF THE EYE lens retina pupil EXPANDED VIEW cornea blind spot optic nerve retinal ganglion cell bipolar cell photoreceptor LIGHT to the blind spot where this fibre will become part of the optic nerve inner layer middle layer outer layer The eye and its optics 4 - 1 cone Rod RECEPTIVE FIELD: the area in which energy will have an effect VISUAL RECEPTIVE FIELD: the area in the outside world where light will have an effect THE VISUAL RECEPTIVE FIELD OF A SINGLE PHOTORECEPTOR The Visual Receptive Field of a single photoreceptor. Light outside this region will have no effect on this cell. screen a single rod The foveal pit Different shape Different distribution edge BLIND FOVEA SPOT edge edge BLIND FOVEA SPOT edge starts off bad BAD BAD Different sensitivity starts off better than rods gets very good doesn't improve much GOOD GOOD time in dark time in dark GOOD RODS Different pigments BAD BLUE GOOD CONES RED BAD RODS BLUE CONES RED STRUCTURE OF THE EYE lens retina pupil EXPANDED VIEW cornea blind spot optic nerve retinal ganglion cell bipolar cell photoreceptor LIGHT to the blind spot where this fibre will become part of the optic nerve inner layer middle layer outer layer The eye and its optics 4 - 1 RETINAL GANGLION CELLS