Term
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Definition
| The sense of smell is associated with olfactory receptor cells cells in the upper region of the nasal cavity. The ofactory receptor cells are confined to a yellowish brown patch of specialized epithelium, the olfactory epithelium. |
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Term
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Definition
| The olfactory receptor cells are bipolar neurons embedded in a layer of columnar epithelial cells, which have microvilli and are covered with a film of mucus. |
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Term
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Definition
| One end of the olfactory receptor cell protrudes slightly beyond the surface of the epithelium, and give rise to olfactory cilia, which form a dense mat on the surface. |
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Term
| Olfactory receptor proteins |
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Definition
| The olfactory cilia contain integral membrane olfactory receptor proteins that bind to, and thought to be recognized by up to a thousand different olfactory receptor proteins, coded by the same number of olfactory receptor genes. |
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Term
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Definition
| The other, more central, process of the olfactory receptor neuron consists of an unmyelinated axon that runs from the nasal cavity to the part of the brain called the olfactory bulb. Between 10 and 100 of these axons form a bundle surrounded by Schwann cell processes. |
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Term
Cribriform plate
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Ethmoid bone |
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Definition
| To reach the olfactory bulb, the axons pass through fine perforation in the cribriform plate of the ethmoid bone. |
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Term
| Generator potential: odor |
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Definition
| When a molecule binds to its olfactory receptor protein, it produces a generator potential that increases the rate of impulse firing of the receptor cell in proportion to the intensity of the stimulus. In this case, the intensity of the stimulus is determined by the number of molecules of odoriferous substance dissolved in the mucus covering the olfactory epithelium. |
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Term
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Definition
| in many animals, the nasal cavity contains a vomeronasal organ, which has a second kind of olfactory receptor cell believed to be sensitive to pheromones. |
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Term
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Definition
| used by mammals for signalling, particularly in sexual and territorial marking situations. |
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Term
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Definition
| the first site for olfactory information processing in the brain. |
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Term
Olfactory Glomeruli
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Mitral Cells |
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Definition
| The unmyelinated axons of olfactory receptor cells that respond to similar odor-producing compounds may converge in large numbers onto special structures called olfactory eruli, which are really complex synapses with dendrites of the mitral cells. |
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Term
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Definition
| Mitral cell axons exit the olfactory bulbs in the olfactory tracts, which terminate in the olfactory cortex. Information on odor is the directed to two different locations in the brain: The limbic system, Frontal lobes |
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Term
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Definition
| some regions of the olfactory cortex make connection with hipocampus and amygdala, both structures being components of the limbic system. These regions may be involved with emotional and memory-retrieving aspects of smells, perhaps influencing our behavior and thought processes. |
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Term
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Definition
| other regions of the olfactory cortex make connections with the frontal lobes via the thalamus. These regions are believed to be involved with the conscious perception of smell |
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Term
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Definition
| are modified epithelial cells, NOT neurons. Taste cells are bundled together in group of about 40-60 contained in a taste bud. Taste receptor cells die every 10 days, and are replaced by new taste receptor cells formed from cells called basal cells. |
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Term
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Definition
| The taste bud is embedded in the epithilium of the tounge and connected to the tongue’s surface by a taste pore. Microvilli or taste hairs extend from the apical surfaces of the taste receptor cells, and project through the taste pore to make contact with the saliva bathing the tounge. The plasma membranes of the taste hairs contain taste receptor proteins that bind to specific tasty molecules dissolved in the saliva. |
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Term
| At the base of each taste receptor cell |
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Definition
| there is a synaptic contact with a branch of an afferent nerve fiber. One afferent fiber may carry the signals from many receptors. These across taste chemicals either depolarize or hyperpolarize taste cells, so regulating neurotransmitter release from the taste cells. |
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Term
On the tongue, collection of taste buds occur in three different types of structures called papillae:
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Definition
-Circumvallate
-Foliate
-Fungiform |
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Term
| Humans classify tastes in five groups. |
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Definition
-bitter
-salty
-sweet
-sour
-unami |
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Term
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Definition
| a unique taste associated with protein-rich foods and produced by monosodium glutamate (MSG). THe unami receptor is an amino acid receptor. Since amino acids are essential for building proteins, the receptor is important in helping to identity and seek out these substances in the diet. Human unami receptor is most sensitive to monosodium glutamate, which is one the commonest amino acids in our diet and gives high-protein food a meaty, attractive flavor |
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Term
| Cranial nerves VII, IX and X to the medulla Gustatory Nucleus |
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Definition
| Signals from the taste buds in the tongue, epiglottis and esophagus travel via cranial nerve VII, IX, and X to the medulla where they synapse with neurons in the gustatory nucleus, which is also called the nucleus of the tractus solitarious From the medulla, signals passto the thalamus, which relays them to the post-central gyrus and insula of the cerebral cortex, close to the somatosensory area for the tongue |
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Term
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Definition
| respond to different colors of light, and are also able to signal the intensity of the light. Some preliminary processing of these signals takes place in the neural networks of the retina, which develops as an outgrowth of the neural tube. In some ways, the retina can be considered as a small brain. |
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Term
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Definition
| moved by the orbicularis oculi and levator palpebrae superioris muscles. The conjunctiva is a mucous membrane that lines the eyelids and extends over the anterior surface of the eye with the exception of the cornea. |
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Term
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Definition
| consists of the lacrimal gland located in the orbit and a series of tubes that convey the tear fluid into the nasal cavity. |
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Term
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Definition
| in the posterior part of the eye, the outer layer makes up the white of the eye, and is composed of dense fibrous connective tissue. The collagenous fibers in the sclera are not organized, and they scatter light so much that the sclera looks white. |
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Term
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Definition
| in the anterior part of the eye, the outer layer becoes the transparent window of the eye. The cornea is transparent because it has few cells and no blood vessels, and (unlike the sclera) the layers of collagenous fibers are so regularly arranged that very little scattering occurs as light passes through it. The cornea hase many naked nerve endings that transmit pain. That is why anything that touches your cornea causes a painful sensation. |
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Term
| Uveal layer (middle layer) |
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Definition
| typically highly vascular (that is, it contains many blood vessels). |
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Term
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Definition
| The posterior part of the eye, the uveal layer is called the chorid. The choroid contains numerous blood vessels and melanocytes. The melanocytes contain melanin granules, which assist in lprecenting light from being reflected around in the interior of the eye and confusing the image. The blood vessels of the choroid are very important in conveying nutrients to the retinal pigmented epithelium and neural retina |
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Term
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Definition
| In the aterior part of the eye, the choroid gives way to the ciliary body and the iris. The ciliary body has ciliary muscles and a series of foldings called ciliary processes, which are connected to the suspensory ligaments that hold the lens in position. |
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Term
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Definition
| are involved in altering the shape of the shape of the lens during accommodation. |
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Term
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Definition
| Cells in the ciliary body are responsible for secreting the aqueous humor |
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Term
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Definition
| the retina consists of the neural retina and non-neural retina or pigmented epithelium (=retinal pigmented epithelium) |
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Term
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Definition
| is a single layer of melanin-containing cells that is sandwiched betweed the neural retina and the choroid. The pigmented epithelium is very important in regulating the passage of nutrients from the choroidal blood into the retina, in participating in the metabolism of vitamin A and its derivatives, and in removing fragments of membranes that have been shed by the photoreceptor cells. |
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Term
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Definition
| forms in the embryo as an outgrowth of the brain. Its primary function is to detect light, and therefore the neral retina acts like the film in a camera. It does more than a film, however, because its neronal networks also carry out a preliminary analyisis of the spatial patterns and movement of the image. It relays this information to the brain via the optic nerve. |
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Term
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Definition
| are neurons that relay signals from the photoreceptors to the ganglion cells |
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Term
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Definition
| are neurons with axons that exit for the posterior part of the eye, and form the optic nerve. The optic nerve carries signals (action potentials) from the retina to the brain. |
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Term
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Definition
| are neurons that are involved in lateral interactions between the above cell types |
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Term
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Definition
| are neurons that are also incolved in lateral in interactions between the above cell types. Lateral interactions can be responsible for certain illusions, such that seen in the Herman Grid. |
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Term
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Definition
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Term
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Definition
| The cone photoreceptors are concentrated in a central part of the retina called the yellow spot or macula lutea. It looks yellow it a mixture of zeaxanthin and lutein. Both are derived from the diet and are related to beta-carotene. They may have a protective function. In the center of the macula lutea is a depression called the fovea. This is the area of sharpest visual acuity in the retina. |
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Term
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Definition
| The point at which the optic nerve fibers exit the retina is called the optic disk. Blood vessels also enter the eye at this point, and nourish the inner surface of the retina. Because there are no photoreceptors at the optic disk, this area is called the blind spot. |
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Term
| Chambers and Cavities of the eye |
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Definition
| The eye is divided into anterior cavity and posterior cavity by the lens. Additionally, the anterior cavity is is divided into anterior chamber, which lies anteriorly to the iris, and the posterior chamber, which lies behind the iris. |
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Term
| Aqueous humor Canal of Schlemm |
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Definition
| a watery fluid which secreted into the posterior chamber by the ciliary body. The aqueous humor flows through the the aperture of the iris into the anterior chamber and then out of the eye into the blood by a channel called the canal of Schlemm. |
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Term
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Definition
| Factors that increase the secretion of acqueous humor or block its outflow cause an increase in the intraocular pressure. This occurs in the condition called glaucoma, which can lead to blindness due to retinal degeneration. |
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Term
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Definition
| the posterior cavity of the eye is filled with a transparent, jelly-like body called the vitreous humor. |
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Term
| Refraction of light through the light |
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Definition
| In the eye, an image of the external scene must be formed on the light-sensitive layer of the retina. In a camera (where the film replaces the retina), this is done by the lens. In the eye, however 75% of the refractory power is due to the cornea, only about 25% being due to the lens. |
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Term
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Definition
| The lens of the eye function to adjust the refracting power of the eye so that images are always sharply focused on the retina irrespective of the distance of the object being viewed. This process of adjusting the power of the lens depending on whether we are viewing a near or distant object is called accommodation. |
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Term
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Definition
| The lens assumes a more powerful, spherical shape because the muscles in the ciliary body contract. This reduces the pull on the suspensory ligaments and allows lens to round up because of its natural elasticity. This increases the refractive power of the lens. |
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Term
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Definition
| The lens becomes more flattened and therefore weaker because the muscles in the ciliary body relax. This increases the pull on the suspensory ligaments, which in turn pull on the lens and flatten it. This reduces the the refractive of the lens. |
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Term
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Definition
| as a person ages, the natural elasticity of the lens is lost and it is unable to assume the spherical shape necessary for viewing near objects. Objects such as the printed page tend to be dled further away from eyes, because the lens cannot be made powerful enough to bring them into focus if they are held closer. The eye is then said to prebyopic and requires the assistance of a convex lens to increase the power of the eye and focus near objects of the retina. |
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Term
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Definition
| farsightedness caused by the eyeball being a little too short, and the light rays converge towards a point behind the retina. As with presbyopia, a convex lens is needed to increase the power of the eye and correct the problem |
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Term
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Definition
| nearsightedness, because the eyeball is a little too long, and light rays are focused in front of the retina. A concave lens is needed lens is needed to decrease the power of the eye and correct the problem. |
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Term
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Definition
| most often caused by irregular curvature of the cornea. A person with astigmatism might be able to bring vertical lines into focus, but horizontal lines become blurred (viceversa) A cyclindrical lens can sometimes correct the problem. The cylinder below is exaggerated - normally, a cylindrical lends in prescription glasses is not noticeable unless you look through the lens and carefully rotate it. |
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Term
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Definition
| a condition where the lens loses its transparency and becomes opaque, either partially or completely. Cataract can be caused by a variety of factors, including chemical agents, ultraviolet and infrared radiation. |
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Term
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Definition
| In rods, the visual pigment is reddish in color and is called rhodopsin The visual pigment rhodopsin consists of an integral, transmembrane protein called opsin that has bound to it the aldehyde of vitamin A which is called retinal. |
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Term
| When rhodopsin absorbs light |
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Definition
| it is changed chemically. The chemical change involves staightening out the bent molecule of 11-cis retinal to form all-trans retinal. The protein part of the rhodopsin molecule (opsin) then changes its shape and is activated. |
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Term
| When activated by the of light |
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Definition
| rhodopsin initiates a series of events that lead to membrane hypolarization |
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Term
| The ultimate result of photoreceptor membrane hyperpolarization |
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Definition
| is an increase in the firing rate of the ganglion cells, which transmit action potential up to the lateral geniculate nucleus of the thalamus |
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Term
| light-activated rhodopsin has the following actions... |
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Definition
a) it interacts a G protein called transduction
b) this causes activation of an enzyme called cyclic GMP phosphidiesterase
c) This breaks down cGMP, reducing its amount in the photoreceptor
d) Reduction in the amount of cGMP causes closure of sodium (and calcium) channels in the plasma membrane and hyperpolarization of the cell membrane the signal from bleached rhodopsin is then turned off by phosphorylation (by an enzyme rhodopsin kinase). The phosphorylated rhodopsin is then inactivated by a protein called arrestin. |
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Term
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Definition
| have normal color vision, and can match all colored lights with a mixture of red, green, and blue light |
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Term
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Definition
| (nearly alway males), need only two colors to match any color or white light. There are three types: protanopes, deutranopes, and tritanopes |
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Term
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Definition
| are dichromats who can match all colors with green and blue. They are insensitive to red light, and confuse reds, yellows, and greens, which look the same to them |
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Term
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Definition
| are dichromats who can match all colors with read and blue. They also confuse reds, yellows and greens. |
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Term
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Definition
| are rare dichromats who can match all colors with red and green. They are insensitive to blue light. |
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Term
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Definition
| are people who cannot distinguish colors at all, they are truly color blind, and can match any two colored lights simply by adjusting their intensities. |
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Term
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Definition
| Much of the increase in sensitivity of the eye in dim light is due to the regeneration of rhodopsin molecules that hace been bleached in the daylight outside. The process involves the pigment epithelium, which converts the all-trans isomer back to 11-cis and returns it to the retina |
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Term
| Dark Adaption (all-trans retinal) |
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Definition
| In the rod outer segment, bleached rhodopsin releases all-trans retinal, which is promptly reduced to all-trans retinol (vitamin A) The all-trans retinol leaves the rod out segment and passes into the pigment epithelium. it is them isomerized back to 11-cis retinol, converted to 11-cis retinal, and transported to the rod out segment. In the rod out segment 11-cis retinal combines with opsin to regenerate rhodopsin. the above process is sometimes called the “visual cycle" |
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Term
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Definition
| One important aspect of this integration of visual information is that information from both eys is used in the perception of depth and distance. This is called binocular vision or stereoscopic vision |
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Term
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Definition
| Just anterior to the pituitary gland, the optic nerves from the X shaped optic chiasma. Within the optic chiasma some fibers cross over. That is, there is partial decussation of the fibers. |
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Term
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Definition
| Fibers from the left visual field (nasal half of the eye, temporal half of the right eye retina) are segregated to from the right optic tract. |
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Term
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Definition
| Fibers from the right visual field (temporal half of the left eye, nasal half of the right eye) are segregated to form left optic tract. |
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Term
| Visual cortex optic radiations |
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Definition
Neurons in the lateral geniculate nucleus send their axons to the visual cortex (in the posterior occipital lobe) along prominent nerve tracts called the optic radiations.
-An object in the left visual field therefore activates in the right occipital cortex.
-An object in the right visual field therefore activates neurons in the left occipital cortex. |
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Term
| The usefulness of this arrangement |
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Definition
| is that if we need to bat away a bee approaching from the left, the information about the bee in our left visual field arrives in the right cerebral cortex, which controls the left hand. So we do not have to wait for information to be transferred from one half of the brain other via the corpus callosum. |
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