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7 Cards in this Set
- Front
- Back
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What are the 2 special sensory organs discussed in lecture? |
Sight (the eye) Hearing (the ear) |
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Describe the anatomy of the eye |
Conjunctiva: outer layer of the eye Cornea: (fibrous tunic) mostly collagen, but is clear/transparent. Sclera: white tissue, continuous with the cornea. Anterior cavity: filled with aqueous humor, located in between the cornea and lens. Has 2 chambers: anterior & posterior, which are separated by the iris (colorful part). Iris: has dialator pupilae (back side of iris which dilates the pupil) and the sphincter pupilae (which constricts the pupil). Lens: consists of proteins called crystallines, clear. Uses to focus on an image, changes shape/bends for sight. Optic disc/blind spot: contains no photoreceptors & does not respond to light. Maculla: "sweet spot" near retina where images are put into focus. Vitreous humor: behind lens, jelly-like, mostly clear, helps hold retina in place. Choroid: (vascular tunic) black, behind vitreous humor. Retina: (nervous tunic) location of photoreceptors, nervous tissue. Contains Rods & Cones. Has 3 layers, photoreceptive layer: contains both rods & cones, fires. Bipolar layer: doesn't fire. Ganglionic layer: doesn't fire. |
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What are Rods and Cones? |
Rods and Cones are bipolar neurons/photoreceptive cells that are sensitive to stimulation from visible light. Rods: are involved in non-color vision, under conditions of reduced light. Contain Rhodopsin photopigment. Have larger receptive field. Cylindrical, with no taper from base to apex. (120 million) Cones: are involved in color vision & visual acuity (HD) and require bright light to function. Contain red, blue, green photopigments. Have smaller receptive field. Conical, tapers slightly from base to apex. (6-7 million, not evenly distributed around retina, located mainly around maculla) |
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What is a photopigment? |
Proteins lining rods and cones. Rods- rhodopsin Cones- red, blue, green |
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Compare and contrast the anatomy & physiology of Rods and Cones |
Rods: contain Rhodopsin, which consists of the protein Opsin and Retinal (vit.A). Retinal alternates between 2 shapes, depending on exposure to light. Na+ ion channels are located in the outer membrane of the Rod cell. Light and dark adaptation is accomplished by changes in the amount of available Rhodopsin. Starts out in the dark, firing. Rhospsin will change shape (retinal changes shape) when light strikes it. Then it will become loose from the Opsin (detaches), changing shape of the Opsin, which deactivates enzyme (cGMP) and closes the NA+ gated channels, causing it to stop firing. "Bleaching the photopigment" Cones: contain Idopsin, which consists of the protein Opsin and Retinal (vit.A). 3 major types of Opsin exist: red, blue & green. These function like Rhodopsin, however each Idopsin is sensitive to a much narrower spectrum of light. *cones and rods pair our neurotransmitters (Glutamate) which is inhibitory. * dendrites of rods & cones point away from the stimulus. When stimulated by light, they stop firing. When light hits photoreceptor, their not firing. * Vis. Phys. is totally backwards. |
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Describe the process by which light is converted into A.P.'s of the optic nerve |
As light, representing a certain color, strikes the retina, all cone cells containing photopigments capable of responding to that wavelength generate A.P.'s. Occurs in photoreceptors: rods and cones synapse with bipolar cells, which in turn synapse with ganglion cells, which form the optic nerves. Light enters the eye thought the retina which is composed of 2 photoreceptors (rods and cones). The conversion is made possible by the pigments located on the discs of the rods and cones. When light strikes these pigments, they change form causing a cascade of chemical reactions in the photoreceptors. These reactions make the membranes of the photoreceptors less permeable to certain ions such as sodium. This change alters each photoreceptors membrane potential and allows it to send nerve signals to cells in the next layer of the retina. Neurotransmitter release: Glutamate is inhibitory in the retina and excitatory in most other places. |
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What is the visual spectrum? |
Not very big, we don't have the ability to see every color. If we dont have the photoreceptor for it, we dont see it. |
