Term
|
Definition
| process by which the eyes detects light energy |
|
|
Term
| rods and cones contain visual ________ |
|
Definition
| pigments(photopigments). arraanged in a disklike infoldings of the plasma membrane that can change shape as they absorb light |
|
|
Term
| give me description of rods |
|
Definition
| sensitive to dim light and best suited for night vision. absorb all wavelengths of visible light |
|
|
Term
|
Definition
| process by which the eyes detects light energy |
|
|
Term
| rods and cones contain visual ________ |
|
Definition
| pigments(photopigments). arraanged in a disklike infoldings of the plasma membrane that can change shape as they absorb light |
|
|
Term
| give me description of rods |
|
Definition
| sensitive to dim light and best suited for night vision. absorb all wavelengths of visible light. sum of visual input from many rods feed into a single ganglion cell. results in fuzzy and indistinct images |
|
|
Term
| give me a description of cones |
|
Definition
| needs bright light for activation, lower sensitivity. have pigments that furnish a vividly colored view. each cone synapses with a single ganglion cell. vision is detailed and has high resolution. |
|
|
Term
| How do photoreceptors translate incoming light into electrical signals? |
|
Definition
| there is a light absorbing molecule called retinal that combines with a protein named opsin. it is similar to and synthesized from vitamin a. |
|
|
Term
| how do the excitation of rods work? |
|
Definition
| 1. retinal from vitamin a combined with opsin turns to rhodoopsin. 2. light absorbtion by rhodoopsin triggers a rapid series of steps in which retinal changes shape and eventually releases from opsin. 3. pigment regeneration - enzymes slowly convert all trans-retinal to its cis form in cells of its pigmented layer, needs atp. |
|
|
Term
| Whats the process of the excitation of cones? |
|
Definition
| visual pigments are similar to rods(retinal + opsin) . three type of cones : blue, green and red. intermediate colors are perceived by activiation of more than one cone. method of excitation is similar to rods. |
|
|
Term
| whats the process of phototransduction? |
|
Definition
| 1. light energy transforms cis-retinal to all trans-retinal releasing activated opsin. 2. the freed opsin activates a g protein called transducin. 3. transducin catalyzes activation of phospodiesterase(PDE). 4. Phosphodiesterase hydrolyzes cGMP to GMP and releases it from sodium channels. 5. without bound cGMP, sodium channels close, therefore closing sodium channels hyperpolarizing and neurotransmitters cant be released. |
|
|
Term
| what happens when one light passes from one transparent medium to another? |
|
Definition
| it speed changes and refracts(bends),.light passing through a convex lens (as in the eye) is bent so that the rays converge to a focal point. |
|
|
Term
| what is the sequence of light passing from air to eye? |
|
Definition
| It starts from the cornea, aqueous humor, lens, vitreous humor, and the neural layer of the photoreceptors. |
|
|
Term
| light is refracted in which location? |
|
Definition
| at the cornea, entering the lens and leaving the lens. |
|
|
Term
| how does fine focusing work? |
|
Definition
| the lens and the curvature allow it for fine focusing of an image |
|
|
Term
| looking at far distance for proper focusing needs what? |
|
Definition
|
|
Term
| what does far point of vision mean? |
|
Definition
| the distance beyond which the lens do not need to change shape to focus(about 20ft) |
|
|
