chapter 15 special senses part 4 - vision and how light effects sight
Terms : Hide Images
| 262363514 | Light | Visible light, refraction, convergence, focal point, focusing; lens changes shape causing adjustment of focal point on retina | |
| 262363515 | Visible Light | portion of electromagnetic spectrum detected by human eye | |
| 262363516 | Refraction | bending of light | |
| 262363517 | Convergence | light striking a convex suface | |
| 262363518 | Focal Point | point where light rays converge and cross | |
| 262363519 | Focusing | causing light to converge; emmetropia and far point of vision |  |
| 262370654 | Emmetropia of Focusing | normal resting condition of lens; Ciliary muscle is relaxed, lens is flat | |
| 262370655 | Far Point of Vision of Focusin | point at which lens does not have to thicken to focus; 20 feet or more from eye | |
| 262370656 | Near Point of Vision | closer than 20 feet; Changes occur in lens, size of pupil, and distance between pupils; Accommodation, pupil constriction, convergence | |
| 262370657 | Accommodation of Near Point Vision | ciliar muscles contract due to parasympathetic input via cranial nerve III; PUlls choroid toward lens reducing tension on suspensory ligaments; Lens becomes more spherical, greater refraction of light | |
| 262370658 | Pupil Constriction of Near Point Vision | varies depth of focus | |
| 262370659 | Convergence of Near Point Vision | as objects move close to eye, eyes are rotated medially; reflex contraction of medial rectus muscle | |
| 262370660 | Structure of Retina | Sensory retina, Pigmented retina |  |
| 262370661 | Sensory Retina | 3 layers of neurons: photoreceptor, bipolar, ganglionic; Cell bodies form nuclear leayers separated by plexiform layers, where neurons of adjacent layers synapse with each other | |
| 262370662 | Pigmented Retina | single layer of cells; filled with melanin; With choroid, enhances visual acuity by isolating individual photoreceptors, reducing light scattering | |
| 262370663 | Rods | bipolar photoreceptor cells; Black/Wht vision; Found over most of retina, but not in fovea; More sensitive to light than cones | |
| 262370664 | Rhodopsin of Rods | is a protein that changes shape when struck by light; eventually separates into its 2 components: opsin & retinal; Retinal can be converted to Vit A from which it was originally derived; In absence of light, opsin and retinal recombine to form rhodopsin | |
| 262370665 | Rods Sensory Cells | unusual sensory cells: when not stimulated they are hyperpolarized; light causes them to depolarize; Depolarization of rods causes depolarization of bipolar cells causing depolarization of ganglion cells | |
| 262370666 | Light and Dark Adaptation | Adjustment of eye to changes in light; Happens because of changes in amount of available rhodopsin; Rods and Pupils | |
| 262370667 | Photoreceptors Picture |  | |
| 262370668 | Rods in Light/Dark Adaptation | in bright light, more rhodopsin broken down into Vit A, protecting eye and making it less sensitiv to light; In darker conditions, more rhodopsin produced so eye is more sensitive to light; Takes eyes a while to accommodate when going from dark to light and vice versa because of these chemical changes that must occur | |
| 262370669 | Pupils in Light/Dark Adaptataion | constriction in bright light; dilation in dim light | |
| 262370670 | Cones | bipolar receptors; Responsible for color vision and visual acuity; Numerous in fovea and macula lutea, fewer over rest of retina; As light intensity decreases so does our ability to see color; contains iodopsin |  |
| 262370671 | Iodopsin in Cones | visual pigment; 3 types that respond to blue, red and green light; Overlap in response to light, thus interpretation of graduation of color possible; several millions | |
| 262370672 | Inner Layers of Retina | Rods and cones synapse w/bipolar cells that synapse with ganglion cells inall areas except fovea; Ganglion cell axons converge at optic disc (except infovea centralis) then exit via optic nerve then impulses travel to visual cortex; | |
| 262370673 | Fovea Centralis of Inner Layer | highest visual acuity | |
| 262370674 | Rods of Inner Layer | spatial summation; one bipolar cell receives input from numerous rods, one ganglion cell receives input from several bipolar cells | |
| 262370675 | Cones of Inner Layer | exhibit little or no convergence | |
| 262370676 | Neuronal Pathways 1-5 | 1)each visual field divided into temporal and nasal half 2)after passing through lense, light from each half projects to opposite side of retina 3) optic nere consists of axons extending from retina to optic chiasm 4) in optic chiasm, axons from nasal part cross and project to opposite side of rain, axons from temporal part do not cross 5) optic tract consists of axons that have passes through optic chiasm to thalamus |  |
| 262370677 | Neuronal Pathways 6-8 | 6)axons synapse in lateral geniculate nuclei of thalamus, collateral branches of axons in optic tracts synapse in superior colliculi 7) optic radiation consists of axons from thalamic neurons that project to visual cortex 8) right part of each visual field (drk green/drk blu) projects to left side of brain, left part of each visual field (lght grn/ lgt blu) projects to right side of brain | |
| 262370678 | Visual Fields | Binocular vision: visual fields partially overlap yielding depth perception |  |
