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The eye of the crepuscular rodent rock cavy
The eye of the crepuscular rodent rock cavy

... organization of neural circuits related to the retinal resolution or detection of changes in the levels of luminance (LAND, 2009; LAND and NILSSON, 2012). The quality of the optical system may limit the amount of information that can be made available to the brain since the retina can only encode in ...
C. elegans neuronal regeneration is influenced by life stage, ephrin signaling, and synaptic branching
C. elegans neuronal regeneration is influenced by life stage, ephrin signaling, and synaptic branching

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PTERYGOPALATINE FOSSA. Learning Objectives. • At the end of
PTERYGOPALATINE FOSSA. Learning Objectives. • At the end of

... In the upper part, the perpendicular plate lying between the maxilla and the medial pterygoid plate bifurcates; one limb remains attached to maxilla, while the other limb passes back to articulate with the sphenoid. Between these two bifurcating limbs lies the sphenopalatine foramen. ...
to view and/or an annotated lecture on macular
to view and/or an annotated lecture on macular

... The macula has the highest density of photoreceptors (rods and cones) and therefore gives us our best vision. The fovea even more so. Underneath the color photograph of the retina above is a cross section of the retina and underlying layers at a cellular level. You can see the multiple layers of th ...
Hydrogels for 3D Culture of Human Corneal Cells
Hydrogels for 3D Culture of Human Corneal Cells

... The cornea is the outermost layer of the eye and its purpose is to protect the eye from external environment. It is an avascular and transparent layer that is constructed from connective tissue and provides optical interphase to the visual system. (DelMonte & Kim 2011; Ghezzi et al. 2015) The cornea ...
Biological glass: structural determinants of eye lens transparency
Biological glass: structural determinants of eye lens transparency

... is perhaps unexpected. The explanation for this apparent paradox is that at very high protein concentrations, short-range-order interactions between lens proteins virtually eliminate light scatter through the process of destructive interference [6]. Light scattering in biological tissue occurs at bo ...
Introduction to Retinal Vascular Disease
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Harrison`s Principles of Internal Medicine, 16 Edition
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Full Text of
Full Text of

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Comparison of endothelial cell loss after cataract surgery
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VIEW PDF - Glaucoma Today
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Response Characteristics of Single Cells in the Monkey Superior
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... 1, response from contralateral eye only; 2, strong contralateral preference; 3, weak contralateral preference; 4, equal responses from both eyes; 5, weak ipsilateral preference; ...
The use of optical coherence tomography in neuro
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... OCT can be used to confirm a chronic optic neuropathy but does not usually give information on the underlying cause. PRNFL thinning is an objective biomarker of optic atrophy. Notably, optic atrophy takes about 6 to 8 weeks to develop after an acute insult.7 Thus, immediately after an acute severe t ...
PDF
PDF

... stopped fixating. The results were the same in both cases. During this condition, eye movement records showed that the monkey made apparently random fixations, unassociated with the timing of events in the trial and with no tendency to cluster in any one location. The monkey appeared to ignore both ...
Diagnosis of Pupillary Disorders
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... off. A practical alternative is to use a separate, weak light source to illuminate both eyes at a tangential angle from below, so that both pupils are visible and a minimum area of retina is being illuminated in each eye. It is best not to look at the eye with the brighter stimulus, since this cause ...
Light and Everything Lab Manual
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... the spectrum projected on white, gray, or black surfaces, and the reconstitution of the refracted light into a single point. In Lab 7, we use a bigger spectrum, produced in a dark room, to observe the appearance of variously colored objects in different regions in the ...
Optical Coherence Tomography and Advanced Fundus Imaging
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... tissues or between probe, coupling medium and tissues, OCT does not require any contact with the eye (thus avoiding the potential for tissue compression and/or distortion) and it allows measurement of structures and distances on the sub- 10 micron scale, versus the 100micron scale of all but the hig ...
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A mathematical description of nerve fiber bundle trajectories

... real variability in the wiring of the human retina have to be considered. One possible source of variability is the choice of our basic equation used to describe individual nerve fiber trajectories, Eq. (1). We started our modeling with Taylor polynomials. It turned out that most fibers could be ea ...
牂楡獮整m
牂楡獮整m

... which is located in the dorsolateral portion of the pons (in a position analogous to that of the posterior column nuclei in the medulla). The axons of the second neurons cross the midline and ascend in the contralateral medial lemniscus to the ventral posteromedial nucleus of the thalamus (VPL). Th ...
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Topography and Structure of Corpus striatum in Insectívora

... is formed by an oval group of cells situated on the ventral aspect of the putamen. The boundary between the putamen and the Na are rot numerous fascicles of fibres running horizontally from the anterior commissure to the external capsule. At this level the cells of the ventral part of the caudate nu ...
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... to a specific type of sensory information, such as light or chemical molecules. Reception is the process of detecting and responding to incoming sensory information. Every receptor cell within a sensory system has an area of sensitivity. This is called its receptive field. A receptive field is the a ...
The Zeaxanthin and Atrophic AMD Visual Function Study
The Zeaxanthin and Atrophic AMD Visual Function Study

... Following FDA and DVA IRB/Human Subjects approval in early December 2007, some (n=53 patients) of 60 patients have completed the Informed Consent process, enrolled in ZVF, and completed their 1st Baseline Evaluation. We present available demographic, symptom, visual function and ocular descriptive d ...
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... found to be increased in populations with hypertension independent of glycaemic risk, obesity or lipids [1]. We don’t know how generalisable this finding is. • Glaucoma: Nocturnal hypotension is also found to be associated with progression of visual field defects in glaucoma. • Late stage AMD: Some ...
l0: fibers from the contralateral pontine nuclei, and the inferior
l0: fibers from the contralateral pontine nuclei, and the inferior

... There are scattered stellate cells in the superficial part of the molecular laver whose dendrites are contacted by axons of granule cells. Axons of stellate cells synapse mainly with furkinje cell dendrites; a few enter the innermost cortical layer and establish a feedback circuit bv synapsingwith g ...
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Photoreceptor cell



A photoreceptor cell is a specialized type of neuron found in the retina that is capable of phototransduction. The great biological importance of photoreceptors is that they convert light (visible electromagnetic radiation) into signals that can stimulate biological processes. To be more specific, photoreceptor proteins in the cell absorb photons, triggering a change in the cell's membrane potential.The two classic photoreceptor cells are rods and cones, each contributing information used by the visual system to form a representation of the visual world, sight. The rods are narrower than the cones and distributed differently across the retina, but the chemical process in each that supports phototransduction is similar. A third class of photoreceptor cells was discovered during the 1990s: the photosensitive ganglion cells. These cells do not contribute to sight directly, but are thought to support circadian rhythms and pupillary reflex.There are major functional differences between the rods and cones. Rods are extremely sensitive, and can be triggered by a single photon. At very low light levels, visual experience is based solely on the rod signal. This explains why colors cannot be seen at low light levels: only one type of photoreceptor cell is active.Cones require significantly brighter light (i.e., a larger numbers of photons) in order to produce a signal. In humans, there are three different types of cone cell, distinguished by their pattern of response to different wavelengths of light. Color experience is calculated from these three distinct signals, perhaps via an opponent process. The three types of cone cell respond (roughly) to light of short, medium, and long wavelengths. Note that, due to the principle of univariance, the firing of the cell depends upon only the number of photons absorbed. The different responses of the three types of cone cells are determined by the likelihoods that their respective photoreceptor proteins will absorb photons of different wavelengths. So, for example, an L cone cell contains a photoreceptor protein that more readily absorbs long wavelengths of light (i.e., more ""red""). Light of a shorter wavelength can also produce the same response, but it must be much brighter to do so.The human retina contains about 120 million rod cells and 6 million cone cells. The number and ratio of rods to cones varies among species, dependent on whether an animal is primarily diurnal or nocturnal. Certain owls, such as the tawny owl, have a tremendous number of rods in their retinae. In addition, there are about 2.4 million to 3 million ganglion cells in the human visual system, the axons of these cells form the 2 optic nerves, 1 to 2% of them photosensitive.The pineal and parapineal glands are photoreceptive in non-mammalian vertebrates, but not in mammals. Birds have photoactive cerebrospinal fluid (CSF)-contacting neurons within the paraventricular organ that respond to light in the absence of input from the eyes or neurotransmitters. Invertebrate photoreceptors in organisms such as insects and molluscs are different in both their morphological organization and their underlying biochemical pathways. Described here are human photoreceptors.
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