75. Detection, transmission and processing of the information in the retina. Central neurophysi-ology of vision. Light and dark adaptation. Visual acuity. Color vision.
Topic 75 of 80 in the MU Plovdiv syllabus for Human Physiology (Medicine, Year 2). The free AceMed note covers it in 9 sections, about 1,783 words (12 min of reading), with 39 flashcards.
In this note
Visual receptors. Light transduction mechanisms. Organization of the retinal neural network.
Visual Receptors
Light Transduction Mechanisms
Organization of the Retinal Neural Network
Organization of the retinal neural network
Central processing of visual information. Light adaptation. Visual acuity.
Light Adaptation
Visual Acuity
Recap Questions
Visual Receptors
The retina contains photoreceptors, interneurons (bipolar cells, horizontal cells, and amacrine cells), and ganglion cells. Visual receptors, rods and cones, are located in the innermost part of the retina, specifically the photoreceptor layer. They differ in shape, pigment, distribution, and organization, leading to functional differences.
Rods have low thresholds, are sensitive to low-intensity light, and function well in darkness. They do not participate in color vision and have low acuity. Cones have a higher threshold for light and operate best in daylight. They provide higher visual acuity and participate in color vision.
The human eye contains approximately 120 million rods and 6-7 million cones, with 1 million ganglion cells.
Rods are distributed throughout the retina except for the fovea, while cones are concentrated in the fovea, the central point of the retina responsible for sharp central vision.
Because the distribution of cones is central, our visual field for color is narrower.
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