The Membrane Of The Cone Cells

 A.accommodation B.the concentration of cones in the fovea C.chemical structure of the vitreous humor D.the prevalence of amacrine cells in the

Retinitis pigmentosa is a group of inheritable diseases that is characterized by gradual deterioration of the photoreceptors in the retina. The photoreceptor cells in the retina, rod cells, are light sensitive cells that are able to sense low levels of light. The frequency of retinitis pigmentosa is one in four thousand births (Deng et al., 2015; Fahim et al., 2012; Haddad et al., 2016; Shu et al., 2012) People affected by retinitis pigmentosa will typically exhibit symptoms of night-blindness first, and this will precede a loss in the patient’s visual acuity field that starts from the outer edge and gradually moves inward resulting in a much smaller visual field and loss of peripheral vision, also known as tunnel vision (Haddad et al., 2016).

However, at its head, there is a blind spot because there are no photoreceptors in this part of

Dugesia spp., also known as planaria is a small flat dark brown worm of varying sizes around 0.3 – 2 cm long and 1 – 2 mm wide (Palmer and Fowler, 1975 as cited by Cha, 2001). Although they are small, they are hermaphroditic (Maule, 2006). The middle of the body is darker in color with tiny spots. The body consists of an arrow shaped head and a long unsegmented body that narrows as it reaches the posterior end (T. Huang, biology student, personal communications). Midway down the ventral side of its body, the pharynx is a tube-like structure that protrudes out for feeding (Cha, 2001). The body is smooth and stretches in contracting and expanding movements as the Dugesia spp. travels around a flat surface (T. Huang, biology student, personal communications). The two side parts of the arrow that extends out of its head are sensory organs, the auricles (Cha, 2001). The auricles help sense water currents so that the Dugesia spp. is aware of the direction of water flow (Kriska and Gyorgy, 2013). Dugesia spp. has tiny eyes called eyespots located on the dorsal side of its arrow head. The eyespots can detect light and are extremely sensitive to light (Cha, 2001).

This paper considers that focused primarily on human iris. This choice of this topic was made due to interest of wanting to provide knowledge about the factors that determine eye color. I know, like hair or skin, brown eyes are dominant over blue eye genes. I also know that a person can be identified by the retina scanners because everyone has their iris with unique structural patterns.

The smooth ER does not have any ribosomes on it's membrane. It's functions can vary depending on the differences of the cell it is located in. The smooth ER makes lipids, breaks down carbohydrates, and detoxifies substances that may be harmful to the cell.

Rhodopsin is a biological pigment which is extremely sensitive to light energy found in the rods of the retina and is said to be a G-protein-coupled receptor (GPCR). It was discovered that when rhodopsin is exposed to light energy, it immediately photobleaches.

In the case of the “off” center response, the Rod is not exposed to light and therefore, Rhodopsin does not absorb the light photon and the GPCR does not activated Transducin. For this case, since Transducin is not activated, there becomes an increase in intracellular [cGMP]. The cGMP molecules are able to bind to the cGMP-gated sodium channels subsequently causing a net flux of sodium inside the photoreceptor. This net influx causes a graded action potential to fire in the photoreceptor. This action potential fires down the cell causing an increase in NT release into the synaptic cleft. The NT transmitter involved is Glutamate, once again. This photoreceptor cells makes a synapse with the “on” center bipolar cell and extends over to the “off”

The rods, in contrast, are all identical to one another (Purves et al., 2001). At the lower intensities of light, only the rods are activated. However, as the amount of light entering the eye increases, so does the activity of the cones, ultimately influencing what an individual can see (Purves et al., 2001). Photopigments, which are found in both rods and cones within the retina, respond to light through a chemical process that releases energy. In order to detect varying levels of light, “photopigments consist of 11-cis-retinal (a derivative of vitamin A) bound to proteins called opsins, which modify the photopigments’ sensitivity to different wavelengths of light. Light converts 11-cis-retinal to all-trans-retinal, thus releasing energy that activates second messengers within the cell” (Kalat, 2013, p. 159). The photopigments are responsible for initiating the first steps of communication within visual system when levels of light are first

This type of convergence shown is called Center Surround Antagonistic (CSA) because three receptors converge onto one ganglion cell that can be deterred by the horizontal cells that make up the system. Parasol ganglion cells process black and white light information. Midget ganglion cells process colored light information. While we might think that colored light and the corresponding cells would dominate our vision this is only due to the high concentration in our fovea where most of the light entering our eye is directed to. Rods and parasol ganglion cells are most abundant in our retinal surface although it seems contradicting. After the light information coming into our eye is processed and converged through the layers in our retinal it is sent through the ganglion axon bundle that forms our optic nerve and crosses at the optic chiasm. The translated information crosses over each other so that sensory information from the left visual field is processed in the same area and vice versa for the right visual

The ERG is usually diminished in scotopic conditions and the cone response in bright light is markedly

(A–C) Photographs of a D. longipes specimen in dorsal (A and B) and ventral (C) view. The yellow-orange eyeshine in the upward-looking, tubular eyes (A and B) and the eyeshine from the diverticulum (C) is from the camera flash. The black structures beside the main eyes (A and B) are the upper surfaces of the diverticula.

The objective of this study is to investigate the molecular mechanisms responsible for non-image-forming visual responses, such as the coordination of the biological clock. Because retinal rod and cone cells are not required for non-image-forming visual responses, the researchers hypothesized that retinal ganglion cells (RGC) may be the light sensitive cells utilized in the non-image-forming visual response pathway. The researchers also hypothesized that if the RGCs are light sensitive, then the protein melanopsin, which is found on the surface of RGCs, is likely the photopigment that causes RGCs to respond to light.

To understand the applications of mantis shrimp vision; we must first understand how the eyes of the mantis shrimp work. The compound eye of the mantis shrimp is made up of many ommatidia; “an ommatidium is like a simple but complete photoreceptor organ consisting of optical components and receptor cells” Most research suggests that the vision experienced by the mantis shrimp is due to three distinct regions in its eye; there is an upper and lower hemisphere separated by the midband; these regions are made of distinct ommatidia; adapted and responsible for different functions in the eye of the mantis shrimp. The research I have come across suggests that the most important region is the modified midband because this is the