Rod+Cells+-+TS

= Introduction = toc Picture this. You are outside and it is around 9:45. You look up into the sky there are millions and billions of stars. You are seeing these stars with a cell in your **retina** called **rod** cells. The human eye has several important parts and the part that allows us to handle seeing in low light are special cells called the **rods**. Rods are located in the **retina tissue** which lines the back of the human eye. The rods are an important part of the structure of the human eye. Without the rods, human vision would not work. Unfortunately, these special cells do not always work because of various diseases, the most prevalent one being ** retinitis pigmentosa. **

= The Structure =

The human eye is a complicated structure. All the parts of the eye work together with our brain to complete a picture. Light enters through our **pupil**, and splashes on the retina where special cells called rods and **cones** allow us to see colors and black and white.The pupil is important it decides how much light is let into the eye. Rods and cones are called **photoreceptors.** Photoreceptors are structures in a **living organism**, especially a sensory cell or sense organ that responds to light falling on it. Rods work best in dim light and are concentrated on the edges of the retina. Cones differ from rods because cones work best in bright light and are concentrated in the center of the retina. Cones handle color vision and detail while on the other hand, rods handle shadows and dim light. Once the cells gather the light, a message is sent to our **brain** throug h the optic nerve.The ** optic nerve ** is transmitting impulses to the brain from the retina at the back of the eye. The brain then signals what it is that we are seeing. media type="youtube" key="jnTLcj6BDKE" width="913" height="421" align="left"

= = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = =This video shows the structure of the rods and the cones. One fact I learned from this video is both rods and cones convert energy from one form to another.= = = = Rods Are Important =

As you can see, rods are an important part of the structure of the human eye. The human eye contains 120 million rods. These rods are made up of different parts.The **nucleus** of the rod is like the **brain center**. It operates the rods. There is an **inner and outer segment** to the rods. There is also a **synaptic body** that sends nerve signals. There is also an **outer limiting membrane**. In the rods is **mitochondria**. Mitochondria is the energy part of the cell.They have a lot of mitochondria because rod and cone c ells are missing every organelle but mitochondria, nucleus, **nucleolus**, and the **cell membrane**. They don't have the other organelles since they don't need them. This The last part of the rod is the membrane shelves that contain **color pigment**. Color pigment does the primary colors of pigment are used when producing colors from reflected light. There are lots of important parts to the human rods. = = = = = = = =

= Diseases That Affect Rods =

Unfortunately, if someone has the **disease** called **retinitis pigmentosa**, their rods do not work. This disease is genetic and therefore is inherited. The most common feature of this disease is a gradual breakdown of the special cells called rods. RP (retinitis pigmentosa) is a progressive disease which means it gets worse over time. In the beginning, people with this disease struggle to adjust well to da rk and dimly lit environments because their rods are not working properly. This is called **night blindness**. The next thing that happens is that people get what’s called **tunnel vision**. This means your **periphery vision** isn’t working. In other words, you can’t see things to the side, just what’s directly in front of you. There is no cure for this disease at this time but they are researching ways to cure it.

= Conclusion = In conclusion, without rods human vision would not work. The complicated structure of the human eye as well as the rods that the eye contain must all be working in order to be able to see. Sometimes the rods fail and vision is affected. Rods are a big part of the eye.

= = = References =

Works Cited

Bianco, Carl. “How Vision Works.” How Stuff Works. N.p., 1 Apr. 2000. Web. 8 Mar. 2016. .

“Eye’s Rods and Cones.” Inner Body. Inner Body, 7 May 2015. Web. 8 Mar. 2016. .

“The Eye: Struture Foucusing.” Science Aid. N.p., 9 May 2012. Web. 8 Mar. 2016. .

“Learning about Retinitis Pigmentosa.” National Human Genome Research Institute. N.p., 27 Dec. 2013. Web. 8 Mar. 2016. .

Rods and Cones Discovery Education, 2004. Video Segment Discovery Education. Web. 17/2/2016. .