Rods and Cones

The human body is extremely complicated to understand and observe. People often feel that most organs work smoothly because they are not that complex in structure but on taking a closer look, they will realise that every organ, either small or big is difficult to understand. Eyes are also one of these and equally complex. Eyes are so complex to understand that people often compare them with a camera to make things more understandable. This article will also deal with some of the prominent components of human eyes.

Human Eyes

It has been found in various surveys that the eyes are the most important of all the sense organs for people, and they prefer this one organ over others because of its visual capabilities. The whole world’s existence is connected to this one small part of human cameras that continuously snap and click, presenting the human with colourful worlds. 

Eyes have many smaller components, all of which work in coordination to create a person’s vision. The front visible portion called the cornea alerts the light to pass through it and get inside the eyes. Next, there is a small opening in the eye known as the pupil, which lets the light enter through the eye and the amount of light which will enter through this art is regulated by the iris, another component. 

After this, all the light allowed to enter through the pupil passes through the lens, and the lens, along with the cornea, focuses the light on the retina, which is crucial as the retina has photoreceptors that create electric waves. Although every component of the eyes is very important, photoreceptors are the most crucial. They convert this light into waves that will ultimately be sent to the brain via the optic nerve, where the brain will create images. This whole process sounds very lengthy, but it all happens in less than a nanosecond as continuous for the whole period that the eyes are open and watching the world.

Photoreceptors

These are small cells found in the human eyes that help the eyes perceive colours and convert them into electric signals for the brain to create images and enable vision. Photoreceptors do not just work with daylight or bright light. These are equally competent to work with night vision. There are two types of photoreceptors in human eyes discussed below.

Rods: Rods are the kind of photoreceptors that help the eyes in night vision. Rods can catch things in black and white, which is the reason behind humans seeing everything in black and white at night. Everything is grey with rods because it does not have any other colour pigment, but it consists of some protein known as rhodopsin which is more like a purple pigment. Having a purple pigment does not mean that it gives a purple vision to the eyes.

Cones: Cones are the kind of photoreceptors that enable colour vision in the eyes. These receptors work in bright light and create colour visions because of the protein called photopsins which help in creating colour pigments. Even though cone photoreceptors help catch the vision of all the colour to a normal human eye, it does not consist of every pigment. Consist of only three colour pigments that are universal and are said to create all the other colours.

The three colour pigments that cones have are red, green and blue. All the three colours are stimulated alone or together depending on the light wavelengths absorbed by the eyes. If the outer light is a single colour wavelength among these three, then it will stimulate in colour, and if it is of any colour other than these, it might stimulate two or all the three as per the need.

Difference between Rods and Cones

Both the photoreceptors are extremely different and should not be confused as one. Each has its work and requirements depending on light and colour.

• Shape- The two photoreceptors present in the human eye are different in shape and work that they perform. The rod photoreceptors are in a rod-like suture, and the cone photoreceptors are in a cone shape, making it easier to retain as well
• Light- Cone photoreceptors work with bright daylight or artificial light and stimulate colours converting them into electrical signals for the brain. Rod photoreceptors do the same work, but it happens in low light or night vision with the black of colour pigments which means only grey vision
• Numbers- Human eyes want to see everything in colour. Still, the number of colour photoreceptors is around 6 million, which is extremely less in number when compared to rod photoreceptors, which are around 120 million in numbers
• Colours- Cone photoreceptors contain red, blue and green colour pigments, which are stimulated together or alone to create colourful images. On the other hand, rod photoreceptors lack these colours and work in black and white creating grey images
• Location- Cones are located in the retina’s centre, and rods are located in the corner of the retina

Conclusion

The bottom line is that both photoreceptors have their work and specific way of creating images. Both of them work with different light, colours and wavelengths. None is more important than the other. If a person loses cones, they’ll become colour blind, and if they lose rods, it will lead to loss of night vision. Hence, one should take extreme care of these two pairs of delicate organs present in the human body.