hi matrix today's lesson is on how the eye functions if you are following in your textbook we are on page 159 um in order for this lesson to be productive you really need to know um all of the structures of the eye and their basic functions so that you can follow through especially with all the terminology so you will need to know how a image is formed and the pathway that life light takes through the eye and so what we're going to look at here in this diagram is just that and all the structures that passes through so you will notice here that as light moves through the eye the first structure it's going to go through is going to be the cornea now the cornea is the further outermost layer of the eye it's a protective layer it also is where a lot of light is bent and focused so that we can see better the light then moves through the aqueous humor which is a cavity that's filled with a liquid and then the light is going to move through the pupil now the pupil is created by the iris and the iris is a circular muscle that can contract and relax depending on how much light you want to let in and if you're looking close up or far away or in bright light or in dim light now once the light ray has moved through all these structures and through the pupil it is going to encounter the lens now the lens is a structure which we use to fine tune our images it allows us to see close up but also distance and it's held in place by ciliary muscles and ligaments now once the light has moved through the lens it is going to move into what we call the vitreous humor which is again another cavity that is filled with liquid and then we want the light to move all the way to the back of the eye and we wanted to get to in particular the neural layer called the retina and the retina is where we have all of our photoreceptors photoreceptors are the rods and cones that we have in our eyes which enable us to see and give us vision now if the retina is where the image is being projected onto where we are going to receive the information then a structure called the fovea or in your textbook it's called the yellow spot is where we actually produce our highest level of focus in other words we make our sharpest vision just in this small little area over here once light has collected on the retina we need to be able to convert that light into a chemical reaction that will eventually become an impulse that can then leave the eye and go through the optic nerve to the brain in order to do that we need something called photoreceptors now i've just taken an image here where they have zoomed in on a cross-section of a piece of the retina way at the back of the eye and i'm going to quickly explain how actually this occurs so if i zoom in particularly on the structures involved what actually happens is that light makes its way first through all of these particular cell layers to the very back of the eye or the pigmented layer basically there's an epithelial layer there that has a lot of pigment in it and that's what captures um the light at the back of the eye once that has happened that then stimulates an impulse in the photoreceptors which are our rods and cones and if you remember the rods and cones are there in order to convert a light energy into a chemical energy and depending on whether or not we're looking um at color or we're looking at night or day will determine whether you're going to use more of a rod or cone vision that impulse is then going to be passed through a number of neuron cells and eventually that will then leave the eye through the optic nerve once it has left through the optic nerve it is then going to be sent to your cerebral cortex and in particular the occipital lobe which is where you interpret what you're seeing so effectively the eyes are not truly for seeing in the sense that you don't truly see with the eyes you see with your brain you interpret the images with your brain your eyes are receptors and they are receiving a stimuli which in this case is the light that stimulus is converted then into a electrochemical impulse through your neurons and then those neurons send all that information to your brain and your brain then interprets the image i'd like to point out that your the image that you do actually see is reduced in size and turned upside down but because of other mechanisms at play your brain knows that you are not upside down and so it corrects that image and the right way up how does it know to do that well that's where the ear comes into play and that will be explained in another lesson in future please yet again reach out to any of your teachers if you want clarity on this particular explanation about how the pathway of light works what might be very beneficial to you is to create a flow diagram of how light passes through each one of these structures mentioned