Structure and function of the human eye.pdf
- 1. STRUCTURE & function O F T H E H U M A N E Y E
- 3. Iris - It is the circular, colored area of the eye that surrounds the pupil. FUNCTIONS: It controls the amount of light entering the eye by regulating pupil dilation. The parts of the eye Cornea - It is the transparent covering of the front of the eye. FUNCTIONS: The cornea serves as a protective covering for the front of the eye and also helps focus light on the retina at the back of the eye.
- 4. Retina - The sensory membrane that lines the inner surface of the back of the eyeball containing photoreceptor cells. FUNCTIONS: Photoreceptor cells take light focused by the cornea and lens and convert it into chemical and nervous signals which are transported to visual centers in the brain by way of the optic nerve Sclera - The outer covering of the eyeball consists of a relatively tough, white layer is called the sclera (or white of the eye). FUNCTIONS: It surrounds the rest of the eye. It protects the eye and maintains its shape.
- 5. Lens - The transparent structure inside the eye that focuses light rays onto the retina. FUNCTIONS: Through the actions of the ciliary muscles, the lens becomes thicker to focus on nearby objects and thinner to focus on distant objects. Pupil - The hole or opening in the middle of the iris. FUNCTIONS: It allows light to enter into the eye.
- 6. Vitreous humor - It is a water-like fluid which fills the aqueous chamber between lens and the retina. FUNCTIONS: It provides nutrition for the eye and maintains the shape of the eye lens. Aqueous humour - It is a water like fluid which fills the aqueous chamber between lens and the cornea. FUNCTIONS: It provides nutrition for the eye and maintains the shape of the eye lens.
- 7. Ciliary muscles - Rounded, smooth muscles that hold the zonules in place and bring about their contraction or relaxation to alter the shape of the lens. FUNCTIONS: Regulates the process through which the lens changes its shape in order to focus the objects at varying distances. Optic nerves - The connection between the eyes and the brain FUNCTIONS: Sends the brain signals from the eye describing what they detect or see.
- 8. Cones - The receptors for photopic (day light) vision. FUNCTIONS: They operate at high levels of illumination, and lead to chromatic (coloured) vision. Rods - The receptors for scotopic vision (night vision). . FUNCTIONS: They operate at low intensities of light, and lead to achromatic (colourless) vision.
- 9. Light enters the eye through the cornea. Because of the shape of the cornea, it exits pre-focused. From the cornea, light passes through the aqueous humor and through the pupil. From here, light strikes the lens. The lens further focuses light, depending on whether you’re looking at a near or distant object. Light exits the lens and passes through the vitreous humor. Ideally, the vitreous humor is clear and allows light to travel unimpeded to the retina. How does the eye work?
- 10. Light reaches the retina, activating rods and cones to generate electrical impulses that code for an inverted image. Signals from the rods and cones travel through the optic nerve to the brain. The neural impulse is transmitted to the visual cortex through the optic nerve where the image is re-inverted and processed. The brain compares left/right vision to add depth and make the image three-dimensional. It also flips the image so it appears right- side up.
- 11. Light Adaptation: Light adaptation refers to the process of adjusting to bright light after exposure to dim light. This process takes nearly a minute or two. Dark adaptation: Dark adaptation refers to the process of adjusting to a dimly illuminated environment after exposure to bright light. This may take half an hour or even longer depending on the previous level of exposure of the eye to light. Adaptation
- 12. Light and dark adaptation takes place due to photochemical processes. Light adaptation takes place when the molecules of rhodopsin or visual purple in the rods of the eye get bleached or broken down, as a result of the action of light. Dark adaptation takes place when the light is removed allowing for restorative processes that regenerate the pigment in the rods with the help of vitamin A. Photochemical basis of light and dark adaptation
- 13. Thank you