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human eye

Transcript: The cones are not as sensitive to light as the rods. However, cones are most sensitive to one of three different colors (green, red or blue). Signals from the cones are sent to the brain which then translates these messages into the perception of color. Cones, however, work only in bright light. That's why you cannot see color very well in dark places. So, the cones are used for color vision and are better suited for detecting fine details. There are about 6 million cones in the human retina. The rods are sensitive to light and dark changes, shape and movement and contain only one type of light-sensitive pigment. Rods are not good for color vision. Rods are more numerous than cones in the retina. There are about 120 million rods in the human retina. Some people cannot tell some colors from others these people are "color blind." Someone who is color blind does not have a particular type of cone in the retina or one type of cone may be weak. Most people wear glasses because they are either farsighted or nearsighted. Farsighted means that you can see images farther away but not up close. Nearsighted means the opposite: you can see close up, but images farther away are blurry, unfocused. This happens because what you are seeing—the images—are not projecting on your retina in the correct spot. Nearsighted people have images focusing in front of the retina. Farsighted people have images focusing behind it. There are other conditions that prompt the need for corrective eyewear and contacts, but these are the most common. Here are some of the warning signs that you might need vision correction: Refraction is the part of an eye or vision exam in which the eye doctor determines your need for glasses. He or she refracts your vision by using a phoropter, a device that contains hundreds of combinations of lenses, to determine any possible refractive error such as nearsightedness, farsightedness, astigmatism, or presbyopia. Rods and Cones Refraction The retina is the back part of the eye that contains the cells that respond to light. These cells are called photoreceptors. There are 2 types of photoreceptors in the retina: rods and cones. Glasses and contacts are uniquely designed to meet the needs of your eyes. Your eye doctor works up a ratio or a fraction that tells those making the glasses what kind of vision you have and what kind of lenses you need. They also will use measurements to help images focus on the correct spot on your retina. Your lenses will bend and focus light at precise angles in order for those images to target the center of your retina. Both glasses and contacts correct vision in the same way. Glasses are worn over your eyes and are anchored by your nose and ears, while contacts are fitted to the dimensions of your eye itself. Those who alternate wearing eyeglasses and contacts usually feel that contacts give better depth perception and lets them see better side to side. Color Blind Your eyes can get infections from bacteria, fungi or viruses. Eye infections can occur in different parts of the eye and can affect just one eye or both. Two common eye infections are Conjunctivitis - also known as pinkeye. Conjunctivitis is often due to an infection. Children frequently get it, and it is very contagious. Stye - a bump on the eyelid that happens when bacteria from your skin get into the hair follicle of an eyelash. Symptoms of eye infections may include redness, itching, swelling, discharge, pain, or problems with vision. Treatment depends on the cause of the infection and may include compresses, eye drops, creams or antibiotics. By: Erica Castrejon & Eugenia Astudillo Infections Nearsighted/ Farsided Laser Eye Surgery Glasses/Contacts How It Works The eyeball and its lens focus light from an image onto the retina. The amount of light entering the eye is controlled by the pupil, which opens and closes. The light sensitive cells on the retina detect the electrical impulses and they travel to the brain. Although the image is inverted when received, the brain automatically produces it upright. The Human Eye Credits

Human Eye

Transcript: When light reaches either the rods or the cones of the retina, it's converted into an electric signal that is sent to the brain through the optic nerve. The brain then recieves the electrical signals as the images we see. When the muscles relax, they pull on and flatten the lens, allowing the eye to see objects that are far away. To see closer objects clearly, the ciliary muscle must contract in order to thicken the lens. The cornea, a transparent structure in the very front of the eye, helps focus incoming light. Behind the cornea, the iris has an adjustable circular opening called the pupil, which can expand or contract depending on the amount of light entering the eye. Pupil- An opening in the center of the iris that controls how much light enters the eye. The iris functions like the iris of a camera, which opens and closes, to control the amount of light that enters through the pupil. The Human Eye Retina-The membrane that lines the back of the eye, containing photoreceptor cells. The photoreceptor nerve cells react to the presence and intensity of light by sending impulses to the brain through the optic nerve. In the brain, the nerve impulses that are received from the photoreceptor cells, are assimilated into images. The first thing light touches when entering the eye is a thin veil of tears that coats the front of the eye. Behind the moisture is the front window of the eye, called the cornea. This clear covering helps to focus the light. Lens- Immediately behind the iris, it performs delicate focusing of light rays to the retina. People under 40, the lens is soft and pliable, allowing for fine focusing from a variety of distances. People over 40, the lens begins to become less pliable, making focusing upon objects near to the eye more difficult, known as presbyopia. Cornea- Is the primary focusing element of the eye. The outer layer is the epithelium, which protects the eye and is made of transparent cells that have the ability to regenerate quickly. The inner layer is also made of transparent tissue, which allows light to pass. Anatomy How The Eye Works

Human Eye

Transcript: Sites and Sources The field of view of a human eye is around 95 degrees away from the nose, 75 degrees downward, 60 degrees toward the nose, and 60 degrees upward. Humans almost have a 180 degree forward-facing view. Structure The eye has three coats, the outermost layer, the middle layer, and the innermost layer. The outermost layer is known as fibrous tunic, the middle layer is known as vascular tunic or uvea, and the innermost layer is known as retina. - Eating right - Maintain a healthy weight - Wear protective eyewear - Quit smoking or never start - Know your family's health history Size The human eye is not a perfect circle, it is more like a 2 piece unit. A smaller unit called the cornea is linked to the larger unit called the scerla. They are attached by a ring called the limbus. The radius of the corneal segment is usually around 8 millimeters. The color of your eye is called the iris. The pupil is the black part of your eyeball. How to keep your eyes healthy The dimensions differ between age, but only by one or two millimeters. At birth, the size of your eye is around 16-17 millimeters. The adult eye is about 23-24 millimeters. By the age of 13 the eye reaches its full size. Cameron Critch Responsibility Components - Prevent human from harm - Retina is responsible for peripheral vision - Sends messages to brain of your surroundings. - Allows you to see clearly Human Eye Vision

Human Eye

Transcript: A blind person gets around by walking stick specifically for blind people. Blind people also walk with a service dog. A service dog is a dog that helps people with problems or helps a blind person walk. Also a blind person can get around by their hearing. Finally, a blind person gets around by a person such as a family member. These are ways blind people get around. by pre Intro Do Blind People See Dreams? How a Blind Person Gets Around What causes people to go blind is if the optic nerve becomes damaged. It would interrupt the flow of visuals to your brain. Light enters through the cornea and lens helping your brain to focus on something or someone.If your cornea or lens get messed up,You can also go blind from an eye disease called Glacuma. Another cause is Macular degeneration that is a condition affecting the rectina. Another example is sports injury's messing up your eyes. Human Eye Conclusion Causes of Blindness Do blind people see in their dreams? The answer is yes and no. Blind people only see auditory dreams meaning they only see what they hear so they imagine their dreams. If a person at one point could see, and than went blind they could memorize someones voice and remember the persons face, However it may still be blurry. Another way blind people see dreams is they imagine what a dream would look like. This is how a blind person sees dreams. In conclusion, its pretty fascinating that a blind person can only see what they hear in their dreams. When blind people walk they either use a walking stick, their hearing, or a service dog. It is important to be careful because anything that could injure you in your eye could cause you to go blind. Imagine not being able to see for one week, Now, imagine not being able to see for the rest of your life.90% of people in the world suffer from blindness.What causes blindness?How would a blind person get around?Do people see dreams when they're blind?Well I'm going to answer all those questions. add logo here

Human Eye

Transcript: The human eye refracts light emitted off objects and onto the retina to bring the objects being viewed into focus Light rays pass through the eye’s clear front cover called the cornea Then light passes through the eyes pupil,The pupil is surrounded by a sphincter call the iris; the eye’s colored ring. Then light passes through the eye’s crystalline lens, which constricts to help light rays come to focus at one focal point. After that light rays travel to and come to rest on the retina resulting in clear vision Once light rays come to rest on the retina a signal is carried done the optic nerve to the brain Then the brain receives the signals and interprets them into a picture(s). The brain then tells the eyes what it sees by forming the picture The Visible Light Spectrum Hearing Pascal's Law pressure exerted on a confined incompressible fluid is equally distributed in all directions throughout various point of the fluid The Outer ear • MRI is a technique used for diagnosing and treating medical conditions. • Powerful magnetic fields and radio frequency pulses are used to make pictures of organs, tissues, bones, and other internal body structures. • An MRI machine can produce thorough images of where water molecules are in the patient, where fat molecules are and where the patients blood is flowing. The ear consists of 3 parts: the outer ear or external ear, the middle ear and the inner ear. The function of the outer ear is to collect and send sound to the middle ear. The ear drum vibrates when sound travels along the ear canal. Sound in the outer ear is in the form of pressure wave. Vasconstriction -High BP Hypertension Physics in the Human Body is the pressure of the blood in the circulatory system Vasodilation- Low BP X-Rays Importance • Gamma rays are an electromagnetic radiation with the shortest wavelength and the highest energy. • The easiest way to obtain very high energy photons for gamma rays is through the decay of radioactive isotopes, which are commonly used for radiation therapy. • This technique can be used for the treatment of cancer cells and can detect brain and heart abnormalities. • Photographic film is used to detect gamma rays as they pass through the body. Magnetic Resonance Imaging (MRI) Power medical conditions Does mechanical work, ; heart exerts a force on the blood giving it kinetic energy Movement of blood is effected by many factors pressure, volume, temperature etc. Gamma Rays Human Eye Color comes from light made up of different wavelengths or frequencies. Different frequencies make different colors The range of colors that are visible to the human eye can be found on the electromagnetic spectrum within the visible spectrum range when light of at particular wavelength strikes the retina of our eye; we notice that specific color sensation The Middle and Inner ear Blood Pressure The heart functions by pumping blood both to the lungs and to the systems of the body. Hydraulics The human ear converts sound energy into mechanical energy and then into electrical nerve signals, which are then transmitted to the brain. The ear allows us to hear the pitch of sounds by detecting the wave's frequencies. It allows us to hear the loudness of sounds by detecting the wave's amplitude and the timbre of sounds by detecting the many frequencies that create a sound wave. How the Human Eye Works The heart contains 4 chambers: the right atrium, left atrium, right ventricle, and left ventricle. The three small bones of the middle ear called the hammer, anvil and stirrup transmit the vibration from the eardrum to the cochlea, which is the auditory portion of the inner ear. The middle ear is connected to the mouth by the Eustachian tube. The cochlea is filled with a water-like fluid and is lined with many hair cells. Each hair cell is sensitive to a particular frequency of vibration and it releases an electrical current. The brain processes the electrical current and interprets it as sound. • X-rays were discovered in 1895 by a German physicist named Wilhelm Conrad Roentgen. • X-rays are a form of electromagnetic radiation, which carries a high frequency of X-ray photons. • A photon is a particle of electromagnetic radiation. • 2 ways to create X-rays are Bremsstrahlung and X-ray fluorescence. Bibliography THE HEART Medical Imaging Hearing and Ear Heart and Circulatory System

Human eye

Transcript: Human Eye The human eye is an organ which reacts to light for several purposes. As a conscious sense organ, the mammalian eye allows vision. Rod and cone cells in the retina allow conscious light perception and vision including color differentiation and the perception of depth. The human eye can distinguish about 10 million colors. In common with the eyes of other mammals, the human eye's non-image-forming photosensitive ganglion cells in the retina receive the light signals which affect adjustment of the size of the pupil, regulation and suppression of the hormone melatonin and entrainment of the body clock. General Properties The eye is not shaped like a perfect sphere, rather it is a fused two-piece unit. The smaller frontal unit, more curved, called the cornea is linked to the larger unit called the sclera. The corneal segment is typically about 8 mm (0.3 in) in radius. The sclerotic chamber constitutes the remaining five-sixths; its radius is typically about 12 mm. The cornea and sclera are connected by a ring called the limbus. The iris – the color of the eye – and its black center, the pupil, are seen instead of the cornea due to the cornea's transparency. To see inside the eye, an ophthalmoscope is needed, since light is not reflected out. The fundus (area opposite the pupil) shows the characteristic pale optic disk (papilla), where vessels entering the eye pass across and optic nerve fibers depart the globe. Dimensions The dimensions differ among adults by only one or two millimeters. The vertical measure, generally less than the horizontal distance, is about 24 mm among adults, at birth about 16–17 millimeters (about 0.65 inch). The eyeball grows rapidly, increasing to 22.5–23 mm (approx. 0.89 in) by three years of age. By age 13, the eye attains its full size. The typical adult eye has an anterior to posterior diameter of 24 millimeters, a volume of six cubic millimeters (0.4 cu. in.),[3] and a weight of 7.5 grams (0.25 oz.). Components The eye is made up of three coats, enclosing three transparent structures. The outermost layer is composed of the cornea and sclera. The middle layer consists of the choroid, ciliary body, and iris. The innermost is the retina, which gets its circulation from the vessels of the choroid as well as the retinal vessels, which can be seen in an ophthalmoscope. Within these coats are the aqueous humor, the vitreous body, and the flexible lens. The aqueous humor is a clear fluid that is contained in two areas: the anterior chamber between the cornea and the iris, and the posterior chamber between the iris and the lens. The lens is suspended to the ciliary body by the suspensory ligament (Zonule of Zinn), made up of fine transparent fibers. The vitreous body is a clear jelly that is much larger than the aqueous humor, present behind lens and the rest, and is bordered by the sclera, zonule, and lens. They are connected via the pupil. Dynamic range The retina has a static contrast ratio of around 100:1 (about 6.5 f-stops). As soon as the eye moves (saccades) it re-adjusts its exposure both chemically and geometrically by adjusting the iris which regulates the size of the pupil. Initial dark adaptation takes place in approximately four seconds of profound, uninterrupted darkness; full adaptation through adjustments in retinal chemistry (the Purkinje effect) is mostly complete in thirty minutes. Hence, a dynamic contrast ratio of about 1,000,000:1 (about 20 f-stops) is possible. The process is nonlinear and multifaceted, so an interruption by light merely starts the adaptation process over again. Full adaptation is dependent on good blood flow; thus dark adaptation may be hampered by poor circulation, and vasoconstrictors like tobacco.[citation needed] The eye includes a lens not dissimilar to lenses found in optical instruments such as cameras and the same principles can be applied. The pupil of the human eye is its aperture; the iris is the diaphragm that serves as the aperture stop. Refraction in the cornea causes the effective aperture (the entrance pupil) to differ slightly from the physical pupil diameter. The entrance pupil is typically about 4 mm in diameter, although it can range from 2 mm (f/8.3) in a brightly lit place to 8 mm (f/2.1) in the dark. The latter value decreases slowly with age; older people's eyes sometimes dilate to not more than 5-6mm. Field of view The approximate field of view of an individual human eye is 95° away from the nose, 75° downward, 60° toward the nose, and 60° upward, allowing humans to have an almost 180-degree forward-facing horizontal field of view.[citation needed] About 12–15° temporal and 1.5° below the horizontal is the optic nerve or blind spot which is roughly 7.5° high and 5.5° wide. Eye irritation Eye irritation has been defined as “the magnitude of any stinging, scratching, burning, or other irritating sensation from the eye”. It is a common problem experienced by people of all ages. Related eye symptoms and signs of

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