Animation

 http://m.youtube.com/watch?v=yUWb84ER4O0

http://m.youtube.com/watch?feature=related&v=DWue7byOsjc#/watch?feature=related&v=DWue7byOsjc

http://m.youtube.com/watch?feature=related&v=1Y-HghqvGtg#/watch?feature=related&v=1Y-HghqvGtg

Physiology of hearing

• Sound is vibration moving through the air. When we hear, the wave passes through four mediums along the auditory system. The four mediums are: Outer, middle, inner, and neural (the brain).
• Outer Ear- Sound is helped pass through by the outer ear and funnels the waves into the ear canal.'
• Middle Ear- Air movement hits the tympanic membrane, (ear drum) and it moves. Then the wave is sent through air that is a solid medium inside the middle ear.
• The Oscular chain is connected to the ear drum by malleus. It is made up of three bones and helps transport sound to the next medium.
• Inner Ear - The oscular chain transfers the energy from a solid medium to a fluid medium by the stapes. Stapes are attatched to the oval window. The motion through the inner ear stimulates frequency specific areas of the Organ of Corti and then stimulates the nerve endings.
• Neural - Receiving the nerve impulses the fluid turns to a neural medium. The brain then reads the neural impulse and in turn interprets it, creates a thought or picture, and then it is recognized by the brain.

The process of hearing begins with the occurrence of a sound. Sound is initiated when an event moves and causes a motion or vibration in air. When this air movement stimulates the ear, a sound is heard.

In the human ear, a sound wave is transmitted through four separate mediums along the auditory system before a sound is perceived: in the outer ear—air, in the middle ear— mechanical, in the inner ear liquid and to the brain—neural.

Sound Transmission through the Outer Ear
Air transmitted sound waves are directed toward the delicate hearing mechanisms with the help of the outer ear, first by the pinna, which gently funnels sound waves into the ear canal, then by the ear canal.

Sound Transmission through the Middle Ear
When air movement strikes the tympanic membrane, the tympanic membrane or eardrum moves. At this point, the energy generated through a sound wave is transferred from a medium of air to that which is solid in the middle ear. The ossicular chain of the middle ear connects to the eardrum via the malleus, so that any motion of the eardrum sets the three little bones of the ossicular chain into motion.

Sound Transmission through the Inner Ear
The ossicular chain transfers energy from a solid medium to the fluid medium of the inner ear via the stapes. The stapes is attached to the oval window. Movement of the oval window creates motion in the cochlear fluid and along the Basilar membrane. Motion along the basilar membrane excites frequency specific areas of the Organ of Corti, which in turn stimulates a series of nerve endings.

Sound Transmission to the Brain
With the initiation of the nerve impulses, another change in medium occurs: from fluid to neural. Nerve impulses are relayed through the VIII C.N., through various nuclei along the auditory pathway to areas to the brain. It is the brain that interprets the neural impulses and creates a thought, picture, or other recognized symbol.

 

 

Ear

 

 

External, middle, internal ear: one of two organs of hearing on the sides of the head, comprised of internal and external parts.
External ear: visible part of the ear.
Auricle: outer part of the external ear.
External auditory meatus: canal of the temporal bone that carries sounds to the eardrum.
Eardrum: membrane of the external ear that transmits air vibrations to the middle ear.
Internal ear: deepest part of the ear.
Semi-circular canans: crescent-shaped tubes.
External: semicircular tube closest to the external ear.
Posterior: middle semicircular tube.
Anterior: semicircular tube deepest in the ear.
Vestibuli: cavity of the internal ear.
Cochlea: part of the internal ear that converts sound vibrations to nerve impulses.
Auridory nerve: nerve related to hearing.
Eustachian tube: canal that allows equalization of air pressure on both sides of the eardrum.
Middle ear: part of the ear between the internal and external ears.
Stapes (stirrup): ossicle of the middle ear connected to the incus.
Incus (anvil): middle ossicle of the middle ear.
Malleus (hammer): first ossicle of the middle ear.
External acoustic meatus: canal of the temporal bone that carries sounds to the eardrum.

 

Your ears are amazing. The inner ear can detect your position of the body in relation to the original pull of gravity on the body and can tell you when it is different and when it comes back to normal. If you do a dive off of a diving board, you will unknowingly realize when you are upside right or inverted to any degree other than upright. The reason is there are patches of hair cells which are attached to thousands of tiny spheres of calcium carbonate (CaCO3) and these are pulled downward by gravity and the brain gets notified of any changes such as a nod of the head or any other disorientation and your body reacts to this change therefore equilibrium can be maintained.

http://wiki.answers.com/Q/How_do_your_ears_help_you_maintain_your_balance#page4

Astigmatism

• Astigmatism is an eye condition that causes blurred vision occurred either by irregular shape of the cornea, the clear front cover of your eye, or the curvature of the lens inside of your eye.
• Irregular shapeed cornea or lens causes the light to be prevented from focusing properly on the retina.

 

Astigmatism is a vision condition that causes blurred vision due either to the irregular shape of the cornea, the clear front cover of the eye, or sometimes the curvature of the lens inside the eye. An irregular shaped cornea or lens prevents light from focusing properly on the retina, the light sensitive surface at the back of the eye. As a result, vision becomes blurred at any distance.
-http://www.aoa.org/Astigmatism.xml

Farsighted Vision (Hyperopia)

• farsighted vision also known as Hyperopia, is an eye condition where a person has difficulty seeing objects closer to the eye, but the ability of seeing far away is good.
• Its an inherited vision, thats caused by an abnormally short eye.

 

Hyperopia, also called farsightedness, is a condition in which a person has difficulty seeing objects that are located close to the eye, although vision of distant objects (that is, far vision) is good.
In most cases, farsightedness is an inherited condition that is caused by an abnormally short eye, as measured from front to back. This situation reduces the distance between the cornea (the clear film that covers the front of the eye) and the retina (the light-sensitive layer at the back of the eye). As a result, images tend to focus behind the retina, rather than on the retina itself. Sometimes, the eye is able to partially or totally compensate for this focusing problem through a process called accommodation. In accommodation, tiny ciliary muscles within the eye contract, altering the shape of the lens and bringing the viewed object into focus.
http://www.visionforegolfing.com/golfing_eyeglasses/vision_problems/hyperopia.asp

Nearsighted Vision (Myopia)

• Nearsighted vision ,also known as Myopia, is a eye problem that causes objects in a distance to appear blurry.
• Hard to focus on objects that are far away.
• occurs when eyeeball is slightly longer than normal or the cornea is steeper than average.

Nearsightedness, or myopia, is an eye problem that causes objects at a distance to be blurry. A nearsighted person can clearly see objects that are close to them, but has a hard time focusing on objects that are far away.
Causes:
Nearsightedness occurs when the eyeball is slightly longer than normal, or when the cornea is steeper than average. These conditions cause light to focus in front of the retina instead of directly on its surface. In most cases, nearsightedness is inherited. However, there is some evidence that suggest that intense close-up activities, such as reading for prolonged periods of time at close range or playing video games for many hours, in early adulthood can induce nearsightedness.
http://vision.about.com/od/commonvisionproblems/a/nearsighted.htm

 

 

Rods and Cones

• Rods also known as scoptic vision, is the vision at low light levels
• Dont mediate color vision, and only have a low spatial acuity.
• Cones also known as photopic vision, are more active at higher levels.
• Cones are capable of color vision and have high spatial acuity.

 

 

Rods are responsible for vision at low light levels (scotopic vision). They do not mediate color vision, and have a low spatial acuity.

Cones are active at higher light levels (photopic vision), are capable of color vision and are responsible for high spatial acuity. The central fovea is populated exclusively by cones. There are 3 types of cones which we will refer to as the short-wavelength sensitive cones, the middle-wavelength sensitive cones and the long-wavelength sensitive cones or S-cone, M-cones, and L-cones for short.
http://www.cis.rit.edu/people/faculty/montag/vandplite/pages/chap_9/ch9p1.html