Download Enhancing the senses – worksheet Eye Anatomy Zonules The fiber

Enhancing the senses – worksheet
Eye Anatomy
Zonules
The fiber-like processes extending
from the ciliary body to the capsule
of the lens of the eye. The zonules
are responsible for holding the lens
of the eye in its normal position.
Sclera
The white outer wall of the eye.
Cornea
The front clear "window" of the eye
(where a contact lens rests). The
cornea is responsible for focusing
light rays to the back of the eye.
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Retina
The layer of tissue lining the inside of the back of the eye. The retina contains
millions of photoreceptor cells which convert light into images.
Macula
The center of the retina which is responsible for about the central 15 degrees of
vision. The macula is approximately 5.5mm (less than 1/4 inch) in diameter.
Optic Nerve
The bundled collection of the retinal nerve fiber layer which transmits visual
information from the eye to the brain.
Iris
The colored structure which rests behind the cornea and in front of the natural
lens. The opening in the center of the iris is the pupil. The iris acts like a camera
shutter and controls the amount of light that enters the eye.
Lens
Normally clear, the lens sits behind the iris and in front of the vitreous humor.
The lens focuses light rays on the back of the eye.
Ciliary Body
Located just behind the iris, the ciliary body is instrumental in controlling
focusing of the eye and the production of aqueous fluid.
Choroid
A vascular layer situated between the retina and the sclera of the eye.
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Your ears are not just for hearing — they are also important for controlling
position sense and balance. Each ear is divided into 3 sections: the outer;
middle; and inner ear. The middle and inner parts of the ear are located in
hollow spaces on either side of the head within the temporal bones of the skull.
The outer ear
The external part of your ear consists of the pinna and ear lobe. The pinna is
the shell-like part of your external ear, and is made of cartilage and skin. It
directs sound waves from the outside into your external auditory canal (ear
canal), which in turn channels sound waves to the tympanic membrane (better
known as the ear drum). The tympanic membrane is a thin, semi-transparent
membrane that connects the outer and middle ear.
The middle ear
The middle ear is an air-filled space that contains 3 tiny bones (also known as
ossicles), called the malleus, incus and stapes (stirrup). Sound waves that
reach the tympanic membrane cause it to vibrate. This vibration is then
transmitted to the ossicles, which amplify the sound and pass on the vibration to
the oval window (a thin membrane between the middle and inner ear).
The Eustachian tube is a narrow tube that connects your middle ear to the back
of your nose and throat. When you swallow, your Eustachian tube opens up to
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allow air into the middle ear, so that the air pressure on either side of the
tympanic membrane is the same. In situations when there is a sudden change in
air pressure (e.g. during take off and landing when travelling on a plane), the
pressure in the middle ear is not the same as the outside air pressure. This can
make your ear drum bulge or retract and less able to transmit vibrations, causing
temporary hearing problems. By swallowing or ‘popping’ your ears, you can
equalise the pressure.
The inner ear
The inner ear (also called the labyrinth) contains 2 main structures — the
cochlea, which is involved in hearing, and the vestibular system (consisting of
the semicircular canals, saccule and utricle), which is responsible for
maintaining balance.
The cochlea is filled with fluid and contains the organ of Corti — a structure that
contains thousands of specialised sensory hair cells with projections called cilia.
The vibrations transmitted from the middle ear cause tiny waves to form in the
inner ear fluid, which make the cilia vibrate. The hair cells then convert these
vibrations into nerve impulses, or signals, which are sent via the auditory nerve
to the brain, where they are interpreted as sound.
The round window (fenestra cochlea) is a membrane that connects the
cochlea with the middle ear. It helps dampen the vibrations in the cochlea.
The semicircular canals also contain fluid and hair cells, but these hair cells are
responsible for detecting movement rather than sound. When you move your
head, the fluid within the semicircular canals (which sit at right angles to each
other) also moves. This fluid motion is detected by the hair cells, which then
send nerve impulses about the position of your head and body to the brain to
allow you to maintain your balance.
The utricle and saccule work in a similar way to the semicircular canals, allowing
you to sense your body’s position relative to gravity and make postural
adjustments as required.
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SPECIAL RECEPTOR CELLS FOR EACH OF THE SENSES
Vision: rod + cone
Hearing
Smell
Taste
Touch: free nerve-ending, Meissner Corpuscule
Rod and cone cells in the eye respond to electromagnetic
radiation—light.
The ear’s receptor neurons are topped by
hair bundles that move in response to vibrations—
sound.
Olfactory neurons at the back of the nose
respond—and bind—to odorant chemicals .
Taste receptor cells on the tongue and back
of the mouth respond—and bind—to chemical
substances.
Meissner corpuscles are specialized for
rapid response to touch, while free nerve endings
bring sensations of pain
http://library.thinkquest.org/3750/smell/smell.html
http://yucky.discovery.com/flash/body/pg000150.html
http://library.thinkquest.org/3750/taste/taste.html
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