Transcript Eye presentation

Eye presentation
Uly, Elizabeth, Zulema
Period 4
General Function
❏ light detection
❏ focus
❏ balance
❏ depth perception
❏ works with brain to
provide us with
vision
Parts of Eye and Function
Outer Tunic (Fibrous)
●
Cornea
o
Clear front window of the eye
o
Transmits and focuses (sharpness or clarity) light
into the eye
●
Sclera
o
White outer coat of eye surrounding iris
o
Acts as a tough protection from injury
o
provides attachment for the extraocular muscles
that move the eye
●
Conjunctiva
o
Thin, transparent tissue covering the outer surface
of eye
o
Begins in outer edge of cornea, covering the visible
part of sclera, and lining the inside of the eyelids
o
Nourished by tiny blood vessels
Continue...
Middle Tunic (Vascular)
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Choroid
o Lies btw retina and sclera
o Composed of blood vessels that nourish the back
of the eye
Ciliary Body
o Releases transparent liquid (aqueous humor)
within the eye
o accommodation

ciliary muscle changes shape of lens when
eyes focus on something
Iris
o Colored part of eye
o Regulates the amount of light entering the eye
o Closes when there’s bright light to let in less
light, and opens when there’s low light to let in
more light
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Pupil
○ ark center opening in the middle of the iris
○ Changes size to adjust for amounts of light
available (smaller for bright Light and larger for
low)
Lens
○ Transparent and can be replaced
○ Focuses light rays onto the retina
Suspensory Ligaments
○ Adjust the shape of lends
■ more or less curved
■ increase or decrease the refraction of
light
○ Connect the ciliary muscles to lens to hold them
in place
Continued...
Inner Tunic (Nervous)
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Macula
o Area in retina containing special lightsensitive cells
o These cells allow us to see fine details clearly
in the center of our visual field
Optic Nerve
o Bundle of more than 1 million nerve fibers
carrying visual messages from retina to brain
o Transfer visual info from retina to visual
centers of the brain via electrical impulses
Retina
o Nerve layer lining the back of the eye
o Senses light and creates electrical impulses
that are sent through the optic nerve to brain
Fovea
o Center of medulla
o Provides sharp vision
●
Vitreous Humor
○ The clear gel that fills the space between
the lens and the retina of the eyeball
○ Often referred to as the vitreous body or
simply “the vitreous”
Neurons Involved
●
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Sensory
o Detect info through receptors and travels
through the nerves to the brain
Bipolar
o Transfer signal from receptor cells to the
ganglion cells
o Signals carry visual info to the brain
through optic nerve
Ganglion
o Located in the inner surface of the retina
o Transmits image and non-image visual info
to many regions
o Consists of axon and dendrite structures
that send and receive nerve impulses
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Amacrine
○ Integrate for ganglion cells the signal
coming from bipolar neurons
○ Interneurons
○ 22 types of amacrine cells
○ Supplement the action of horizontal cells
Horizontal
○
Integrate and regulate the input from
receptor cells
○ Allows eyes to adjust to dim and bright
lights
Photoreceptors
○
Responds to the stimuli after receiving
signals
○ Convert light into signal
○
2 types: rod and cones
Visual Receptors
● Visual processing begins at
retina.
● Light enters eye and passes
through
1. Cornea
2. Anterior Chamber
3. Lens
4. Vitreous
5. Photoreceptor cells:
● Cones
● Rods
Rods
● Located mainly near your peripheral sides of the retina
● Nerve fiber coverage
●
contains light sensitive pigment called rhodopsin.
●
provides vision in dim light and also provides colorless vision.
● Produces response to single photon.
● 100-120 million rods in a human retina
Cones
● Detect colors
● 4-6 million cones
● Nonconvergent
● Densely packed with fovea centralis
● Attached to pigmented epithelium
● Contains iodopsins
3 types1. Erythrolabe
2. Chlorolabe
3. Cyanolabe
Chambers
● Anterior Chamber
-
Small area filled with aqueous
● Posterior Chamber
-
Behind peripheral part of iris
Anterior to lens
Contains aqueous humor
● Vitreous Chamber
-
Large space between lens and retina
Filled with vitreous humor
Fluids
● Aqueous Humor
-Fluid nourishes cornea and lens
- Gives the eye its shape
-Produced by ciliary body
● Vitreous Humor
-
80% eye volume
98% water
Contains collagen, salt and
sugar
Large molecules of hyaluronic
acid
Accessory Organs
●
-
Ocular Muscles
Lateral rectus
Medial rectus
Superior rectus
Superior oblique
Inferior oblique
● Eyebrows
- Catch sweat or debris coming off forehead into the eye
● Eyelids
-Hairs growing at the edge of the eyelids are very sensitive, tactil
receptors.
●
Fasciae
- Envelopes bulb of eye from optic nerve to cilia region.
●
Conjunctiva - inner layer eyelids laying on cornea.
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Lacrimal glands - Secretes tears, water, enzymes,
salts, oxygen, and nutrients.
Tarsal glands- Next to eyelashes, secretes substance to
keep eyelids from sticking together.
●
How we interpret sight
Refraction
Once light enters the eye it must make it past:
● the cornea,
● aqueous humor,
● lens,
● vitreous humor, and several layers of the retina before reaching the eye.
An image of what is seen focuses upon the retina then the light rays must bend
to be focused on, this is called a refraction. Refraction occurs when light
waves pass at an oblique angle from a medium of one optical density into a
medium of a different optical density.
Refraction pictures
Convergent vs Divergent waves
● Lens with a convex surface
causes light waves to
converge. (inward)
● Lens with a concave
surface causes light waves
to diverge. (outward)
● Converging means to come
together from different
points to eventually meet
at one point.
● Diverging means to
separate or to split apart
from the main direction
and to go to a different
direction
Concave and convex reflections
How an image is flipped
1. Normal shaped eye
2. Light waves are focused sharply on the
retina.
3. Those waves formed on the retina make
an image appear upside down and
reversed from left to right.
4. When the visual cortex of the cerebrum
interprets such an image, it will then
correct it, and objects are seen in their real
position.
Example of a flipped image
Dark vs light vision
Rhodopsin
● light sensitive pigment in rods photoreceptors
● they are embedded in membranous discs that are stacked within the receptor cells.
Iodopsins
● light sensitive pigment in cones
Dark vs light cont
In light: rhodopsin molecules break down into molecules of a colorless protein called
opsin and a yellowish organic molecule called retinal.
In darkness: the sodium channels in receptor cell membranes are opened by
nucleotides, cyclic guanosine monophosphate (cGMP), when the molecules absorb
sunlight they change shape and release opsin.
Stereoscopic vision
● Simultaneously perceives distance, depth, height, and width of objects.
● 3D Vision
● Pupils 6-7 cm apart make this possible.
● This involves two eyes, so a one eyed person is less able to judge distance and
depth accurately
● Bad or good?
stereoscopic vision
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