12.2 Photo Reception Flashcards
What are the 3 layers of the eye?
External
Intermediate
Internal
What is the the for the external layer of the eye?
Sclera
What is the Sclera?
The white, tough, fibrous, external layer of the eye
Where does light enter the eye?
Through the cornea
What is the Cornea?
The transparent part of the Sclera at the front of the eye
What is the intermediate layer of the eye called?
The Choroid
What does the Choroid do?
Absorbs stray light rays that are not detected by photoreceptors. also contains blood vessels to nourish the eye
What does the Choroid form toward the front of the eye?
the Iris
What does the Choroid do behind the Iris?
The Choroid thickends and forms the ciliary muscles
What does the ciliary muscle do?
Attaches to the lens which focuses images on the retina
What is the internal layer of the eye called?
The Retina
What is the Retina?
A thin layer of tissue that contains photoreceptors- Rods and cones
What are Rods sensitive to?
Light intensity
What are Cones sensitive to?
Different colors
Where are the Cones found?
Packed more densely at the back of the eye called Fovea Centralis
How do Rods and Cones send sensory impulses?
Through the Optic Nerve
What does the lens do to the eye?
Divides the eye into 2 chambers
What is the Anterior chamber?
The front of the lens
What is the Posterior Chamber?
The back of the lens
What is found in the Anterior Chamber?
A clear watery fluid called the Aqueous Humour
What does the Aqueous Humor do in Anterior Chamber?
Maintains cell shape of the cornea and provides oxygen and nutrients to the surrounding cells including the lens and cornea
What happens if the ducts that empty out the Aqueous humor are clogged?
Pressure can build up in the eye causing the delicate blood vessels to rupture leading to glaucoma, which leads to blindness
What is the Posterior Chamber surrounded by?
The Retina
What does the Posterior Chamber contain?
Clear jelly like fluid called Vitreous Humor
What does the Vitreous Humor do?
Helps to maintain the shape of the eyeball and supports the surrounding cells
What does the external layer contain?
The Cornea
What does the Intermediate layer contain?
Sides and back of Choroid
Iris
Pupil
Ciliary Muscles
What does the Internal layer contain?
Rods
Cones
Fovea Centralis
What does the Sclera do?
Protects and supports the eyeball
What does the Cornea do?
Bends light rays into the eye
What does the Choroid do?
Absorbs scattered light and contain blood vessels
What does the Iris do?
Regulates the amount of light that enters the eye
What is the Pupil?
The opening for light to enter the eye
What do the Ciliary muscles do?
Changes the shape of the lens in order to focus
What are Rods?
Photoreceptors that are sensitive to light
What are Cones?
Photoreceptors that are sensitive to color
What does the lens do?
Focusses light rays onto the Fovea Centralis
What do the Humours do?
Support the eyeball with the pressure of fluids they contain
What does the optic nerve do?
Transmits sensory information to the brain
How is the image that is protected on the Fovea Centralis different than the actual object?
The image is smaller, upside down, and reversed from left to right
How do the Ciliary muscles act when the object is far away?
The ciliary muscles relax and suspensory ligaments become taut causing the lens to flatten
How do the Ciliary muscles act when an object is nearby?
The Ciliary muscles contract and the suspensory ligaments relax causing the lens to become rounded
What is accomodation in the eye?
The ability of a lens to change shape in order to focus images clearly on the retina
What is Cataracts?
When the protein structure in the lens starts to degenerate making it opaque and unable to have light pass through
What is Astigmatism?
An uneven curvature on part of the cornea so it can not bend light rays so they meet the correct focal point
What is Myopia?
Nearsightedness
What is different in people with Myopia?
They eyeball is elongated so focussed light falls in front of the retina
How is Myopia fixed?
Concave lenses
What is Hyperopia?
Farsightedness
What happens in Hyperopia?
The eyeball is short so light rays do not meet before they reach the retina
What can fix Hyperopia?
Convex lenses
Which photoreceptor responsible for Peripheral vision?
Rods
Why does Peripheral vision lack color?
Due to the location of the Fovea Centralis and where the cones are
What allows us to read?
Cones
What is different about the 3 types of cones?
They each absorb a different wavelength of light
What is color blindness caused by?
Lack or deficiency of a type of cones
What do Rods contain?
A light absorbing pigment called rhodopsin which is composed of retinal and the protein opsin
What do Rods release in the dark?
An inhibitory transmitter that inhibits nearby nerve cells
What happens when Rods absorb light?
Rhodopsin splits into retinal Opsin. which stops the release of the inhibitory neurotransmitter allowing a transmission of the nerve impulse to the optic nerve
What happens when light stimulates the rods and cones?
They stop releasing an inhibitory neurotransmitter into the synapse
What happens when rods and cones stop releasing an inhibitory neurotransmitter into the synapse?
Bipolar cells then transfer a neural impulse to the ganglion cells. The axons of the ganglion cells form the optic nerve. An transmit the image to the occipital lobe of the brain
Why is there a blind spot?
Because this is where the ganglion cells merge to form the optic nerve
Why don’t we normally see the blind spot?
Because each eye compensates for the visual information that the other misses
Where is visual information processed?
The Cerebrum
What happens in diabetic retinoplasty?
Capillaries in the retina burst spilling blood into the vitreous fluid and the retina
What is retinal detachment?
When the retina becomes detached from the Choroid vessels that supply it with nutrients and oxygen
What is macular degeneration?
When the cones are destroyed due to thickened choroid vessels. Resulting in a blind spot of central vision
