Vision - Special Sense Flashcards
How many sensory receptors are in the eyes?
70%
How much of the cerebral cortex is related to vision?
About 1/2
How are photoreceptors stimulated?
By light, or photons
What structures protect the eye & aid in eye function?
Eyebrows, Cilia- Eyelashes, Palpebrae (eyelids), Conjuctiva, Lacrimal apparatus, Extrinsic Eye muscles
What is Palpebrae?
Eyelids
What is conjunctiva?
Thin membrane that covers & lines the sclera (or white part) of the eye
What is the function of the eyelids?
Protect the front part of the eye
What are the parts of the eyelids?
- Palpebral fissure
- Lacrimal caruncle
- Tarsal Plates
- Levator Palpebrae Superioris
What is the function of the palpebral fissure?
Separates superior & inferior palpebral from each other
when you open your eyes, it’s open, when you close your eyes, it closes
What is the function of the lacrimal caruncle
Makes oil/mucus for the eye
at Medial commissure
What is the function of the tarsal plates?
Internal supporting CT sheet (collagenous sheet for eye)
Levator Palpebrae superioris
Muscle that opens & closes the eyes (gives upper eyelid mobility)
What are the two parts of conjunctiva?
Bulbar & Palpebral
What does the Palpebral conjunctiva line?
The eyelids
What does the bulbar conjunctiva line?
The sclera
What are the two parts of the Iris?
Dilator Pupillae & the Sphincter Pupillae
Dilator Pupillae
Elongated, pulls to dilate pupils
- When exposed to a dark room
- -Sympathetic NS
Sphincter Pupillae
Circular, the muscle constricts to constrict the pupil
- When exposed to a light room
- Parasympathetic NS
What is the posterior Segment?
Vitreous Chamber
- Filled with thick gelatin vitreous humor
FUN FACT!
As you grow older, this jelly isn’t as thiccc and turns into a more liquidated form, pulling on the membrane with the retina and leading to splotchy dots/floaters
What is the anterior segment?
Aqueous Chamber
- Filled with aqueous humor
- 2 Chambers: Anterior & Posterior
What fills the anterior segment with aqueous humor?
Ciliary Processes
What removes the aqueous humor?
Scleral Venous SInus
Where is the Anterior Chamber of the Anterior Segment located?
Between the cornea & iris
Where is the Posterior chamber of the anterior segment located?
Between the iris & lens
What happens during glaucoma?
Increased pressure between retina & optic nerve due to the inability for the aqueous humor to drain
What is the optic disc/blind spot?
Where the optic nerve exits the eye
- No rods or cones are found here
- No photoreceptors here means that whatever light enters thru here cannot be processed, and therefore not seen
What is the macula lutea?
The entire cone shape that includes the fovea centralis in the retina
What is the fovea centralis?
The apex of the cone (macula lutea)
What are the two layers of the eye?
1) Fibrous layer
2) Vascular Layer (Uvea)
3) Inner Layer
What is part of the fibrous layer?
- Sclera
- Cornea
Describe the sclera
Outer white part of the eye
Describe the Cornea
Clear/Transparent
What is part of the vascular layer?
- Choroid
- Ciliary Body
- Ciliary processes, & ciliary muscles
- Ciliary Zonules/Suspensory Ligament
- Iris
What is the choroid?
Brown/black layer that prevents light from scattering/bouncing around too much
(opposite in nocturnal animals, there is a mirror-reflective layer of guanine instead of black to allow light to bounce off the retina and amplify the lights
What is apart of the ciliary body?
Ciliary Processes & Ciliary Muscles
What is the function of the ciliary processes?
To create aqueous humor
What is the function of the ciliary muscles?
Helps change the shape of the lens for focusing
What is the ciliary zonules/suspensory ligament
They hold/suspend the lens of the eye (like rope holding the lens in place)
What is the iris?
Colored part of the eye, controls amount of light entering posterior segment
What is it called when you are checking for responses (constriction) when shining a light in your eye
Accommodation Pupillary Reflex
What are the parts of the inner Layer?
retina (sensory layer/Neural Layer) + pigmented epithelium
What are the parts of the neural layer of the retina?
1) Photoreceptors
2) Bipolar Neurons/Cells
3) Ganglion Neurons/Cells
List the parts of the neural layer of the retina from closes to the light source to furthest away from the light source.
1) Ganglion Neurons/Cells
2) Bipolar Neurons/Cells
3) Photoreceptors
What are the two types of photoreceptors?
Rods & Cones
What are the rods?
Your peripheral vision
- For night-time vision
- Blurry/low resolution
What are the cones?
Day & color perception
- In the macula lutea
- Good focus/resolution (especially at the fovea centralis)
What are the bipolar neurons/cell layer?
Middle layer of retina
- Has horizontal & amacrine cells
- Helps fine-tune images/sharpen images
What are the ganglion Neurons/Cell layer?
Axons that make up the optic nerve
Where do the pigments from seeing come from?
The photoreceptors (there are proteins that read the pigments as colors)
What is the convergence of the eyeballs?
Eyes converge medially to focus close-in; looking straight ahead is the best for focusing
What happens when you shine a low light on someone?
Pupils dilate
- Pupillary Dilator constricts to dilate pupil
- Low light Stimulates sympathetic nervous system
What happens when you shine a bright light on someone?
Pupils constrict
- Light stimulates parasympathetic NS
- Pupillary Constrictor constricts
What is the process of changing the shape of the lens in order to focus the eyes called?
Accommodation of the lens
How does the eyes focus on short distance?
- Ciliary muscles contract
- Leads to the ciliary zone to relax
- Causes the lens to become rounder
- Increases parasympathetic NS
How do the eyes focus in terms of long distance?
- Ciliary Muscles relax
- Ciliary Zones tighten
- Causes the lens to flatten
- Increases sympathetic nervous system
- Decreases Parasympathetic NS Impulses
What is the pigmented epithelium’s function?
Black layer to prevent light from bouncing
