Unit Three: Visual System Flashcards
What are the two functions of eyebrows?
- Prevent sweat from dripping into the eye. 2. Shade the eyes from sunlight.
What is the function of eyelashes?
Prevent large foreign objects from contacting the eyes.
Are eyelashes highly innervated?
Yes.
What are eyelids also known as?
Palpebrae.
What is the palpebral fissure?
The opening between the eyelids.
What are tarsal plates and what do they do?
Connective tissue. They help create the structure of the lid and provide attachment for the orbicularis oculi.
What are tarsal glands a modification of?
Modified sebaceous glands.
What are the functions of the tarsal glands? (3)
- Lubricates surface of the eye. 2. Prevent tears from going over the surface of the eye. 3. Prevents eyes from sticking together.
What does the palpebral line?
The eyelid.
What does the bulbar line?
The eye.
What is the conjunctiva?
A transparent mucous membrane made of stratified squamous epithelium.
What are the two segments of the conjuctiva?
- Palpebral. 2. Bulbar.
What kind of cells do conjuctiva contain and what do they do?
Goblet cells that lubricate the surface of the eye.
What is the function of the lacrimal apparatus? (2)
- Produces, collects, and drains lacrimal fluid (tears from the eye. 2. Helps prevent bacterial infections using an antibiotic-like enzyme called lysozyme.
What are the first two initial steps of the tear pathway?
- Lacrimal fluid is produced in the lacrimal gland. 2. Lacrimal fluid is dispersed across the eye surface when blinking.
What happens after lacrimal fluid is dispersed across the surface of the eye? (3) (The final 3 steps of the tear pathway.)
- Lacrimal fluid is drained into lacrimal canaliculi via the lacrimal puncta and collects in the lacrimal sac. 2. Lacrimal fluid drains through the nasolacrimal duct. 3. Enters the nasal cavity.
What nerve causes the production of lacrimal fluid? What kind of innervation is it?
Cranial nerve VII. Parasympathetic.
What is the action of the lateral rectus?
Abduct eye laterally.
What nerve innervates the lateral rectus?
CN VI (Abducens nerve).
What is the action of the medial rectus?
Abduct eye medially.
What is the action of the inferior rectus?
Depress eye.
What is the action of the superior rectus?
Elevate eye.
What is the action of the inferior oblique?
Elevates and abducts eye.
What is the action of the superior oblique?
Depress and abducts eye.
What muscles does CN III (Occulomotor) innervate?
- Medial rectus. 2. Inferior rectus. 3. Superior rectus. 4. Inferior oblique.
What nerve innervates the superior oblique?
Cranial nerve IV (Trochlear).
What nerve causes the pupil to relax? Through what ganglion?
CN III (Occulomotor). Through the ciliary ganglion.
Through what ganglion do nerves contract the pupil? What kind of innervation is this?
Through the superior cervical ganglion. Sympathetic innervation.
What is the function of the ciliary body?
To change the lens shape.
What results in distant vision?
Ciliary muscle relaxing to open diameter, putting tension on suspensory ligaments, which pulls on lens to cause it to flatten.
What is the function of the lens?
To bend light rays that enter the eye.
Where is the anterior chamber of the anterior cavity?
Between the cornea and the pupil.
Where is the posterior chamber of the anterior cavity?
Between the iris and lens.
What do both chambers of the anterior cavity contain?
Aqueous humor.
Is aqueous humor always being produced?
Yes.
What does the vitreous chamber of the posterior cavity contain?
The vitreous body aka the virtuous humor.
What artery is a “true end artery,” meaning there is no collateral circulation?
The opthalmic artery and vein of the retina.
What artery provides the inner 2/3rds of the retina with oxygen and nutrients?
The opthalmic artery.
Is the cornea avascular or vascular? Is it highly innervated?
Avascular. Yes.
What is the outermost layer of the eye?
The fibrous layer.
What does the fibrous layer consist of? (2)
- Sclera. 2. Transparent cornea.
What are the functions of the fibrous layer? (3)
- Provides mechanical support and physical protection of the eye. 2. Serves as an attachment site for the extra-occular muscles. 3. Contains structures involved in the focusing process.
What is the “white of the eye?”
The sclera.
What does the sclera consist of?
Dense, fibrous connective tissue containing collagen and elastic fibers.
What are the functions of the vascular layer? (4)
- Providing a route for blood vessels and lymphatics supplying tissues of the eye. 2. Regulating the amount of light entering the eye. 3. Secreting and reabsorbing the aqueous humor circulating within the eye. 4. Controlling the shape of the lens, which is an essential part of the focusing process.
What 3 structures does the vascular layer include?
- Iris. 2. Ciliary body. 3. Choroid.
Contraction of the muscles of the iris causes what?
A change in the diameter of the pupils.
What is the pupil?
The opening in the center of the iris through which light enters the eye.
What muscle causes the diameter of the pupil to decrease when contracted?
The sphincter pupillae.
What muscle causes the diameter of the pupil to increase when contracted?
The dilator pupillae.
What is the choroid?
The middle, vascular layer in the wall of the eye.
What is the retina?
The inner layer of the eye.
What two layers does the retina consist of?
- An outer thin lining called the pigmented layer. 2. Thicker inner neural layer.
What does the neural layer of the retina contain? (3)
- Photoreceptors that respond to light. 2. Supporting cells and neurons that perform preliminary processing and integration of visual information. 3. Blood vessels that supply the tissues lining the posterior cavity.
What does the pigmented layer of the retina do? (2)
- Absorbs light after it passes through the retina. 2. Has important biochemical interactions with retinal photoreceptors.
What are the two types of photoreceptors?
- Rods. 2. Cones.
Do rods detect different colors of lights?
No.
What is the function of rods?
To enable us to see in dimly lit rooms.
What is the function of cones?
To detect different colors and, therefore, provide us with color vision.
Which provides us with clearer, sharper images, but requires more intense light?
Cones.
What region has no rods?
The macula.
Where is the highest concentration of cones?
The fovea centralis, which is in the middle of the macula.
What are the first order neurons in the optic pathway?
Ganglion cells.
What do bipolar cells synapse with? (2)
- Ganglion cells on the anterior side. 2. Photoreceptors on the posterior.
Where do axons of the ganglion cells converge?
On the optic disc.
Where is the origin of the optic nerve (II)?
The optic disc.
Where is the blind spot?
Where the optic disc is.
What do the nasal retinas allow for?
Periphery visual information.
What do the temporal retinas allow for?
Middle of visual field information.
Which retinas cross?
Nasal retinas.
Where do the nasal fibers of the retinas cross?
At the optic chiasm.
Once the neural fibers are passed the optic chiasm, what begins?
The optic tract.
After becoming the optic tract, where does the second synapse begin?
At the lateral geniculate nucleus of the thalamus.
After the lateral geniculate nucleus, where do axons travel?
Through optic radiations to the primary visual cortex in the occipital lobe.
In which Brodmann’s area is the primary visual cortex?
BA 17.
What does the primary visual cortex do?
Receives and processes incoming visual information.
What is the function of the posterior calcarine cortex of the primary visual cortex?
High resolution.
What is the function of the anterior calcarine cortex of the primary visual cortex?
Peripheral vision.
What does the right visual cortex process? (2)
- Right half of each retina. 2. Left visual field.
What does the left visual cortex process? (2)
- Left half of each retina. 2. Right visual field.
In which Brodmann’s area is the visual association areas?
BA 18.
What is the function of the visual association areas?
To continue processing visual information.
When do the neural fibers to the visual association areas branch off?
Before the lateral geniculate nucleus.
What is the function of the suprachiasmatic nucleus?
Information about light and dark for the circadian rhythm (sleep/wake cycle).
What is the function of the Edinger-Westphal nuclues?
Pupillary reflex and lens control.
What is the function of the superior colliculus?
Orienting movements of the head and eyes and reflexively directing the eyes to areas of interest.
Where is the Edinger-Westphal nuclues and superior colliculus located?
In the midbrain.
Where is the suprachiasmatic nuclues located?
In the hypothalamus.
Where are the visual association areas?
Parts of the temporal and parietal lobes.
What does V4 do?
Adds color vision.
What does V5 do?
Adds motion sensitivity.
What can V4 impairment lead to?
Impaired color discrimination.
What can V5 impairment lead to?
Cerebral akinesia. Impaired motion detection.
What can impairment in the fusiform face area lead to?
Inability to recognize faces.
What can impairment in the inferotemporal complex lead to?
Inability to attach emotion to visual stimuli.
What can impairments in the parietal regions lead to?
Visuospatial neglect.
Where is the primary visual cortex located?
In the calcarine fissure (sulcus).
What is dorsal stream process also known as?
The “where” pathway.
What is the ventral stream process also known as?
The “what” pathway.
What is the middle temporal gyri involved in? (3)
Contemplating distance, recognition of known faces, and accessing word meaning while reading.
What is the inferior temporal gyri involved in?
The ventral stream.
Where is the posterior cavity?
Between the lens and retina.
