Specialized cells that are sensitive to light and color
Where are photoreceptors located?
Throughout the retina
Why is the optic disk referred to as the blind spot?
No rods or cones are located there, thus no vision is intercepted there.
Not normally noticeable because of vision of both eyes overlaps.
What are the 3 colors that cones are sensitive to?
What causes color blindness?
Absence of one or more of the cones
What are the most common colors affected by color blindness?
What vitamin is necessary for producing the color pigments of the cones?
Name the structures of the eye through which light must pass to produce vision
2. Aqueous humor
5. Vitreous humor
All of which are colorless. This will produce vision. The light rays then focus on the retina.
What is the macula?
yellow area of the retina
How is the image on the retina transmitted to the brain?
As a nerve impulse through the optic nerve
How does normal aging affect the eye?
Muscles unable to accommodate (move lens)
Lens may become slightly opaque causing difficult vision when glare is present
Pupil becomes smaller with age, more light needed to read
What structure separates the outer ear from the middle ear?
The tympanic membrane
What is the function of cerumen?
Protects inside of ear by trapping dust & foreign material
Describe the location and function of the eustachian tube?
Connects the middle ear with nasopharynx
Equalizes pressure on either side of eardrum
Why is it easy for a throat infection to spread to the ears?
Pathogens can travel up the eustachian tube into the middle ear due to continuous mucous membrane
Children's are shorter and straighter so it's easier to spread
How do sound waves travel through the middle ear?
Ossicles carry sound waves
endolymph & perilymph fluid conduct sound waves from labrynth which is in middle
What are the ossicles of the middle ear?
Malleus, incus, stapes
List the three divisions of the labyrinth?
Semicircular canal, vestibule, cochlea
What is the function of endolymph and perilymph?
Conduct sound waves from middle ear through the inner ear
Explain how the organ of Corti transmits sound waves to the brain?
Contains many hair cells that stimulate the cochlear nerve (part of VIII cranial nerve) in response to sound waves
Cochlear nerve then transmits the sound to the brain for interpretation
List 4 sources of noise that are loud enough to damage the hair cells in the organ of Corti, causing permanent hearing loss
1. Jet Engines
2. Factory equipment
3. Race car engines
4. Loud amplifiers
5. Earphones at high volume
Explain how the semicircular canals maintain balance and equilibrium
Movement of the endolymph w/in semi circular canals stimulates hair cells & sends a message to the brain which interprets balance & equilibrium
How does normal aging affect hearing?
By causing decrease in the ability to distinguish high frequency of sound
Where are the following taste receptors located?
Sweet - tip of the tongue
Sour - Sides of the tongue
Salty - Tip of the tongue
Bitter - Back of the tongue
The tongue is most sensitive to which taste?
Which cranial nerve transmits the messages of taste to the brain?
Where are the olfactory receptors located?
Upper section of the nasal cavity
Why we breathe deeply when we smell a flower
Which cranial nerve transmits the messages of smell to the brain?
Why do certain odors stimulate memories?
Because the brain stores the odor and the events associated with it in long term memory
If olfactory cells are damaged, what will happen to the person's sense of smell?
Sense of smell will be lost since body cannot regenerate olfactory cells
When you have a cold, food does not taste good. Why does this occur?
Because the sense of smell is impaired by nasal congestion. Food does not taste as good when you cannot smell it.
How does normal again affect smell and taste?
Decrease in nerve receptors for smell & taste. Sweet & salty receptors are most affected
What are refractory errors?
Imperfect vision due to the shape of the eyeball or the ability of the eye to focus light rays on the retina.
Give 3 examples of refractory errors
myopia (near sightedness)
hyperopia (fat sightedness)
What is a cataract?
A condition of the eye that interferes with vision because the crystalline lens becomes cloudy. Light rays cannot penetrate the cloudy lens to be focused onto the retina.
List 3 possible causes of cataracts
Trauma to eye
exposure to toxins
inflammation within eye
aging of lens
exposure to sunlight without UV protection
What vision problems might a person with cataracts experience?
sensitivity to light
poor night vision
hazy or fuzzy vision
What is Phacoemulsification when used to remove cataracts?
Ultrasound waves used to break up the clouded lens
small incision is made and pieces of lens are removed through it
Why does a pt who has had a cataract removed have to have a lens implant, wear a contact lens, or wear glasses?
Because crystalline lens of eye is actually removed
Must have to replace lens function
Mr. Sullivan is admitted for outpatient surgery to remove a cataract from his left eye and to have a lens implant done in his left eye. your are caring for him postoperatively. What instructions will you five Mr.. Sullivan to help prevent injury to the operated eye?
HOB raised to 30°
position on back or unaffected side
Return demo of drops & patch changes
report immediately if pain, redness, drainage, or sudden changes in vision
Take stool softener as ordered to prevent increased ICP from straining to have BM
What is the macula?
the point on the retina where light rays meet and focus