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Lecture Outline
I. Introduction
A. All input from the environment must be taken in by the senses and interpreted
by the brain to be understood and appreciated
1. Sensory receptors detect changes in the environment and then send this
information to the brain via sensory (afferent) neurons
2. The brain interprets the information and then makes an appropriate motor
(efferent) response
B. There are many different types of senses
1. Special senses
a. Found in well-defined regions of the head
b. Examples of special senses:
i. Sight (eyes)
ii. Hearing and balance (ears)
iii. Smell (nose)
iv. Taste (tongue)
2. General senses
a. Have sensory receptors that are scattered throughout various regions of
the body
b. Examples of general senses:
i. Pressure or touch
ii. Pain
iii. Temperature
iv. Hunger
v. Thirst
vi. Nausea
3. Cutaneous senses
a. Have sensory receptors located in the skin
b. Examples of cutaneous senses:
i. Touch
ii. Heat
iii. Cold
iv. Pain
4. Visceral senses
a. Have to do with perception of the internal organs
b. Examples of visceral senses:
i. Hunger
ii. Thirst
iii. Nausea
iv. The need to urinate
v. The need to defecate
II. Sight
A. Overview
1. The eye has many similarities to a camera
a. Light rays from an image pass through an opening at the front of the eye
called the pupil (similar to the opening that lets light in a camera)
b. They then pass through the transparent lens, which focuses them
(similar to the lens of a camera)
c. The light rays are then projected on the retina (which is like the film of a
camera, detecting the image)
d. The iris allows the right amount of light to enter the eye for proper
focusing (similar to the shutter on a camera)
e. External structures of the eye help to provide protection (like a camera’s
case protects the camera)
f. Tears secreted from the lacrimal gland help to keep the lens clean (like
cleaning the lens of a camera)
B. External structures of the eye
1. The orbit is a cone-shaped cavity formed by the skull; it houses and
protects the eyeball and is padded with fatty tissue that acts as a cushion
to prevent injury
2. Six short muscles connect the eyeball to the orbit and allow rotary
movement to see in all directions
3. The eyelids close over the eye to protect it from light, foreign particles, and
impact injuries
a. Eyelashes attached to the eyelid help to prevent large particles from
entering the eye
b. The eyelids also contain sebaceous glands that secrete sebum to keep
them soft, pliable, and slightly sticky to trap particles
4. The conjunctiva is a protective membrane that lines the inner eyelid and
covers the exposed surface of the eyeball, protecting the eye’s surface
5. The lacrimal apparatus produces and stores tears
a. The lacrimal apparatus includes the lacrimal gland and its corresponding
ducts
b. The lacrimal gland produces tears that clean, lubricate, and act as an
antiseptic
i. Tears are constantly being produced
ii. They are spread over the eye by blinking
c. Tears drain out of the eye through two small openings in the inner
corner of the eye
i. They eventually drain into the nose
ii. When you cry (and produce excess amounts of tears), the extra
drainage into the nose is what causes your nose to run
C. Internal structures of the eye
1. The globe-shaped eyeball is the organ of vision and is separated into two
chambers of fluid that help to protect the eye
a. The fluids of the eye are called humors:
i. Aqueous humor is watery and fills the area in front of the eye,
where it bathes the iris, pupil, and lens
ii. Vitreous humor is a clear, jellylike fluid that occupies the cavity
behind the lens
2. The eyeball has three layers: the sclera, choroid, and retina
a. Sclera—the outermost layer
i. A tough, fibrous tissue that serves as a protective shield
ii. Has a white appearance (“whites of the eye”)
iii. Cornea is found in this layer
• This transparent area allows light to pass into the eye
• Its curve begins to focus the entering light on the retina
b. Choroid—the middle layer
i. A highly vascularized and pigmented region
• Provides nourishment to the eye
• Prevents internal reflection of light rays
ii. Contains the iris and the pupil
• The pupil is the opening that allows light into the eye
• The iris is the colored portion of the eye
• It is a muscular sphincter that controls the size of the pupil
• In low light it relaxes, allowing the pupil to dilate so more light
can enter; in bright light the pupil constricts, causing less light
to enter the eye
c. Retina—the innermost layer
i. Contains nerve endings that receive and interpret the rays of light
ii. Contains two types of light-sensing receptors
• Rods
• Active in dim light
• Do not perceive color
• Cones
• Active in bright light
• Perceive color
iii. Each eye contains millions of sensory receptors, including
• About 100 million rods
• About 3 million cones
iv. Transmission and interpretation of visual information
• The sensory receptors (rods and cones) contain photopigments
• When light hits them, a chemical change occurs
• This chemical change causes an impulse to be sent through the
optic nerve to the brain
• In the cerebral cortex of the occipital lobe, the impulse is
interpreted and we “see” the object
3. Other structures of the eye
a. Lens—a clear disc located just behind the pupil
i. Surrounded by the ciliary muscles, which can alter the shape of the
lens
• Ciliary muscles can make the lens thinner or thicker to help focus
light rays on the retina
4. Accommodation
a. The process that combines changes in the size of the pupil and shape of
the lens to properly focus an image
D. Pathology Connection: Injuries and Disorders of the Eyes
1. Stye (Hordeolum)—Abscess formed at the base of an eyelash due to
infection of a sebaceous gland
a. Resembles acne pimples (red, swollen, and painful)
b. Can be the result of a bacterial infection
2. Conjunctivitis—inflammation of the membrane that lines the eye
a. Characterized by red, swollen eyes (sometimes called pinkeye)
b. Possible causes of conjunctivitis:
i. Irritants (like fumes or onions)
ii. Pathogens (like viruses or bacteria)
• Examples:
- Staphylococcus aureus
a. An acute infection
- Chlamydia trachomatis
a. Tends to cause more chronic infection (called trachoma)
c. Viral and bacterial conjunctivitis are often highly contagious
3. Cataract—clouding of the lens; lens losses its flexibility and transparency
a. Possible causes:
i. Congenital defects
ii. Trauma
iii. Aging
iv. Increased sunlight exposure may speed up the development of
cataracts
b. Untreated, can lead to blindness
c. Typical treatment—surgery
i. Cataract surgery was one of the earliest surgical procedures, dating
back to ancient Greece
4. Glaucoma—increased pressure in the fluid of the eye, which interferes with
optic nerve function
a. Vision gradually deteriorates
i. Peripheral vision is reduced first
ii. Later, tunnel vision develops
iii. Blindness can eventually develop
b. Epidemiology of glaucoma
i. Occurs in 20% of adults over 40
ii. Accounts for 15% of blindness in America
c. Can be easily diagnosed
d. Treatments include medication and surgery
5. Macular degeneration—a condition that causes the loss of central vision
(peripheral vision is unaffected)
a. Two forms
i. Atrophic (dry)—has no cure
ii. Exudative (hemorrhagic)—can be improved slightly with argon laser
therapy
6. Retinopathy—damage to the retina
a. Can be caused by systemic diseases like hypertension or diabetes
mellitus
b. Smoking can further aggravate this condition
c. Can result in vision impairment or blindness
7. Refractive errors—abnormalities in the eye’s ability to focus
a. Conditions involving improperly focused light rays on the retina
i. Hyperopia—Close objects appear blurred (farsightedness)
ii. Presbyopia—farsightedness that occurs with age
• Caused by age-related changes in the eye:
- Ciliary muscles weaken
- Lens becomes stiff and yellowish
- Pupil size decreases, reducing the amount of light coming into
the retina
• Results in farsightedness and increased sensitivity to glare
(which can make night-driving difficult)
• Typically begins between 40 and 45 years of age
iii. Myopia—objects at a distance appear blurred (nearsightedness)
b. Treatments for refractive errors
i. Glasses
ii. Contact lenses
iii. Surgical techniques
• Radial keratotomy (RK)—incisions are made around the cornea
to reshape the eyes
• In situ keratomileusis (LASIK)—lasers are used to reshape the
corneal tissue
8. Amblyopia—also called lazy eye
a. Occurs in childhood
b. Results in poor vision because one eye does more work than the other
c. Treatments may include covering the dominant eye to force the weak
eye to work, usage of corrective lenses, or surgery
9. Diplopia—double vision
a. Occurs when one eye is not aligned with the other eye
b. Treatments may include placing a patching over the misaligned eye,
using special corrective lenses, realigning the misaligned eye surgically,
or treating the nonocular disease that may be causing diplopia
10. Strabismus—misalignment of one eye due to the inability of the muscles of
the eye to coordinate movement with the other eye
a. Can result from a congenital defect, injury, or disease
b. Treatments may include corrective lenses, exercises, or surgery to
modify the affected muscles
11. Nyctalopia—difficulty seeing at night or in dim light
a. Often caused by vitamin A deficiency
b. Vitamin A is needed to make the photopigments in rod cells
12. Red-green color blindness
a. The inability to distinguish between the colors red and green
b. Caused by a genetic defect carried on the X chromosome
i. Causes more men to get the disorder
c. Diagnosed with colored figures that require patients to distinguish
between various colors
E. Using the eyes to diagnose nonvisual diseases
1. Yellow tint to the conjunctiva (jaundice) can indicate liver disease
2. Responsiveness of the pupil to light (neurological assessment) can help to
determine the presence of a brain injury
a. The results of a normal assessment are abbreviated PERLA (which
stands for pupils equal, round, reactive to light and accommodation)
3. Rapid eye movement (REM) is a stage of sleep and can be measured in
sleep studies to help diagnose sleep disorders
III. Hearing
A. Overview
1. The ear is responsible for hearing and maintaining equilibrium, or sense of
balance
2. Overview of sound transmission
a. Sound vibrations are received by the ear
b. The sound vibrations cause a nerve impulse to be sent through the
vestibulocochlear nerve (cranial nerve VIII) to the brain
c. The temporal lobe of the brain then interprets the impulse as sound
3. Although most sounds reach our ears through the air, sounds can also be
transmitted through liquids and solids
a. Sound is transmitted by molecular collisions
b. In solids and liquids, the molecules are actually closer together, so
sound vibrations are more easily transmitted
c. This is why:
i. Whales can communicate through the water over distances of up to
two miles
ii. Trapped miners tap on the wall instead of shouting for help
B. Structures of the ear
1. The ear has three divisions:
a. The external (outer) ear
b. The middle ear (tympanic cavity)
c. The inner ear (labyrinth)
2. External (outer) ear
a. Pinna (auricle)—the projecting part of the ear
b. Auditory canal (external auditory meatus)—the canal that contains
earwax and leads to the tympanic membrane
c. Ceruminous glands—secrete cerumen (earwax), which lubricates and
protects the ear
d. Tympanic membrane (eardrum)—located at the end of the auditory
canal
i. Vibrates when struck by sound waves
ii. Marks the end of the external ear
3. Middle ear (Tympanic cavity)
a. Ossicles
i. Three tiny bones of the ear:
• Malleus (hammer)—attached to the tympanic membrane
• Incus (anvil)—attached to the hammer
• Stapes (stirrup)—connects to a membrane called the oval
window that begins the inner ear
ii. Function of the ossicles—to amplify sound waves received by the
tympanic membrane and transmit them to the inner ear
• Ossicles can amplify sound up to 22 times the original level
b. Eustachian tubes
i. Connect the pharynx to the middle ear
ii. Allow for the equalization of air pressure on either side of the
eardrum
iii. Equalization of pressure allows eardrum to vibrate freely with
incoming sound waves
iv. Sudden pressure changes, as when flying in an airplane, can affect
this area
• People are advised to chew gum or swallow so the inner ear can
better sense and adjust to the rapidly changing outside
atmosphere via the Eustachian tubes
4. Internal ear (Labyrinth)
a. The oval window is the portal to the inner ear
i. It transmits sound waves into the inner ear
b. The inner ear is divided into three separate, hollow bony spaces that
form a maze, or labyrinth. These areas include the:
i. Cochlea
ii. Vestibule chamber
iii. Semicircular canals
c. Cochlea—responsible for sensing sound
i. Shaped like a bony spiral or snail shell
ii. Connected to the oval window membrane
iii. Contains fluids called perilymph and endolymph
• When the ossicles hit the oval window, the perilymph in the
cochlear duct helps to transmit the sound vibrations
• The sound is transmitted to the endolymph in the back of the
cochlea
• The fluid vibrations of the in the back of the cochlea are picked up
by tiny hairlike receptors of the organ of Corti
• When the receptors of the organ of Corti vibrate, they send a
signal through the acoustic (auditory) or vestibulocochlear nerve
(cranial nerve VIII) to the brain
iv. Hearing and conduction of sound
• Hearing begins with sound conduction
- Sound waves enter the auditory canal
- They hit the tympanic membrane, causing it to vibrate
• Then bone conduction occurs
- The movement of the tympanic membrane causes the ossicles
to vibrate, amplifying the vibration
• Finally, sensorineural conduction occurs
- The ossicles strike the oval window, transmitting the vibration
to the fluid inside the cochlea
- The vibrating cochlear fluid stimulates the hairlike nerve cells
of the organ of Corti
- The stimulation of the hairlike nerve cells of the organ of Corti
causes a nerve impulse to be sent through the
vestibulocochlear nerve (cranial nerve VIII) to the temporal
lobe of the brain
- In the temporal lobe of the brain, the nerve impulse is
interpreted as sound
v. Hearing damage
• Intense, loud noises (like gunshots) may cause the hairlike
sensory cells to topple over
• Repeated assaults can cause permanent hearing damage
• Therefore, it is important to wear hearing protection when
exposed to loud noises
d. Semicircular canals—process sensory input related to equilibrium
(balance)
i. Consist of three loops that are filled with endolymphatic fluid and
contain hairlike sensory receptors
ii. Changes in body position cause the fluid in the canals to move
iii. This movement stimulates a sensory receptor, which sends a nerve
impulse through the vestibulocochlear nerve (cranial nerve VIII)
iv. The nerve impulse reaches the cerebellum and brain stem, where it
is interpreted as body position to help maintain equilibrium
C. Pathology Connection: Diseases of the Ear
1. External otitis—infection in the ear canal (caused by bacteria or fungi)
a. Also called “swimmer’s ear”
b. Symptoms—pain, fever, temporary hearing loss
c. May be contracted from contaminated swimming pools and beaches
d. Can be prevented by:
i. Cleaning and drying the external ear after swimming
ii. Wearing ear plugs
2. Otitis media—infection of the middle ear (caused by a bacteria or virus)
a. Commonly found in infants and children
b. Usually associated with a cold or other upper respiratory infection (URI)
c. Symptoms—pain, edema, and pus; in some cases the eardrum may
rupture
d. Treatments—if infection is bacterial, treat with antibiotics; if recurrent
and chronic, the patient may undergo a myringotomy (surgical insertion
of tiny tubes in the tympanic membrane to relieve pressure)
3. Mastoiditis—infection of the mastoid process (honeycombed sinus area)
a. There is potential for an ear infection to spread to the mastoid process in
the nearby sinus area
i. When this happens it is called mastoiditis
ii. Mastoiditis can lead to brain infections
b. A sinus infection (sinusitis) can also spread to the ear and cause an ear
infection
4. Labyrinthitis—inflammation of the inner ear
a. Often caused by an infection
b. May result in vertigo—a feeling of dizziness or whirling in space
5. Ménière’s disease—a chronic condition that affects the inner ear
a. Characterized by progressive hearing loss and vertigo
6. Otosclerosis—Chronic, progressive middle ear disorder
a. Characterized by excessive bone growth in the middle ear (primarily
affecting the stapes)
b. Because the stapes becomes immobile, this condition can result in
ringing in the ear(s) and deafness
c. May be treated with stapedectomy surgery, where the stapes is
removed and replaced with a plastic or wire substitute
7. Tinnitus—a ringing, roaring, buzzing, hissing, or clicking sound in the ear(s)
a. Symptom of sensorineural hearing loss (affects approximately one out of
every five people)
b. Caused by bent or broken hairs of the inner ear(s) sending random
electrical impulses to the brain
c. The sound may be produced by the brain to compensate for the lack of
sounds no longer heard due to hearing loss
d. Possible result of chronic exposure to loud noises, age-related hearing
loss (presbycusis), stress/depression, Ménière’s disease, some
medications (including certain antibiotics and cancer medications), wax
buildup, or various disturbances to the auditory nerve
e. Caffeine, alcohol, and chocolate may intensify the sounds
IV. Taste
A. The sense of taste is called the gustatory sense
B. Taste receptors (taste buds) are located on the tongue, lips, and back of the
throat
C. The five tastes detected by the taste buds are sweet, sour, salty, bitter, and
umami, which identifies the taste of glutamates (often found in Asian cuisine)
D. Taste preferences may change with the body’s needs (for example, food
cravings in pregnant women)
E. Refinement of food taste is primarily dependent on the sense of smell
V. Smell
A. The sense of smell arises from the receptors located in the olfactory region or
the upper part of the nasal cavity
B. We “sniff” to bring the smell into the nose where tissues (olfactory epithelium)
interpret the scent
C. Taste and smell are closely related (which is why foods taste bland when you
have a severe head cold)
D. Pleasant food odors initiate digestive enzymes
E. Smell is closely related to memory and has been shown to trigger memories
F. Rhinitis—inflammation of mucous membranes that line the nasal passage
1. Characterized by congestion and drainage of the nasal passage
2. May be caused by viral infections, bacterial infections, allergies, harsh
odors, and the use of certain illegal drugs
3. Condition develops in response to the release of histamine (a molecule
released during an immune response)
4. Treatments—Removing the irritant causing the reaction, antihistamine
medications, or surgery to clear nasal obstructions (in chronic cases)
VI. Touch
A. Touch receptors (tactile corpuscles) are small, rounded bodies located in the
skin
B. They are especially concentrated in the fingertips and the tip of the tongue
C. Deep touch receptors are responsible for detecting pressure on the skin
1. This is why patients who are under local anesthesia (awake—like during
dental work) can still feel pressure, even though they do not feel pain
D. Temperature
1. Temperature sensors are also located in the skin
2. There are separate sensors for heat and cold
3. Temperature sensors are some of the sensors in the body that may
demonstrate adaptation
a. Adaptation occurs when sensory stimulation is continually applied;
sensors may eventually desensitize or adapt
i. Example of temperature adaption is illustrated when first jumping
into a hot bath; the water may seem very hot, but after a few
seconds the water does not feel as hot (even though the water
temperature is still the same)
4. Clinical Application: Heat and Cold Therapy
a. These therapies rely on the body’s physiological response to either heat
or cold
b. Heat relaxes muscles and dilates blood vessels, bringing more blood
flow to the site of injury
c. Cold constricts blood vessels and minimizes the amount of blood and
swelling at the site of injury
E. Pain
1. Pain is a very important protective sense (the body’s way of making us pay
attention to a particular danger)
2. Pain is the most widely distributed sense, found in skin, muscle, joints, and
internal organs
3. Pain receptors are branching nerve fibers called nociceptors (free nerve
endings)
4. Types of pain:
a. Referred pain—originates in an internal organ and is felt in another
region of the skin
i. Occurs because internal organs are not well mapped on your
somatic sensory cortex
• Example: liver and gallbladder pain may be felt in the right
shoulder
b. Phantom pain—pain felt in an area where a body part had been
attached, a type of pain that may occur following an amputation
5. Pain receptors
a. Pain receptors do not adapt
i. Unless under anesthesia, pain is felt as long as the stimulus is
there
b. An interesting debate is whether or not some people have higher or
lower thresholds of pain
F. Proprioception
1. Proprioception is the sense of body orientation
a. Examples:
i. The ability to point to a body part with your eyes closed
ii. The ability to know your arm is raised without seeing it
2. Proprioceptors are found in muscles, tendons, joints, and the inner ear
(where they help with equilibrium)
3. Motion sickness (car sickness or seasickness) results from excessive
stimulation of the equilibrium receptors in the ear
VII. Common Disorders of the Eye and Ear
A. Disorders of the eye
1. Astigmatism
a. Etiology—Alteration in the shape of the cornea in which it becomes
more oblong or football shaped than spherical. Usually hereditary but
can result from eye injury
b. Signs and symptoms—Blurred vision, eyestrain and headaches
c. Diagnostic tests—Eye exam to view shape of cornea
d. Treatment—Unless extreme, it can be treated with eyeglasses or
contact lenses. If extreme, refractive eye surgery
2. Amblyopia (lazy eye)
a. Etiology—Eye trauma or strong refractive error (nearsightedness or
farsightedness); generally develops in young children
b. Signs and symptoms—Squinting or completely closing one eye to see,
poor vision, eyestrain, and headaches
c. Diagnostic tests—History and eye exam
d. Treatment—Patching stronger eye to force weaker eye to function
better, atropine eye drops, correcting refractive problems or surgery
3. Blepharitis
a. Etiology—Inflammation of eyelids, usually caused by bacterial infection
b. Signs and symptoms—Eye irritation, burning, tearing, dryness, and
foreign body irritation
c. Diagnostic tests—History and eye exam
d. Treatment—Warm compresses, cleansing the eyes, antibiotics, artificial
tears, and sometimes steroids
4. Cataracts
a. Etiology—Clouding of the lens usually caused by protein clumping
together as we age; cause unknown but excessive UV light exposure
suspected; diabetics are at higher risk; frequently occurs in people over
70
b. Signs and symptoms—Painful, gradual blurring and loss of vision
c. Diagnostic tests—Eye exam
d. Treatment—In early stages, glasses or magnification aids may help.
Surgical correction of the lens is indicated when vision is seriously
impaired
5. Color blindness
a. Etiology—Not really blindness at all but a deficiency in the way we see
color; red-green color deficiency is most common form; caused by
retinal cells’ inability to respond to certain colors; usually hereditary via
the mother, and more common in males; aging and disease can also be
causes
b. Signs and symptoms—Difficulty distinguishing red from green or blue
from yellow
c. Diagnostic tests—Ishihara plates (see Figure 11–4)
d. Treatment—No cure but needs to be recognized early to prevent
developmental issues
6. Conjunctivitis (pinkeye)
a. Etiology—Inflammation of the conjunctiva membrane caused by
bacteria, virus, or allergies
b. Signs and symptoms—Pinkish eye, discharge, excessive eye watering,
pain, and itching
c. Diagnostic tests—History, eye exam and culture, and sensitivity
d. Treatment—Avoidance of cause and infection precautions; warm
compresses; antibiotic eye drops for bacterial infections and
antihistamines for allergic forms
7. Diabetic retinopathy
a. Etiology—High blood sugar damages the blood vessels in the eyes;
later stages can have new blood vessel growth over the retina, which
can cause scar tissue and lead to retinal detachment; if untreated can
cause blindness
b. Signs and symptoms—Floaters, double vision, fluid leakage, and
swelling
c. Diagnostic tests—Fluorescein angiography; a contrast dye is injected,
and the blood flow to the retina is then assessed
d. Treatment—Laser photocoagulation to seal leaking blood vessels and
destroy new growth; some drugs helpful in early stages; may be
prevented by good blood sugar control
8. Dry eye syndrome
a. Etiology—Chronic lack of eye lubrication and moisture due to lack of
tear production; can be part of aging process, side effect of medications,
climate related (dry, dusty, or windy), long-term contact use, lack of
blinking, or certain disease states; more common in women; smoking
increases risk
b. Signs and symptoms—Dryness, scratchiness, and burning
c. Diagnostic tests—History and eye exam
d. Treatment—Avoid irritating cause; when prevention or cure not possible,
artificial tears (lubricating eye drops) can be used to alleviate symptoms
B. Disorders of the ear
1. External otitis (swimmer’s ear)
a. Etiology—Commonly caused by infection from water contaminated by
bacteria or fungi
b. Signs and symptoms—Pain, fever, and temporary hearing impairment
c. Diagnostic tests—Visual ear exam
d. Treatment—Prevention by cleaning and drying external ear after
swimming or by wearing ear plugs
2. Otitis media
a. Etiology—Acute infection of the middle ear, usually caused by a bacteria
or virus; commonly associated with an upper respiratory infection (URI)
such as a cold
b. Signs and symptoms—Pain, edema, pus; if left untreated can perforate
the tympanic membrane; there is potential for invasion of nearby
mastoid process, leading to mastoiditis
c. Diagnostic tests—Otoscopic examination
d. Treatment—Treatment of underlying infection; use of antibiotics if
identified as bacterial infection
3. Labyrinthitis
a. Etiology—Inflammation of the inner ear usually caused by high fevers
b. Signs and symptoms—Vertigo; feeling of dizziness or whirling in space
c. Diagnostic tests—Patient history, radiologic studies
d. Treatment—Antivert class drugs, and in many cases Benadryl has been
successful
4. Ménière’s disease
a. Etiology—Chronic condition that affects the labyrinth
b. Signs and symptoms—Progressive hearing loss, tinnitus, and vertigo
c. Diagnostic tests—Patient history and exam; audiologic and radiologic
exams
d. Treatment—Diuretics to “dry” out the labyrinth, decrease caffeine
consumption
5. Tinnitus
a. Etiology—Can occur as a result of chronic exposure to loud noises,
Ménière’s disease, some medications, wax buildup or various
disturbances to the auditory nerve
b. Signs and symptoms—Ringing in ears
c. Diagnostic tests—History
d. Treatment—Eliminate loud noises
VIII. Pharmacology Corner
A. Drugs that affect the eyes
1. Mydriatic agents—Dilate the pupils
a. Example—Atropine
b. Used in eye examinations to allow for better visualization of the inner
eye
c. After the exam, patients need to wear sunglasses because their pupil(s)
cannot react to bright light until the drug wears off
2. Miotic agents—Constrict the pupils
a. Example—narcotic drugs; sometimes the constriction is so tight that the
pupils look like pinpoints
3. Topical antibiotics (liquid drop and salve form)—used for eye infections
B. Ear medications
1. Topical antibiotics—used for ear infections
2. Topical anesthetics—can be used for severe ear pain (like the pain
experienced from swimmer’s ear)
C. Medication for motion sickness
1. Antivert—affects the neural pathways that originate in the labyrinth
a. Inhibits nausea and vomiting caused by motion sickness