TASTE SMELL AND
HEARING
HCT II
Learning outcomes
Describe the anatomy of the nose and the
function of each part.
Describe how smell sensations are created and
interpreted.
Describe the anatomy of the tongue and the
function of each part.
Describe how taste sensations are created and
interpreted.
Describe the anatomy of the ear and the function
of each part.
Explain the role of the ear in maintaining
equilibrium.
Explain how sounds travel through the ear and
are interpreted in the brain.
State ways that hearing changes with age.
Introduction

Special senses

Sensory receptors located in head
Nose – smell

Tongue – taste

Eyes – vision

Ears – hearing and equilibrium
Touch is a generalized sense



Stimulus  nervous system  brain  response
Nose and Sense of Smell

Olfactory receptors

Chemoreceptors – respond
to changes in chemical
concentrations

Chemicals must be
dissolved in mucus

Located in the olfactory
organ
Nose and Sense of Smell (cont)
Smell sensation
Activation of smell receptors 
information sent to olfactory nerves
that send the information along
olfactory bulbs and tracts
to different areas of the cerebrum;
cerebrum interprets the information
as a particular type of smell
Nose and Sense of Smell (cont.)
• Sensory Adaptation
• Chemical can stimulate receptors for limited time
• Receptors fatigue and stop responding to chemical
• No longer smell odor
• Perfume Test
Apply Your Knowledge
You notice an odor coming from a patient when
you enter the exam room. Why would the patient
not be able to smell it?
ANSWER: After a few minutes, smell receptors undergo
sensory adaptation and no longer respond to the chemical,
and the patient can no longer smell the odor.
Very
Good!
Tongue and Sense of Taste
• Gustatory receptors – located on taste
buds
• Taste buds
• Location
• Papillae of the tongue
• Roof of mouth
}
fewer than on tongue
• Walls of throat
35-11
Tongue and Sense of Taste (cont.)
• Taste cells and supporting
structures
• On taste buds
• Supporting structures fill in space
• Taste cells
• Chemoreceptors
• Chemicals in food and drink must be dissolved in saliva to
activate
Tongue
35-12
Tongue and Sense of Taste (cont.)
• Taste sensation
• 4 primary
• Sweet – tip
• Sour – sides
• Salty – tip and
sides
• Bitter – back
• Spicy foods
• Activate pain
receptors
• Interpreted by brain
as “spicy”
Tongue
35-13
Back
35-15
Apply Your Knowledge
What are the four primary taste sensations and where
are their corresponding taste cells located?
ANSWER: The four primary taste sensations are:
Sweet – concentrated on the tip of the tongue
Sour – concentrated on the sides of the tongue
Salty – concentrated on the tip and sides of the tongue
Bitter – concentrated on the back of the tongue
The Ear and the Senses of Hearing and
Equilibrium: Structures
• External ear
• Auricle (pinna)
• Collects sound waves
• External auditory canal
• Guides sound wave to tympanic membrane
• Contains Cerumen (wax)
• Why do we have wax in our ears?
• Tympanic membrane
• Separates external canal and middle ear
• Vibrates when sound hits it
Ear
• Sound waves travel
through the external
auditory canal to the
tympanic membrane, also
known as the ear drum.
• The tympanic membrane
separates the outer ear from
the middle ear. It vibrates
when sound waves hit it
and sends those sounds to
the middle ear.
The Ear and the Senses of Hearing and
Equilibrium: Structures (cont.)
• Middle ear
• Ear ossicles
• Malleus
• Incus
• Stapes
• Ossicles vibrate in
response to vibration
of tympanic
membrane
• Eustachian tube
• Connects middle ear
to throat
• Equalizes pressure on
eardrum
• Oval window
• Separates middle ear
from inner ear
Ear
*** Sound waves cause the ear drum to vibrate, which is amplified or
increased by the ossicles. Vibration of the stapes against the oval
window causes movement of fluid in the inner ear.
Auditory or Eustachian tube: This is a tube that connects the throat
to the middle ear. It allows air to enter the middle ear and equalizes
pressure in our ears.
Why is it common for an infection in our throat to spread to
our inner ear?
The Ear and the Senses of Hearing and Equilibrium: Structures (cont.)
• Inner ear – labyrinth of communicating chambers
• Semicircular canals – detect balance of the body. This
contains a liquid and delicate hair like cells that bend
with movement. Impulses are sent from the canals to
the vestibular nerve and eventually to the cerebellum of
the brain help to maintain our balance.
• Vestibule – (equilibrium) This acts as a door to the two
other parts of the inner ear.
• Cochlea 2. Cochlea (shaped like a snail): This contains
hair like cells that line the organ of corti (receptor of
sound waves which carries sound waves from the
cochlear nerve to the auditory nerve.) The auditory
nerve carries the message to the temporal lobe, which
interprets the message as hearing.
Ear
• Hearing receptors
• Organ of Corti – organ of hearing
The Ear and the Senses of Hearing
and Equilibrium: Hearing Process
• Sound waves collected
• Waves cause tympanic membrane
to vibrate
• Ossicles amplify vibrations, which
enter inner ear
• Movement of hairs lining cochlea trigger nerve
impulses
• Impulses are transmitted by auditory nerve to
the brain for interpretation
How hearing works
The Ear and the Senses of Hearing
and Equilibrium: Structures (cont.)
• Equilibrium
• Head movement causes fluid in
semicircular canals and
vestibule to move
• Equilibrium receptors transmit
information along vestibular
nerves to cerebrum
• Cerebrum determines if body needs to make
adjustments
How to Recognize Hearing
Problems in Children
• Guidelines
• Infants to 4 months
• Startled by loud noises
• Recognize mother’s voice
• 4 to 8 months
• Regularly follow sounds
• Babble at people
• 8 to 12 months
• Respond to the sound their name
• Respond to “no”
The Aging Ear
• External ear larger / earlobe longer
• Cerumen dryer and prone to impaction
• Ear canal narrower
• Eardrum shrinks and appears dull and gray
• Ossicles do not move as freely
• Semicircular canals less sensitive to changes in position –
affects balance
Apply Your Knowledge
What problem with the aging ear makes the elderly
more prone to falls?
ANSWER: The semicircular canals become less sensitive
to change in position, which affects balance. This problem
with equilibrium results in increased chance of falls in the
elderly.
Great
Answer
!
Hearing Loss
• Symptom of a disease, not a normal part of aging
• Conductive hearing loss • Sensorineural hearing
loss
• Interruption in
transmission to inner ear
• Sound waves not perceived
by brain as sound
• Causes
• Causes
• Obstruction of ear canal
• Hereditary
• Infection of middle ear
• Repeated exposure to
• Reduced movement of
loud noises / viral
stirrup
infections
• Side effect of medication
Infections (otitis):
•
Otitis Media:
•
Otitis Externus
• Otitis Interna
Age Related- look the following conditions up and identify the
causes, signs and treatments if any.
Meniere's Disease
Otosclerosis
Common Diseases and Disorders
Disorder /
Disease
Description
Cerumen
impaction
Build up of wax within external auditory
canal
Hearing loss
Deafness
Meniere’s disease Disturbance in equilibrium characterized
by vertigo and tinnitus
Common Diseases and Disorders
Disorder /
Disease
Description
Otitis
Otitis externa
Otitis media
Otitis interna
Inflammation of the ear
Swimmers’ ear
Middle ear infection; common infection
Labyrinthitis; inner ear infection
Osteosclerosis
Immobilization of the stapes; common
cause of conductive hearing loss
Presbycusis
Hearing loss due to aging process
Treating Ear and Hearing
Problems
• Patient education
• Preventative ear care
• Administer ear medications
• Medications and Irrigation
• Relieve inflammation or irritation of canal
• Loosen and remove impacted cerumen or foreign body
Treating Ear and Hearing
Problems (cont.)
• Hearing aids
• Obtaining a hearing aid
• Otologist – medical doctor
specializing in health of ear
• Audiologist – evaluates and
corrects hearing problems
• Care and use
• Batteries
• Routine cleaning
• Keep dry and avoid hair sprays
• Other devices / strategies
• Amplifiers
• Closed-captioning
• Appliances that light up as
well as ring
Apply Your Knowledge
True or False: ANSWER:
___ An audiologist is a physician that specializes in ear health. otologist
F
___ Otitis media is also called swimmers’ ear.
F
externa
___ Presbycusis is hearing loss due to the aging process.
T
___ Vertigo is ringing in the ears. Tinnitus
F
___ Otitis interna is an inflammation of the labyrinth.
T
___ Meniere’s disease is characterized by disturbances in equilibrium.
T
___ Otosclerosis is the immobilization of the stapes.
T
___ tinnitus is dizziness. Vertigo
F