THE EAR
And other senses
LET’S TEST YOUR HEARING….
https://www.youtube.com/watch?v=G-88Vzj0AlA
SENSE 2: HEARING (AUDITION)
 The loudness of a sound is determined by a waves amplitude
(height.)
 The frequency, number of complete wavelengths that pass a
point in a given time, determines the sounds pitch: the tones
highness or lowness.
HEARING THRESHOLD
Hearing is
measured in
decibels.
Zero
decibels is
considered
the threshold
of hearing.
PARTS OF THE EAR
 Outer Ear:
 Job: Gather sound waves to eardrum.
 Parts: auditory canal and eardrum.
 Middle Ear
 Job: To Amplify and concentrate the vibrations onto cochlea’s oval
window.
 Parts: Ossicles, made up of three tiny bones: hammer, anvil, and
stirrup (malleus, incus, and stapes)
 Inner Ear
 Job: To change sound waves into neural impulses
 Parts: Oval Window, Cochlea, Basilar Membrane, Hair Cells.
PROCESS OF HEARING
1.
Your outer ear channels
sound waves to the eardrum
or tympanum.
2. Your eardrum vibrates with
sound waves
3. This causes 3 tiny bones
called the ossicles (the
hammer, anvil and the stirrup)
of your middle ear to vibrate
PROCESS OF HEARING
4. The vibrating stirrup pushes
against the oval window of the
cochlea in the inner ear. The
cochlea is fluid filled and waves are
created.
5. Inside the cochlea is a basilar
membrane with hair cells that are
bent by the vibrations and are
transduced into a neural impulse
SOUND WAVES REACH THE
In the middle ear, the sound waves hit
outer ear
EAR The
the eardrum and move the hammer,
collects sound
and funnels it
to the eardrum.
anvil, and stirrup in ways that amplify
the vibrations. The stirrup then sends
these vibrations to the oval window of
the cochlea.
In the inner ear,
waves of fluid
move from the
oval window over
the cochlea’s
“hair” receptor
cells. These cells
send signals
through the
auditory nerves to
the temporal lobe
of the brain.
PROCESS OF HEARING
6. Hair cells synapse with auditory
neuron whose axons form the
auditory nerve
7. The auditory nerve transmits sound
messages though your medulla,
pons and thalamus to the auditory
cortex of the temporal lobe.
 What cell is triggers neural impulses
in the eye?
INNER EAR AND VESTIBULAR SENSE
 The semicircular canals are
connected to the cochlea by the
vestibular sacs.
 The semicircular canals contain
substance that move when our
head rotates or tilts and allows us
to maintain our vestibular sense:
sense of our body movement and
position
THE MAN WHO LOST HIS BODY
https://www.youtube.com/watch?v=bGlZpZgwnAc
HOW DO WE PERCEIVE PITCH: 2 THEORIES
 Helmholtz’s Place Theory: argues we hear different
pitches because different sound waves trigger activity at
different places in the cochlea’s membrane…easily
explains high pitches since these pitches are highly
localized.
 Frequency Theory: We sense pitch by the basilar
membrane in cochlea vibrating at the same rate as the
sound. Explains low pitch well….
Volley Principle- alternate firing to get
over 1000 fires per sound
HOW DO WE LOCATE SOUNDS
Why is
Having 2
Ears
Important?
PARALLEL PROCESSING
Just like with vision, audition involves
parallel processing
Time difference
Intensity
memories
HEARING LOSS
 Conductive Hearing Loss:
hearing loss caused by damage
to the mechanical system that
conducts sound waves to the
cochlea like eardrum and
ossicles.
 Solution to Conductive Hearing
Loss?
Hearing aid
HEARING LOSS
Sensorineural
Hearing Loss:
damage caused to
cochlea’s receptor
cells (hair cells) or
auditory nerves.
Solution?

 Cochlear Implant
OLDER PEOPLE SUFFER MOST HEARING
LOSS WITH HIGH FREQUENCY SOUNDS

TOUCH
Premature Babies
Monkeys
Infant allowed to see, hear, smell (but not touch) become
desperately unhappy
 Skin sensations are a variation of the basic 4
 Pressure
 Warmth
 Cold
 Pain
SENSE #3: TOUCH
Pain Is a Good Thing!
Gate Control Theory:
theory that the spinal cord contains a
neurological “gate” that blocks pain signals
or allows them to pass on to the brain
“gate” opened by the activity of pain signals
traveling up small nerve fibers
“gate” closed by activity in larger fibers or by
information coming from the brain
SOCIAL INFLUENCE ON PAIN
-Pain is both a physiological
and a psychological
phenomenon.
-Depending on symptoms,
doctors may use drugs,
surgery, etc. or relaxation
training, thought distraction.
Example: Lamaze Method
https://www.youtube.com/watch?v=7ZRYiOa5lM8
MEMORIES OF PAIN
 More to our memories of pain than the pain we
experienced.
 People tend to overlook duration of pain and instead
concentrate on its peak moments and how much
pain they felt at the end.
 What do doctors do because of this?
Taper down procedures
GIRLS BORN WITHOUT PAIN RECEPTORS
https://www.youtube.com/watch?v=J2ECNZA60XE – 5 minute video
Ashlyn Blocker article
http://www.nytimes.com/2012/11/1
8/magazine/ashlyn-blocker-feelsno-pain.html?_r=2
SENSES 4 & 5: TASTE AND SMELL
 Why are Taste and Smell studied
together?
Why are taste &
smell studied
together?
TASTE
4 Basic Sensations
 Sweet
 Sour
 Salty
 Bitter
 200 taste buds
 Reproduce every 1 or 2 weeks
 Older= decrease in taste buds
 Smoking and Alcohol= decrease in taste buds
THE SURVIVAL FUNCTIONS OF BASIC
TASTES
Taste
Sweet
Salty
Sour
Bitter
Umami
Indicates
Energy source
Sodium essential to
physiological processes
Potentially toxic acid
Potential poisons
Proteins to grow and
repair tissue
TASTE AND SMELL
Taste and Smell are both
chemical senses.
Tongue is central muscle for
taste which contain taste
buds.
Smell runs through receptor
cells in nasal cavity which send
neural signals to the olfactory
bulbs in the brain.
SMELL
5 million receptor cells at the top of your nasal
cavity
Detect 10,000 odors
Decreases with age
Have your own chemical signature
SMELL
 Nasal Cavity brings the smell up to your receptors
 Receptor cells send the message to the brain’s olfactory
bulb
 Then to the temporal lobe’s primary smell cortex
 Parallel Processing
Olfactory
nerve
Olfactory
bulb
Nasal
passage
Receptor cells in
olfactory membrane
SMELL AND EMOTION
Sense of smell activates
areas in limbic system
involved in emotion and
memory.
Smells can often evoke
memories of the past or
emotional experiences
more often than most
other senses.
SENSORY RESTRICTION
People born without access to a sense,
compensate with development of
stronger other senses.
Sensory Restriction has produced mixed
results depending on context:
Early Experiments: disorientation,
hallucinations, etc.
SUMMARIZING THE SENSES
SENSORY SYSTEM
SOURCE
RECEPTORS
Vision
Light waves striking the eye
Rods and cones in the retina
Hearing
Sound waves striking the outer ear
Cochlear hair cells in the inner ear
Touch
Pressure, warmth, cold, pain on
skin
Skin receptors detect pressure,
warmth, cold, and pain
Taste
Chemical molecules in the mouth
Basic tongue receptors for sweet,
sour, salty, bitter, and umami
Smell
Chemical molecules breathed in
through the nose
Millions of receptors at top of nasal
cavity
Body Position – kinesthesia
Any change in position of a body
part, interacting with vision
Kinesthetic sensors all over the
body
Body Movement –
vestibular sense
Movement of fluids in the inner ear
caused by head/body movement
Hairlike receptors in the
semicircular canals and vestibular
sacs