The document summarizes key aspects of hearing and the ear. It discusses: - How hair cells in the cochlea detect sound waves and transmit electrical signals to the brain. - The basilar membrane contains thousands of hair cell bundles that are very sensitive and fast, responding up to 20,000 times per second. - The auditory system is over 1000 times faster than the visual system. Hair cells transmit signals to the auditory nerve. - Deafness can be conductive, sensorineural, or genetic. Over 50% of deafness in newborns is genetic. A gene for deafness was discovered in 1995.

1. HEARING

2. A Frog’s Ear

3. Human Ear

4. Hearing: Signals from a Hair Cell
• Hair Cells (cilia) play a vital role in
hearing.
• Cilia quiver with mechanical vibration of
sound waves.
• Cells produces brief electrical signals that
go to brain as acoustic information.

5. Hair cell bundles
•In 4 long parallel columns on basilar
membrane
•Basilar membrane inside cochlea (snail
shaped structure, size of a pea)
•Last of the 3 bones (the stapes or “stirrup” is
responsible for stimulating hair cells.

6. The Human Ear or Can you ear me?

7. Sensitivity and Speed of the Ear
• @16,000 hair cells in human cochlea
• 100-125 million photoreceptors in the eye
• Hair cells more sensitive and faster
than the eye receptors.

8. • Hair cells
 can’t be studied easily
 die quickly when taken from lab animals
 Good experiment lasts only 15 minutes
 taken from bullfrogs and mice to be studied
• Microelectrodes used to stimulate and study
hair cells

9. • Hair cells (cilia) operate like a light
switch…..
• From shortest to tallest when pushed
“on”… opposite for “off”
• Human cilia can turn on & off 20,000
times per second
• Bats -Whales have frequencies as high as
200,000 times per second

10. Auditory system is 1000 times faster than the
visual system
Hair cells in cochlea
• Hair cells in cochlea are connected to the
auditory nerve.
Ears not only receive sound but emit them as well.
A healthy ear emits soft sounds in response to the
sounds that travel into it. Detectable with sensitive
microphones, these otoacoustic emissions help
doctors test newborns' hearing. A deaf ear doesn't
produce these echoes. (Site)
Checklist for a Baby’s hearing.

12. Deafness
•2 - 28 million deaf or hearing
impaired persons in U.S.
•Most born with normal hearing
•Deafness from loud noise, disease,
or old age
•Genetic factors contribute too.

13. Types of Deafness
• Conductive = damage to middle ear
• Sensorineural = damage to inner
ear… (a) people don’t hear certain
frequencies (b) neurons in cochlea
damaged

14. • 1 out of every 1000 newborns
born “profoundly deaf”
• 1 out of 20 has significant hearing
loss
• Deafness associated with over 100
genetic disorders
• More than 50% of the time deafness
in newborn children is genetic

15. • One Deafness Gene discovered in 1995
• Analyzed DNA
• Work done on a “mutant” mouse
• Protein mouse chromosome called “myosin” in
mice equivalent to human chromosome

16. Synesthesia
Steffie
Tomson:
Synesthesia
Researcher
. . . and
Synesthete
NOVA
Video Pre-Test for Synesthesia

17. Smell and the Olfactory System
• Olfactory System can
distinguish thousands of odors
• The sense of SMELL is the Oldest and
most vital part of the brain.
• Primary mode of communication for most
animals
• Influences reproduction and taste for
animals

18. Smell

19. • Olfactory neurons die and are replaced
by new, identical ones.
• *Olfactory neurons are the only ones to
do this (replace themselves every 28
Days)
• Learning how the process of smelling works
may lead to treatment for the loss of smell
(Anosmia) due to: Age Disease

20. Your Nose contains
specialized sensory
nerve cells (neurons)
with hairlike fibers
called cilia on one
end.
In the olfactory bulb,
information organized
into patterns that brain
interprets as different
odors.

21. •VMN -- vomeronasal organ =
special structure in the nose
used for:
•Detecting phermones
•Receptors in nose are
thought to help detect
special chemical signals
called pheromones
•Phermones effect -
mating and
social functions in animals
and humans.

22. How does scent effect our
experiences???
The Science of Sex Appeal... or
what do we see and smell
about sexual attraction?
Discovery Channel
Magic and the Brain