HEARING

A Frog’s Ear

Human Ear

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.

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.

The Human Ear or Can you ear me?

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.

• 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

• 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

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.

Deafness

•Most born with normal hearing

•Deafness from loud noise, disease,

or old age

•Genetic factors contribute too.

•2 - 28 million deaf or hearing impaired persons in U.S.

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

• 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

• One Deafness Gene discovered in 1995

• Work done on a “mutant” mouse

• Analyzed DNA

• Protein mouse chromosome called “myosin” in

mice equivalent to human chromosome

Synesthesia

Steffie Tomson:

Synesthesia Researcher

. . . and Synesthete NOVA

Video Pre-Test for Synesthesia

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

Smell

• Learning how the process of smelling works may lead to treatment for the loss of smell (Anosmia) due to: Age Disease

• Olfactory neurons die and are replaced by new, identical ones.

• *Olfactory neurons are the only ones to do this (replace themselves every 28 Days)

In the olfactory bulb, information organized into patterns that brain interprets as different odors.

Your Nose contains specialized sensory nerve cells (neurons) with hairlike fibers called cilia on one end.

•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.

How does scent effect our experiences???

The Science of Sex Appeal... or what do we

see and smell about sexual attraction?

Discovery ChannelMagic and the Brain