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 basilarmembrane•Basilar membrane inside cochlea (snailshaped structure, size of a pea)•Last of the 3 bones (the stapes or “stirrup” isresponsible for stimulating hair cells.
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 doesnt produce these echoes. (Site) Checklist for a Baby’s hearing.
Deafness•2 - 28 million deaf or hearingimpaired persons in U.S.•Most born with normal hearing•Deafness from loud noise, disease,or old age•Genetic factors contribute too.
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• Analyzed DNA• Work done on a “mutant” mouse• Protein mouse chromosome called “myosin” in mice equivalent to human chromosome
Synesthesia Steffie Tomson: Synesthesia Researcher . . . and Synesthete NOVAVideo 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
• 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 worksmay lead to treatment for the loss of smell(Anosmia) due to: Age Disease
Your Nose containsspecialized sensorynerve cells (neurons)with hairlike fiberscalled cilia on oneend.In the olfactory bulb,information organizedinto patterns that braininterprets as differentodors.
•VMN -- vomeronasal organ =special structure in the noseused 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 Channel Magic and the Brain