Hearing Also known as Audition

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HearingAlso known as Audition
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The Stimulus Input Sound Waves

• Sound waves are composed of compression and
  expansion of air molecules.

Acoustical transduction Conversion of sound
waves into neural impulses in the hairs cells of
the inner ear.
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Sound Characteristics

1. Frequency (pitch)
2. Intensity (loudness)

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Hearing The Auditory System

• 1. Stimulus sound waves (vibrations of
  molecules traveling in air)
• 2. The amplitude refers to the height and
  subsequent intensity of the sound wave.
• 3. Loudness refers to the perception of the
  sound wave
• 4.Wavelength (pitch)
• -measured in cycles per second (Hz)

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• 5. Frequency refers to the number of compressions
  per second and is measured in hertz.
• High frequency high pitch
• 6. Sound pressure decibels

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Prolonged exposure above 85db?hearing loss
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Frequency (Pitch)

• Frequency (pitch) Dimension of frequency
  determined by wavelength of sound.
• Wavelength The distance from the peak of one
  wave to the peak of the next.

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Intensity (Loudness)

• Intensity (Loudness) Amount of energy in a wave
  determined by amplitude relates to perceived
  loudness.

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Anatomy of the Ear

• The ear is divided into three major areas
• Outer (external) ear
• Middle ear
• Inner (internal) ear

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The Ear
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• 1. The outer ear includes the pinna and is
  responsible for
• Altering the reflection of sound waves into the
  middle ear from the outer ear.
• Helping to locate the source of a sound.

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• 2. The middle ear contains the tympanic membrane
  which vibrates when struck by sound waves.
• Three tiny bones (malleus, incus, stapes) also
  hammer, anvil, stirrup (ossicles)
• transmit information to the oval window

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Parts of the Inner Ear

• Cochlea
• Oval window
• Semicircular canals
• Basilar membrane

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• 1. inner ear contains a snail shaped structure
  called the cochlea which contains fluid
• 2. hair cells are auditory receptors that excite
  the cells of the auditory nerve when moved by
  vibrations in the fluid of the cochlea.
• 3. lie between the basilar membrane and the
  cochlea.

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Cochlea

• Coiled, bony, fluid-filled tube in the inner ear
  that transduces sound vibrations to auditory
  signals.

Vibrating air?ossicles?fluid waves?electrical
impulses to the brain!
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Pitch perception explained in two theories
Place Theory suggests that sound frequencies
stimulate basilar membrane at specific places
resulting in perceived pitch.
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Theories of Audition

• Frequency Theory states that the rate of nerve
  impulses traveling up the auditory nerve matches
  the frequency of a tone, thus enabling us to
  sense its pitch.

Auditory Nerve Action Potentials
Sound Frequency
100 Hz
200 Hz
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• The current pitch theory combines modified
  versions of both the place theory and frequency
  theory
• Low frequency sounds best explained by the
  frequency theory.
• High frequency sounds best explained by place
  theory.

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• Volley principle states that the auditory nerve
  can have volleys of impulses (up to 4000 per
  second) even though no individual axon approaches
  that frequency by itself.
• provides justification for both theories

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• About 99 of hearing impaired people have at
  least some response to loud noises.
• Two categories of hearing impairment include
• Conductive or middle ear deafness.
• Nerve deafness.

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• Conductive deafness occurs if bones of the middle
  ear fail to transmit sound waves properly to the
  cochlea.
• Caused by disease, infections
• Can be corrected by surgery or hearing aids that
  amplify the stimulus.

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• Sensorineural deafness results from damage to the
  cochlea, the hair cells or the auditory nerve.
• Can be confined to one part of the cochlea.
• people can hear only certain frequencies.
• Can be inherited or caused by prenatal problems
  or early childhood disorders (rubella, syphilis,
  inadequate oxygen to the brain during birth,
  repeated exposure to loud noises, etc).

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• Tinnitus is a frequent or constant ringing in the
  ears.
• experienced by many people with nerve deafness.
• Sometimes occurs after damage to the cochlea.
• Similar to the mechanisms of phantom limb.

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Deaf Culture

• Cochlear implants are electronic devices that
  enable the brain to hear sounds.

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Cochlear Implant
Deaf Musician
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Other Important SensesModule 15
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• Other Important Senses
• Touch
• Taste
• Smell
• Body Position and Movement

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Other Important Senses

• Sense of touch is a mix of four distinct skin
  senses- pressure, warmth, cold, and pain.

Bruce Ayers/ Stone/ Getty Images
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Skin Senses

• Only pressure has identifiable receptors, all
  other skin sensations are variations of
  pressures, warmth, cold and pain.

Pressure
Vibration
Vibration
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Burning hot
Cold, warmth and pain
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Pain

• Pain tells the body that something has gone
  wrong. Usually pain results from damage to the
  skin and other tissues. There is a rare disease
  in which the person feels no pain.

Congenital Insensitivity to Pain with Anhidrosis,
or CIPA
Ashley Blocker (right) feels neither pain nor
extreme hot or cold.
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• Pain depends on several types of axons, several
  neurotransmitters, and several brain areas.
• Mild pain triggers the release of glutamate while
  stronger pain triggers the release of glutamate
  and substance P.
• Substance P results in increased intensity of
  pain.
• Morphine and opiates block pain by blocking these
  neurotransmitters.

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Gate-Control Theory
Melzak and Wall (1965, 1983) proposed that our
spinal cord contains neurological gates that
either block pain or allow it to be sensed.
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The Chemical Senses Taste

• Taste (gustation)
• Physical stimulus soluble chemical substances
• Receptor cells found in taste buds
• Pathway taste buds ?neural impulse ? thalamus ?
  cortex
• Taste learned and social processes

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Taste
Traditionally taste sensations consisted of
sweet, salty, sour and bitter tastes. Recently
receptors for a fifth taste have been discovered
called Umami.
Sweet
Sour
Salty
Bitter
Umami (Fresh Chicken)
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The Sense of Taste

• Taste receptors ? Taste buds (Widely scattered
  throughout the oral cavity)
• Location of taste buds
• Most are on the tongue
• Soft palate
• Inner surface of the cheeks

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Sensory Interaction

• When one sense affects another sense sensory
  interaction takes place.
• So the taste of strawberry interacts with its
  smell and its texture on the tongue to produce
  flavor.

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Smell
Like taste smell is a chemical sense. Odorants
enter the nasal cavity to stimulate 5 millions
receptors to sense smell. Unlike taste there are
many different forms of smells.
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Smell and Memories
Brain region (red) for smell is closely connected
with brain regions (limbic system) involved with
memory, that is why strong memories are made
through the sense of smell.
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Body Position and Movement

• The sense of our body parts position and
  movement is called kinesthesis.
• vestibular sense monitors the head (and bodys)
  position.

Wire Walk
Whirling Dervishes