Download Senses Other Than Vision Hearing (Audition) Transmission of

Senses Other Than Vision
Hearing
The Kinesthetic Senses
Touch
The Chemical Senses
Hearing (Audition)
• Sound begins as pressure waves in a
medium (usually air).
• The frequency of the pressure waves
corresponds to the pitch of the sound.
• The amplitude of the pressure waves
corresponds to the intensity of the sound.
• The particular mixture corresponds to the
timbre of the sound.
Transmission of Vibrations
Basilar membrane
• Pressure waves in the air vibrate the tympanic
membrane (ear drum),
• Which sets into motion the three bones or ossicles of the
middle ear,
• Which vibrates the oval window of the cochlea.
• Which drives the fluid within the cochlea, driving the
basilar membrane.
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The Cochlea and Pitch Perception
• The Cochlea resembles a snail shell.
• The shell gets wider as one moves along the
coils toward the inner end.
• Because of this shape, standing pressure waves
are created whose peaks depend on the
frequency of the vibrations – high frequency
near the oval window, low frequency near the
tip.
• The perceived pitch of the sound depends on
where along the basilar membrane the
vibrations are greatest.
The Cochlear Implant
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The bending of the basilar membrane stimulates hair cells, which in
turn affect the rate of firing of the associated auditory neurons.
If the hair cells are destroyed, deafness occurs.
Surgeons can correct this problem by inserting an electrode array
into the cochlea.
An electronic device stimulates different electrodes depending on
the sound frequencies entering a microphone, artificially stimul ating
the appropriate neurons.
The Kinesthetic Senses
• The kinesthetic senses
include:
– The vestibular senses (via the
semi-circular canals)
• A sense of down
• Senses of rotation (angular
acceleration): pitch, yaw, and
turn
– The proprioceptive senses
• Joint angle
• Muscle length and tension
• These allow us to know
where are various limbs are
and how the body is moving
through space.
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The Chemical Senses
• The chemical senses are so called
because they are based on the chemical
properties of the materials being sensed.
• Two senses fall into this category:
– Smell
– Taste
Smell
• Breathing in conveys odorant
molecules to the olfactory
bulb.
• There, olfactory receptors
recognize odorant molecules.
• Activated receptors affect the
firing of olfactory neurons .
• The brain interprets
combinations of neural
activity as particular smells.
Receptors for Smell
• At one time there was a theory around, based on
analysis of the way people categorize various
smells, that there might be perhaps seven smell
receptors. These were given names like “floral,”
“pungent,” and “putrid.”
• However, recent evidence from DNA studies
suggests that there may be as many as 100 to
1000 different smell receptor protiens.
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Organs of Taste
• Taste receptors are located in the “taste buds” of
the tongue.
• There are four kinds of taste receptors known
and now possibly a fifth.
The Primary Tastes
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Sweet
Sugars
Sour
Weak Acids
Salty
Salts
Bitter
Alkaloids
And maybe one more . . .
• Umami or “savory” Certain amino acids
“Taste” = Taste + Smell
• What we often call the “taste” of food is
actually the combination of its taste and
smell. You can check this for yourself:
– While holding your nose, try munching on:
• A raw potato
• A raw onion
– The two have a similar crunchy texture and
bland taste. With your nose held, you will
have trouble telling them apart!
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Touch
• “Touch” actually includes a number of
specific sensory qualities, including:
– Light pressure
– Deep pressure
– Hot
– Cold
• There are specialized receptors for each
of these qualities.
Aristotle’s Five Senses
• The ancient Greek philosopher Aristotle held
that there are five senses: Sight, hearing, touch,
taste, and smell. We are still taught in primary
school that there are only five senses.
• But old Aristotle missed some important ones,
including the kinesthetic senses and various
forms of pain. And if we classified each type of
sensory receptor as providing a different
“sense,” we would have to say that there are
hundreds, perhaps thousands of senses.
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