hearing. sound sound is vibrations of molecules amplitude, wavelength, and purity affect qualities...
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HEARING
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SOUND• Sound is vibrations of molecules• Amplitude, wavelength, and purity affect qualities of loudness,
pitch, and timbre
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HUMAN HEARING CAPACITIES• Frequency (wavelength): measured in cycles per second, hertz
(Hz)• Higher frequency creates higher pitch• Humans hear btwn 20 Hz and 20,000 Hz
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HUMAN HEARING CAPACITIES• Amplitude affects loudness• Measured in decibels (dB)• Perceived sound doubles every 10 dB• Loudness requires an interaction of frequency and amplitude
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HUMAN HEARING CAPACITIES• Purest sound has only a single frequency of vibration• Most sounds are mixed
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SENSORY PROCESSING IN THE EAR• External ear depends on vibrations of molecules• Consists of the pinna• Pinna collects sound and funnels it down the auditory canal to
the eardrum
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SENSORY PROCESSING IN THE EAR• Middle ear consists of the hammer, anvil, and stirrup• Hammer, anvil, and stirrup are called ossicles• Ossicles amplify changes in air pressure
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SENSORY PROCESSING IN THE EAR• Inner ear consists of the cochlea: fluid filled, coiled tunnel that
contains receptors for hearing• Sound enters through the oval window• Ear’s neural tissue lies in the cochlea; it sits on the basilar
membrane: runs the length of the cochlea, holds auditory receptors
• Auditory receptors are called hair cells• Waves in fluids in the inner ear stimulate the hair cells, which
convert the motion into neural impulses• Impulses travel to the thalamus, then to the auditory cortex
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AUDITORY PERCEPTION: PLACE THEORY• Holds that perception of pitch corresponds to the vibration of
different portions, or places, along the basilar membrane• Frequency is detected by specific regions of the basilar
membrane
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AUDITORY PERCEPTION: FREQUENCY THEORY• Holds that perception of pitch corresponds to the rate, or
frequency, at which the entire basilar membrane vibrates• Ex: 3000 Hz would cause the membrane to vibrate 3000 times
per second
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RECONCILING PLACE AND FREQUENCY THEORIES• Both are valid but both have flaws• Volley Principle: holds that groups of auditory nerve fibers fire
neural impulses in rapid succession, creating volleys of impulses
• Improves frequency theory
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PERCEIVING SOURCES OF SOUND• Auditory localization: locating the source of a sound• 2 cues: intensity and timing of arrival at each ear
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OUR CHEMICAL SENSES: TASTE AND SMELL
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TASTE: THE GUSTATORY SYSTEM• Physical stimuli for taste are based on chemical substances
that are soluble• Taste buds are clusters of taste cells• Taste buds absorb chemical dissolved in saliva, which trigger
neural impulses
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PRIMARY TASTES• Sweet, sour, bitter, and salty• Some preferences are innate, some are learned• Sensitivity to certain tastes depend on density of taste buds• Women more likely to be supertasters than men
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SMELL: THE OLFACTORY SYSTEM• Olfactory cilia are tiny hairlike structures located in the upper
portion of the nasal passages• These receptors have axons that synapse directly with cells in
the olfactory bulb at the base of the brain• Only sense not routed through the thalamus
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SMELL• Humans can distinguish about 10,000 different odors• Identifying odors can be difficult• Females tend to be more accurate with identifying odor
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SENSE OF TOUCH
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FEELING PRESSURE• Skin has receptive fields where CNS cells are most sensitive• Nerves route through the spinal cord to the brainstem• Then project through the thalamus and onto the
somatosensory cortex in the parietal lobe• Some cells in the somatosensory cortex respond to specific
features of touch
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FEELING HOT AND COLD• Skin has warm and cold receptor nerves• When warmth is applied the warm receptors fire rapidly and
cold receptors cease and vice versa for when cold is applied
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FEELING PAIN• Pain travels to the brain through 2 pathways• Fast pathway registers localized pain---sharp pain---depend on
myelinated neurons called A-delta fibers• Slow pathway conveys longer-lasting, aching, or burning
pain---depends on unmyelinated neurons called C fibers
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PAIN PERCEPTION• Very subjective• Pain can be blocked• Gate-control theory: holds that incoming pain sensations must
pass through a “gate” in the spinal cord that can be closed, thus blocking ascending pain signals
• Studies suggest that the release of endorphins creates the analgesic effect
• Discovery of a descending neural pathway that originates from the periaqueductal gray (PAG) in the midbrain; endorphins initiate activity in the PAG
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OTHER SENSES
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KINESTHETIC SYSTEM• Monitors the positions of the various parts of the body• Some receptors are in the joints---indicate bending• Others reside in the muscles---register tautness, or extension
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VESTIBULAR SYSTEM• Responds to gravity and keeps you informed of your body’s
location in space• Provides sense of balance (equilibrium)• Located in the inner ear• Semicircular canals make up largest part