HEARING
SOUND
• Sound is vibrations of molecules
• Amplitude, wavelength, and purity affect qualities of loudness,
pitch, and timbre
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
HUMAN HEARING CAPACITIES
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Amplitude affects loudness
Measured in decibels (dB)
Perceived sound doubles every 10 dB
Loudness requires an interaction of frequency and amplitude
HUMAN HEARING CAPACITIES
• Purest sound has only a single frequency of vibration
• Most sounds are mixed
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
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
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
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
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
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
PERCEIVING SOURCES OF
SOUND
• Auditory localization: locating the source of a sound
• 2 cues: intensity and timing of arrival at each ear
OUR CHEMICAL
SENSES: TASTE AND
SMELL
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
PRIMARY TASTES
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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
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
SMELL
• Humans can distinguish about 10,000 different odors
• Identifying odors can be difficult
• Females tend to be more accurate with identifying odor
SENSE OF TOUCH
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
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
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
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
OTHER SENSES
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
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