the auditory process. stimulus distal stimulus- in our environment produces a proximal stimulus ...

The Auditory Process The Auditory Process

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StimulusStimulus Distal Stimulus- in our Distal Stimulus- in our environment produces a environment produces a proximal stimulusproximal stimulus

Proximal Stimulus- form of Proximal Stimulus- form of sound waves reaching the sound waves reaching the earear

Sound waves are Sound waves are vibrations of molecules & vibrations of molecules & can be made by vibrating can be made by vibrating objects or air pushing past objects or air pushing past a chamber or by a sudden a chamber or by a sudden release of burst of air.release of burst of air.



Wavelengths vs. FrequencyWavelengths vs. Frequency WavelengthsWavelengths (frequency) is measured in cycles (frequency) is measured in cycles

per second or hertzper second or hertz FrequencyFrequency is another name for pitch is another name for pitch People can only hear a portion of the sounds People can only hear a portion of the sounds

out in nature, ranging from 20Hz to 20, 000 Hzout in nature, ranging from 20Hz to 20, 000 Hz AmplitudeAmplitude equals loudness and is measured in equals loudness and is measured in

decibelsdecibels Pitch equals timbrePitch equals timbre Most sounds are a mixture of frequenciesMost sounds are a mixture of frequencies The purest sound is one that has only one The purest sound is one that has only one

frequency vibrationfrequency vibration

Three sections of the earThree sections of the ear



Vibrations and the ear partsVibrations and the ear parts

Can be divided into three sectionsCan be divided into three sections External Ear: Depends on the vibration of External Ear: Depends on the vibration of

air moleculesair molecules Middle Ear: Depends on vibration of Middle Ear: Depends on vibration of

movable bonesmovable bones Inner ear: depends on waves in a fluid Inner ear: depends on waves in a fluid

which are converted into a stream of which are converted into a stream of neural signalsneural signals

External EarExternal Ear

Consists of the Consists of the PinnaPinna, the sound , the sound collecting cone.collecting cone.

Auditory canalAuditory canal which funnels the which funnels the message along to message along to the eardrumthe eardrum



Middle EarMiddle Ear Eardrum: membrane that Eardrum: membrane that

vibrates in response to the vibrates in response to the soundsound

Ossicles: made up of the Ossicles: made up of the hammer, anvil and stirruphammer, anvil and stirrup

Vibrations of the eardrum Vibrations of the eardrum are transmitted inward by are transmitted inward by a mechanical chain made a mechanical chain made up of the 3 smallest bones up of the 3 smallest bones in your body-the ossicles in your body-the ossicles which serve to amplify tiny which serve to amplify tiny changes in air pressurechanges in air pressure



Inner EarInner Ear Made of semicircular Made of semicircular

canals, which help you canals, which help you keep your balancekeep your balance

When your head moves When your head moves around and moves the around and moves the tiny hairs that line each tiny hairs that line each canal, it triggers the nerve canal, it triggers the nerve messages that are then messages that are then sent to your brain.sent to your brain.

Cochlea:Fluid filled, Cochlea:Fluid filled, coiled tunnel contains coiled tunnel contains receptors for hearing.receptors for hearing.



CochleaCochlea Within the cochlea is the basilar Within the cochlea is the basilar

membrane which holds the auditory membrane which holds the auditory receptorsreceptors

These receptors are called hair cells These receptors are called hair cells because they LOOK like little hairsbecause they LOOK like little hairs

Waves on the fluid of the inner ear Waves on the fluid of the inner ear stimulate the hair cells and convert the stimulate the hair cells and convert the message into neural impulses that are message into neural impulses that are sent to the brainsent to the brain

The signal is routed to the temporal lobeThe signal is routed to the temporal lobe

One of the theoriesOne of the theories Place TheoryPlace Theory (Herman von (Herman von

Helmholtz) Helmholtz) The perception of pitch is The perception of pitch is

determined by the vibrations of determined by the vibrations of different places (hair cells) along different places (hair cells) along the basilar membrane. (like a the basilar membrane. (like a guitar or harp)guitar or harp)

Different sets of hair cells are Different sets of hair cells are vibrated by different sound vibrated by different sound frequenciesfrequencies

The brain the detects the The brain the detects the frequency according to which frequency according to which area along the membrane is most area along the membrane is most activeactive



Theory # 2Theory # 2 Frequency Theory Frequency Theory

(Rutherford, 1886-)(Rutherford, 1886-) Perception of pitch Perception of pitch

corresponds to the rate corresponds to the rate at which the entire at which the entire basilar membrane basilar membrane vibrate (like a drum)vibrate (like a drum)

The brain detects tone The brain detects tone by the rate at which the by the rate at which the auditory nerve fiber fireauditory nerve fiber fire



Reconciling Place & Frequency Reconciling Place & Frequency TheoriesTheories

Both are validBoth are valid Hair cells are not independent, they vibrate together Hair cells are not independent, they vibrate together

(Frequency Theory)usually fire a(Frequency Theory)usually fire a The pattern of vibration travels as a wave along the The pattern of vibration travels as a wave along the

membranemembrane Wave peaks DEPEND on the frequency of the sound Wave peaks DEPEND on the frequency of the sound

wave (Place Theory). Neurons usually fire at about wave (Place Theory). Neurons usually fire at about 1000 impulses per second.1000 impulses per second.

Volley Principle: groups of auditory nerve fibers fire Volley Principle: groups of auditory nerve fibers fire neural impulses in rapid succession, creating volleys neural impulses in rapid succession, creating volleys of impulsesof impulses

# of impulses (see notes)# of impulses (see notes)

Taste- Gustatory SystemTaste- Gustatory System

Physical Stimuli-Physical Stimuli-chemical substanceschemical substances

Receptor cells and salivaReceptor cells and saliva Life SpanLife Span 4 primary taste: sweet, 4 primary taste: sweet,

sour, bitter and saltysour, bitter and salty Most respond to more Most respond to more

than one tastethan one taste Complex patterns of Complex patterns of

neural activityneural activity



Cultural Influence vs GeneticCultural Influence vs Genetic

Taste preferences are Taste preferences are largely learnedlargely learned

Density of taste budsDensity of taste buds Supertasters -4XSupertasters -4X Evolutionary reasonEvolutionary reason Ability to identify Ability to identify

flavors declines w/out flavors declines w/out odor cuesodor cues





Olfactory SystemOlfactory System

Olfactory ciliaOlfactory cilia Life span (30-60)Life span (30-60) Synapse in the Synapse in the

olfactory bulbsolfactory bulbs Only sense not routed Only sense not routed

through the thalamusthrough the thalamus No primary odorsNo primary odors Distinguish 10,000 Distinguish 10,000

odors but can’t nameodors but can’t name Female betterFemale better



Sense of TouchSense of Touch





the auditory process. stimulus distal stimulus- in our environment produces a proximal stimulus ...

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