Lecture 18 Flashcards
What is the stimulus for hearing?
Pressure waves
How are the waves of hearing created?
Through expansion and compression of the molecules in some conducting medium which we experience as sound
What are the two fundamental properties of sound waves?
Frequency and amplitude
What is Frequency?
Frequency refers to the number of cycles per second measures in hz
What is Frequency perceptually?
Frequency is related to the perceptual experience of pitch
What does Amplitude describe?
The amount of compression and expansion of molecules in conducting medium
What is Amplitude Perpetually?
The perceived loudness
How decibels work?
Absolute threshold is 0 and this value is measured on a logarithmic scale where each increase of 10 equated ti 10x increase in loudness
What is the auditory system designed to do?
Funnel in presssure waves and translate them into neural impulses
What does the outer ear do?
Funnels sound toward the eardrum (tympanic membrane) which vibrates in response to incoming waves
What 3 bones make up the
Middle ear?
Hammer (malleus)
Anvil (incus)
Stirrup (stapes)
What is the function of the middle ear?
Amplify the pressure waves relayed by the eardrum 30x
What is the function of a Hammer?
It is connected to the eardrum which forms the boundary between the out/middle ear
What is the function of the anvil?
Connects the two bones in the middle ear
What is the function of the Stirrup?
Is connected to the oval window which forms the boundary between the middle/inner ear
What is the Cochlea?
A fluid filled tube located in the inner ear
What is inside the Cochlea?
The organ of corti
What does the organ of corti do?
Rests on the basilar membrane and contains 16000 hair cells that act as sound receptors
How does the Basilar membrane work?
Vibrations from the oval window cause fluid in the cochlea to move which creates waves in the basilar membrane. The waves bend the hair cells causing them to fire action potentials. Then the hair cells synapse with the auditory nerves.
Where do impulses from the ear go?
Signals go to the thalamus and then to the primary auditory cortex
How does Amplitude affects sound waves?
High amplitude sound waves bend the hair cells more resulting in more neurotransmitter release, resulting in a higher rate of firing
How is loudness coded?
As a function of both the firing rate and identity of which neurons are firing
What does Frequency Theory suggest?
Nerve impulses match the frequency of sound wave being coded
What is one problem Frequency theory?
The absolute refractory period that limits the firing rate of a neuron
What is Place theory?
The specific place in the cochlea where a particular frequency of sound wave bends a hair cell most strongly will contribute to the coding of pitch
What are Low pitches coded in accordance with?
Frequency theory
What are the High pitches coded in accordance with?
Place theory
What does Binaural hearing assist with?
Localizing sound
How does Binaural hearing help with localizing sound?
The difference in arrival time of the sound to the different ears. Also the difference in intensity
What does Conduction deafness result from?
Problems relating to the mechanical conduction of sound to the cochlea
What can fix Conduction deafness?
Hearing aids
What does Nerve deafness result from?
Damage to the receptors or auditory nerve
What can cause Nerve deafness?
Chronic exposure to loud noise
What is Gustation?
taste
What does Gustation produced by?
Stimulation of taste buds
What does Chemical senses rely on?
Chemical molecules
What is Umami?
A fifth dimension that modulates our perception of the other 4
What does perception specific taste result from?
Particular mixtures of neural signals related to these basic dimension
What can taste preferences be related to?
Evolutionary selection pressures
