hearing, touch, taste and smell
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Hearing, Touch, Taste and Smell
Hearing
Audition – the sense of hearing
Frequency of Sound Waves
• frequency - the number of the waves gives us the pitch if the sound.
Amplitude of Sound Waves
• amplitude - the height of the wave of the sound.
Absolute Threshold• Absolute Threshold =
zero decibels• 10 decibels = 10X
increase in sound intensity
• Example:– A 30 decibel sound is
_____ times louder than a 10 decibel sound
– A 40 decibel sound is _____ times louder than a 10 decibel sound
Parts of the Ear
Transduction• Overview – Eardrum, Hammer, Anvil, Stirrup, Oval Window,
Cochlea, Auditory Nerve, Temporal Lobe, Auditory Cortex
1. Outer Ear Ear Drum – tight membrane that vibrates with sound waves. Transmits sound to the bones of the middle ear.
2. Middle Ear hammer, anvil, stirrup to cochlea’s oval window
3. Inner Ear Cochlea – coiled fluid filled tube where transduction
occurs– Oval window’s vibrations cause basilar
membrane’s hair cells to turn vibrations into neural impulses
4. Auditory Nerve – send neural messages via the thalamus to the auditory cortex in the brain.
5. Thalamus to Temporal lobes Auditory cortex
It is all about the vibrations!!!
The structure of the ear
Bones of the middle ear = the hammer, anvil, stirrup which vibrate with the eardrum.
The structure of the ear
Mechanical vibrations triggered by sound waves are transduced into neural impulses by _____________?
_____________ do the same job for vision as __________ do for audition
Neural impulse to the brain
Perceiving Loudness• Damage to Basilar membrane’s hair
cells = hearing loss (lose sensation of soft sounds)– # of activated hair cells allows us to
perceive loudness– Compression – harder to hear sounds are more
amplified than loud sound
Pitch Theories
Place Theory and Frequency Theory
Place Theory or Herman von Helmholtz Theory
• Brain determines pitch by recognizing the place on the membrane that is generating the neural impulse
• Best explains how we sense high pitches
Frequency Theory• Brain knows pitch by the
frequency of the neural impulse– Frequency (speed) of sound wave
matches the speed of the neural impulse.
• Theory limitations: Can’t explain high pitch sounds (neural impulses can only travel at 1000 impulses per sec.)
• Best explains how we hear low pitches
• Example:
Volley Principle• Neural cells
alternate firing in rapid succession
• Can achieve a combined frequency of above 1000 waves/sec
Locating Sound• Sound waves strike
one ear sooner and more intensely in the direction of the sound
DeafnessConduction Deafness
• Damage to the mechanical system that conducts vibrations in the middle ear (hammer, anvil, stirrup).
• You can replace the bones or get a hearing aid to help.
• Example:
Nerve (sensorineural) Deafness
• The hair cells on the basilar membrain in the cochlea get damaged.
• Loud noises can cause this type of deafness.
• NO WAY to replace the hairs.
• Cochlea implant - converts sound waves to into electrical signals.
• Example:
Touch
• Receptors located in our skin.• Types of touch
–Pressure*–Warmth–Cold–Pain
• Sensation of hot
Kinesthetic Sense• Tells us where our
individual body parts are.
• Receptors located in our joints, tendons, bones and ears
• Example: Without the kinesthetic sense
you could not touch the button to make copies of your buttocks.
Vestibular Sense• Enables you to
sense your body position and balance
• Located in our semicircular canals in our ears.
• Example:
Pain• Biological Influences
– Noiceptors – sensory receptors that detect hurtful temperatures, pressure or chemicals
– Gate-control theory* – Endorphins– Phantom limb sensations– Tinnitus
• Psychological influences– Distraction– Memory of Pain – peak pain, end pain
• Socio Cultural Influences– More pain when others experience pain– Mirror neurons that empathize with others pain
Gate Control Theory• Gate Control Theory – spinal cord
contains a “gate” that blocks pain signals or allows them to pass through to the brain
• Example:
Taste
• Sweet, sour, salty and bitter–Umami
• Taste buds–Chemical sense
• Age and taste
Taste• Bumps on our tongue
are called papillae.• Taste buds are
located on the papillae 200+ each containing a pore.
• Pore – 50-100 taste receptor cells that sense food molecules
Sensory Interaction• Sensory interaction –
some senses influence others
• Examples:Jello in the shape of a brain looks so
unappetizing, it tastes terrible tooMcGurk Effect – seeing mouth
movements for ga, but hearing ha, we may perceive da
(saying one syllable, while hearing another, you perceive a third)
Smell• Olfaction
– Chemical sense– Olfactory receptors - odor molecules
fit into receptors like a lock and key located in the olfactory bulb
– Olfactory bulb – transmits smell from the nose to the brain
– Olfactory nerve – sends neural messages to from the olfactory bulb directly to the olfactory cortex in the brain bypassing the thalamus
– Olfactory cortex – receives information from the olfactory bulb
• Conscious awareness of odors• Identification of odors
– Hotline between olfactory cortex and limbic system (memory and emotion)
Smell (olfaction)
Smell and age
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