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 too

McGurk 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