Ear, Taste & Smell

7/27/2019 Ear, Taste & Smell

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Chapter 8

Special Senses


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The Ear

Houses two sensesHearing

Equilibrium (balance)

Receptors

Sound receptors

Mechanoreceptors Both stimulated by the movement of fluid


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Anatomy of the Ear

The ear is divided into three majorareas

Outer (external) earMiddle ear

Inner (internal) ear


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Outer (external) Ear

Involved inhearing only

Structures ofthe externalear

Pinna

(auricle)

Externalauditory canal


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The External Auditory Canal

Short, narrow chamber in the temporalbone of the skull

Lined with skin

Ceruminous (wax) glands are presentthat secrete earwax or cerumen

Sound waves entering the canaleventually hit the tympanic membraneor eardrum and cause it to vibrate

Canal ends at the eardrum, which

separates the outer from the middle ear


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The Middle Ear or Tympanic Cavity

Air-filled cavity within the temporal bone

Only involved in the sense of hearing

Pharyngotympanic (auditory) tube Runs obliquely downward to link the

middle ear cavity with the throat

Allows for equalizing pressure duringyawning or swallowing

Tube is otherwise collapsed


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Bones of the Tympanic Cavity

3 of the smallestbones in the bodyspan the cavity

(ossicles)

Malleus (hammer)

Incus (anvil)Stapes (stirrup)


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Bones of the Tympanic Cavity

Vibrations fromthe eardrum

moves themalleus

These 3 bonestransfer soundto the inner ear


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Inner Ear or Bony Labyrinth

A maze of bony chambers within thetemporal bone

Cochlea

Vestibule

Semicircularcanals


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Inner Ear or Bony Labyrinth

Includes sense organs for hearing &balance

Filled with perilymph


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Static Equilibrium Maculae receptors within the vestibule

Report on the position of the head withrespect to the pull of gravity when the bodyis not moving (static = rest)

Anatomy of the maculae

Hair cells are embedded in the otolithicmembrane

Otoliths (tiny stones) float in a gel around

the hair cellsMovements cause otoliths to bend the hair

cells sends impulses along the vestibularnerve to the cerebellum of the brain


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Function of Maculae


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Dynamic Equilibrium

Responds to angular or rotatory movements

of the head Crista ampullaris receptors found within the

semicircular canals

Tuft of hair cells are covered with agelatinous cap called the cupula


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Dynamic Equilibrium

During angular headmovements

The cupula stimulates thehair cells

An impulse is sent via thevestibular nerve to the

cerebellum


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Mechanism of Hearing

Organ of CortiLocated within the cochlea

Hearing receptors hair cells on the

basilar membraneGel-like tectorial membrane is capable of

bending hair cells

Cochlear nerve attached to hair cellstransmits nerve impulses to auditory cortexon temporal lobe


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Hearing- Anatomy of the Cochlea


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Mechanisms of Hearing

Vibrations from sound waves movetectorial membrane

Hair cells are bent by the membraneAn action potential starts in the

cochlear nerve

Continued stimulation can lead toadaptation


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Chemical Senses: Taste & Smell

Both senses use chemoreceptorsStimulated by chemicals in solution

5 types of taste receptors

Smell (olfactory) receptors

Sensitive to a much wider range of

chemicals Receptors for both senses complement

each other and respond to many of the

same stimuli


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Olfaction The Sense of Smell

Olfactory receptors are in the roof of

each nasal cavity

Neurons with long cilia (olfactory hairs)

Chemicals must be dissolved in mucus fordetection

Impulses are transmitted via theolfactory nerve

Interpretation of smells is made in theolfactory cortex of the brain


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Olfactory Epithelium


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The Sense of Taste Taste receptors

Taste buds (Widelyscattered throughoutthe oral cavity)

Location of tastebuds

Most are on thetongue

Soft palate

Inner surface ofthe cheeks


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The Tongue and Taste

The tongue is covered with 3 types ofprojections called papillae

Sharp or Filiform papillae no taste buds

Fungifiorm papillae rounded with tastebuds

Circumvallate papillae large papillae

with taste buds

Taste buds are found on the sides ofpapillae


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Structure of Taste Buds

Gustatory cells

Have gustatory hairs (long microvilli)

Hairs are stimulated by chemicalsdissolved in saliva and transmit impulsesto the brain


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Structure of Taste Buds

Impulses are carried to the gustatorycomplex by several cranial nerves

because taste buds are found indifferent areas

Facial nerve

Glossopharyngeal nerve

Vagus nerve


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Anatomy of Taste Buds


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Taste Sensations

Sweet receptorsSugarsSaccharineSome amino acids

Sour receptorsAcids

Bitter receptorsAlkaloids

Salty receptorsMetal ions

UmamiGlutamate- Beef taste of steak


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Chipped or broken teeth

Infection

And possibly death


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Girl who almost died from a brain

abscess following a tongue piercing

She had part of her skull removedto relieve pressure caused by the

infection

She can still feel the soft spotwhere the skull is missing

Rare, but real


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Blood loss

The tongue contains large blood vessels, and you're in

trouble if one of them is perforated. You could end up

having to have the vessel closed surgically in hospital.

There is also the possibility of hitting anddamaging a nerve

Imagine life with a tongue that doesn't work properly!

Lingering pain

Cases of neuralgia - severe, long-lasting nerve pain

Hepatitis or HIV

Unsterile instruments are a great way to spread

these and other infections


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Still not convinced?

If you must do this, be sure to go

to a reputable clinic, and be very

sure that they do things properly:

autoclave sterilization and gloves.

As we had tried to teach you with

tattooing, be a smart consumer!


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Developmental Aspects of theSpecial Senses

Slide 8.42Copyright 2003 Pearson Education, Inc. publishing as Benjamin Cummings

Formed early in embryonic development

Eyes are outgrowths of the brain

All special senses are functional at birth


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Normal slight severe ear infection
http://www.comdis.wisc.edu/facstaff/mrchial/images/OS5.GIFhttp://medicine.ucsd.edu/clinicalmed/ear-otoscope.jpghttp://www.kidshealth.org/parent/medical/ears/ear_infections.htmlhttp://www.kidshealth.org/parent/infections/ear/otitis_media.htmlhttp://www.kidshealth.org/parent/infections/ear/otitis_media.htmlhttp://www.kidshealth.org/parent/infections/ear/otitis_media.html


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How Are Ear Tubes Inserted?

Ear tubes are inserted through an outpatient surgical procedure called a myringotomy. Amyringotomy refers to an incision (a hole) in the ear drum or tympanic membrane. This is

most often done under a surgical microscope with a small scalpel (tiny knife), but it canalso be accomplished with a laser. If an ear tube is not inserted, the hole would heal andclose within a few days. To prevent this, an ear tube is placed in the hole to keep it openand allow air to reach the middle ear space (ventilation).

Ear Tube SurgeryA light general anesthetic (laughing gas) is administered for young children. Some olderchildren and adults may be able to tolerate the procedure without anesthetic. Amyringotomy is performed and the fluid behind the ear drum (in the middle ear space) issuctioned out. The ear tube is then placed in the hole. Ear drops may be administeredafter the ear tube is placed and may be necessary for a few days. The procedure usuallylasts less than 15 minutes and patients awaken quickly. Sometimes the otolaryngologist willrecommend removal of the adenoid tissue (lymph tissue located in the upper airwaybehind the nose) when ear tubes are placed. This is often considered when a repeat tubeinsertion is necessary. Current research indicates that removing adenoid tissue concurrentwith placement of ear tubes can reduce the risk of recurrent ear infection and the needfor repeat surgery.


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Vertigo-website

Tinnitus-website
http://www.thedoctorwillseeyounow.com/articles/behavior/vertigo_9http://www.ata.org/about_tinnitus/consumer/faq.htmlhttp://www.ata.org/about_tinnitus/consumer/faq.htmlhttp://www.ata.org/about_tinnitus/consumer/faq.htmlhttp://www.ata.org/about_tinnitus/consumer/faq.htmlhttp://www.thedoctorwillseeyounow.com/articles/behavior/vertigo_9http://www.thedoctorwillseeyounow.com/articles/behavior/vertigo_9http://www.thedoctorwillseeyounow.com/articles/behavior/vertigo_9


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Adaptation: decreasing sensitivity

Threshold: minimal amount of stimulusneeded to illicit a response.

Taste: Adapt: complete 1-5 minutes

Threshold: bitter lowest (poisons), sour, salt &sweet

Smell: Adapt: 50% after 1 sec.

Threshold: very low 1/25,000,000,000mg/ml.

Ear, Taste & Smell

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