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The five primary tastes
salty; taste of NaCl (table salt) in water
Acid; measures concentration of H+ ions
Umami; Japanese for "tasty" or "meaty:, as in protein rich foods such as sushi.
Taste receptors found on
lips, tongue, palate
Receptors for things we "want"
tend to be closer to the front of the tongue
Receptors for things we don't want tend to be
closer to the back of the tongue
Filiform papillae, which look
little threads, cover most of the tongue surface. These are non taste buds
Several gustatory receptor cells and supporting cells are
clustered in each taste bud.
*Individual taste buds cover entire surface of tongue
Three groups of taste buds on tongue
Fungiform papillae; little mushrooms
Foliate papillae; leaf-shaped, found along lateral surface of the posterior tongue.
Vallate papillae; form a V shaped row along the posterior tongue. Usually 7-10 of these
Gustatory Pathways to Brain:
3 cranial nerves carry taste sensations
facial (CN VII): anterior 2/3 of tongue
glossopharyngeal (CNIX): posterior 1/3
vagus (CN X): tonsils, palate, oropharynx
Primary gustatory cortex is in "mouth area" of postcentral gyrus
These three nerve branches combine to form a bundle of axons called the
The chorda tympani carries information to the
The sense of hearing depends on
the ear receiving pressure waves of air
Pressure waves of air are the relevant
stimulus for the auditory system
Pressure waves of air arrive at the ______, the external part of the ear, and are carried through the ______ ______ _____ to press against the _______ ________. The tympanic membrane vibrates as pressure waves of air push against it.
auricle; external auditory canal; tympanic membrane
Bone of the Ear
Inner ear structures:
Semicircular canals (balance)
*has 2 1/2 turns
- *Two fluid-filled chambers
- -Scala tympani
- -Scala vestibuli
*Between these chambers: spiral organ
Spiral organ is where auditory __________ occurs
*Auditory receptors (hair cells) sit on basilar membrane
*Rows of 3 outer hair cells and one inner hair cell
*Hairs (modified cilia) embedded in tectorial membrane
- *Hair cells synapse onto 1" afferents
- -cell bodies in spiral ganglion
- -axons form cochlear branch of CN VIII
The hair cells are small and don't send their information far. They make contact on a 1 degree afferent fiber with a cell body in the ______ ______ and axons that travel in the _______ branch of the __________ nerve.
spiral ganglion; cochlear; vestibulocochlear (CN VIII)
2 accessory structures are associated with the ear:
Ceruminous glands produce the
waxy substance found within the ear. Cerumen helps trap dirt and insects, and can even produce a protective earplug if the ear is exposed to loud noises.
Auditory tube is a
tube that connects the middle ear to the nasopharynx. This equalizes the pressure on both sides of the tympanic membrane unless the tube becomes swollen or clogged with mucus.
The Sound Conduction Pathway:
1. Waves of air arrive in external auditory canal.
2. Air moves tympanic membrane
3. Tympanic membrane moves ossicles
4. Stapes moves oval window
5. Oval window moves perilumph fluid in scala vestibuli
The Sound Conduction Pathway:
6. Waves of fluid in scala vestibuli set up vibrations in basilar membrane, which moves hair cells
7. Fluid can pass from scala vestibuli to scala tympani at helicotrma
8. Fluid in scala tympani
9. Round window is outlet for pressure