Chemical senses Flashcards

Terms Definitions
Olfactory disturbances can be subdivided into how many groups?
Olfactory cells turn over every _____days
Gustatory cells turn over every ____days
olfactory cells
Neurons responsible for smell

Line the olfactory epithelium in the rear of the nasal air passages.

In mammals, each olfactory cell has cilia (threadlike dendrites) that extend from the cell body into the mucous surface of the nasal passages. Olfactory receptors are located on the cilia
Sides of the tongue tastes
Salty and sour
What is the name of CN 7?
With what mood disorder might dysosmia or parosmia be associated?
Depressive illness

Describe the mechanism by which the five kinds of taste receptors work.
See study guide.
Salty taste channels
Specialized Na+ selective Channel. Non voltage gatedBlocked by amiloride
What are the two chemical senses?
Gustation and Olfaction
What quality of taste does the back of the mouth detect?
Which cranial nerve innervates the posterior third of the tongue?
IX; glossopharyngeal nerve
vomeronasal organ
Set of receptors located near, but separate from, the olfactory receptors
Info. from the _________part of the tongue sends info. through which CN?
posterior, CN 9
What are the five basic tastes?
Saltiness, sourness, sweetness, bitterness, and umami
Sour taste
Sour = acidity = low pH = high concentration of H+ ions. Protons = Tastant
What qualities of taste does the tip of the tongue detect?
Sweet and Salty
If the anosmia or hyposmia is bilateral, what might the patient complain of?
Ageusia (loss of taste)
What does a basal cell do?
These create new receptor cells.

Describe the pathway taken by taste information in the brain.
When an olfactory receptor is stimulated, its axon carries an impulse to the olfactory bulb. The olfactory bulb sends axons to the olfactory area of the cerebral cortex, where neurons responding to a particular kind of smell cluster together. From the cortex, info connects to other areas that control feeding and reproduction.
Where are the vallate papillae located?
Near the back of the tongue

Explain how you would prove the existence of the five kinds of taste receptors.
1. Sweet
2. Sour
3. Salty
4. Bitter
5. Umami (Glutamate)

Use cross-adaptation.
How do the receptor cells on the olfactory cilia get stimulted?
Odorous molecules dissolve in mucus
How do we perceive the countless flavors of different foods?
Each food activates a different combination of the basic tastes, most foods have a distinct flavor as a result of their taste and smell, and other sensory modalities contribute to a unique food-tasting experience (texture and temperature)

Compare the VNO of adult humans with that of other mammals.
The vomeronasal organ (VNO) is a set of receptors located near, but separate, from the olfactory receptors. VNO receptors are specialized to respond only to pheromones, which are chemicals released by an animal that affect the behavior of other members of the same species, especially sexually. Although the VNO is reasonably prominent in most mammals and easy to find in a human fetus, in adults humans it is tiny and has no receptors. It seems to be vestigial—that is, a leftover from our evolutionary past. Humans nevertheless do respond to pheromones. Researchers have found at least one pheromone receptor in humans. Its structure resembles that of other mammals’ pheromone receptors, but for us, it is located in the olfactory mucosa along with normal olfactory receptors—not in the VNO.
How is the central pathway for smell different from all other sensory pathways?
Central pathways for smell differ in that they don't have to \"check-in\" at the thalamus.
Back of tongue tastes
The general lack of olfaction
Where are the BORN located?
Olfactory mucosa
Fatigue of receptors sensitive to source tastes
Olfactory glomeruli
~2000 on each bulbSpecific mappingEach glomerus receives input from a large region of the olfactory epitheliumreceives input only from receptor cells expressing a particular odorant receptor gene
Families of Taste receptor Genes
T1r and T2R
Gustatory information is transmitted through which cranial nerves?
7, 9, 10
What is the name of CN 10?
Structure on the surface of the tongue
Individual receptor cells are
Diverse -Different receptor cells respond differently to the same stimulus.Broadly tuned-Receptor cells respond to more than one type of stimulus (eg. both salty and sour)
Info. from the _________ and _________ is carried by which CN?
palate, epiglottis, 10
\"Labeled line\" coding
Specific neurons code for specific tastes, all the way up to the cerebral cortex (different receptors for each taste)
Which cranial nerve innervates the anterior two-thirds of the tongue?
VII; facial nerve
Taste receptor cells
~50-150 per taste bud. Varying response profiles even within a single taste bud
Axons of the mitral cells travel to the rest of the brain through what?
Olfactory tract
Define olfactory maps
Specific neurons in a specific place in the bulb respond to particular odors. The smell of a particular chemical is converted into a specific map within the neural space of the bulbs. The form of the map depends on the nature and concentration of the odorant.
Stimulus= High external salt concentration such as chicken soup. What happens in the taste receptor pathway?
1) Na+ enters through amiloride channels(inward current).2) Depolarization Amplified by voltage gated Na+ channels (receptor potential, no action potential)3) Ca2+ enters through Ca2+ voltage gated channels4)Synaptic vesicle fusion/ Transmitter release
What are the 4 qualities of taste?
Bitterness, sourness, sweetness, saltinessAcronym: BSSS
Where is the olfactory epithelium?
High up in the nasal cavity.

Distinguish between the labeled-line and across-fiber pattern principles.
In a system relying on the labeled-line principle, each receptor would respond to a limited range of stimuli and send a direct line to the brain.

In a system relying on the across-fiber pattern principle, each receptor responds to a wider range of stimuli and contributes to the perception of each of them. In other words, a given response by a given sensory axon means little unless the brain knows what the other axons are doing at the same time.
About 10,000 tastebuds exist in what four areas of the mouth?
Tongue, Palate, Pharynx, and Larynx
Where are the fungiform papillae located?
These are scattered throughout the majority of the tongue, starting at the most ventral part.
Complex flavors such as Banana are coded by
Patterns of activation across the population of receptors
Info. from the __________ part of the tongue travels through the ____________, which is branch of which cranial nerve?
anterior, chorda tympani, CN 7
Pathway Taste travels from tongue to brain
Tongue -> Medula -> Thalmus -> CortexTongue -> gustatory nucleus -> VPM -> Gustatory nucleus
What is the first relay station in the gustatory pathway?
Nucleus of the solitary tract (in medulla)
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