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Flashcards in Chemical Senses Deck (41):

What do small positively charged things taste like?



What 4 things encode taste or are important to taste?

Pattern of neural activation


Other perceptual elements like temperature



What are the two chemical senses and what type of receptors do they have?

gustation and olfaction have chemoreceptors


Give the hierarchy of structures in taste (ie different cell/structure types)

Taste bud
Taste cells


What are the components of a taste bud?

Microvilii project into the taste pore and then an orange like array of taste cells surrounds. Basal cells are at the end of the taste bud and provide support


Where are the four basic tastes tastable?

All over the tongue.


How can you only stimulate certain parts of the tongue with a taste?

By using very very low concentrations of it


Describe the papillae

Bathed in fluid, the papillae are covered in taste buds (hundreds per papillae, 2000-5000 a person). Each papillae has a taste that it is maximally sensitive to


How many taste buds are in people (n practice)

Range from 500 to 20000, though most say 2000-5000


How long does it take for taste cells to turnover?

Every two weeks


What are axons from taste cells called?

Gustatory afferent axons


Are taste cells capable of having action potentials? What type of potentials do they have?

They can produce action potentials after building up a large enough receptor potential


How many tastes can a taste cell detect?

Taste cells can detect 1 or more tastes, though usually more than one.


What are the sodium channels of salty taste receptor cells like?

They are not voltage gated and they are always open at rest. Depolarization from sodium influx causes calcium to enter the cell and cause neurotransmitter release in an action potential


What are sour taste cell receptor channels like? How do sour tastes give a double whammy depolarization?

Same as the salty sodium ones, except they let protons and high energy anions in. Protons can block potassium channels, preventing it form leaving the cell and causing an even greater depolarization


What three tastes use a G protein coupled receptor? What is the effector protein in these pathways called?

Sweet, bitter and umami have G protein coupled receptors.

The effector protein for these G proteins is called phospholipase C


What does phospholipase C do in gustation?

When it is activated by the G protein it makes IP3 which causes inflow of calcium from calcium stores/extracellular and inflow of extracellular sodium


Why can't bitter flavours be distinguished even though there are 30 different types of T2R receptors?

All 30 types exist on one taste cell, which sends one ambiguous action potential regardless of which receptor is activated


What two types of receptor proteins do sweet tastes activate?

T1R2 and T1R3


What type of receptors do umami tastes activate? (two)

T1R1 and T1R3


How many cranial nerves innervate the tongue? Which ones?


Facial nerve (front of tongue)
Laryngeal nerve (back of tongue)
Vagus nerve (Down to pharynx)


Where do the three cranial nerves of the tongue innvervate>

All converge onto gustatory nucleus in brainstem


Where do axons from the gustatory nucleus on the brainstem go? Where do they go from there?

To the thalamus, on the ventral posterior medial (VPM) nucleus, this part of the thalamus deals with sensory info from the head. From there the VPM taste neurons send axons to the primary gustatory cortex


Where is the primary gustatory cortex located?

On Brodmann's area 36 and the insula-operculum regions of the cortex, near the tactile representation of the tongue


Which two pathways flow out of taste system?

1 goes down into ventral brainstem for swallowing, vomiting and salivating

One is involved in conscous mediation of perception of taste


Is there decussation in taste pathways?



What gives the vast variety of tastes available to us?

The relative activation of tase cells


Where is the olfactory epithelium?

On the roof of the nasal cavity


What is the bone that seperates the oflactory epithelium from the olfactory bulb?

The cribiform plate


What three things are in the mucus layer of the olfactory epithelium?

Salts, sugars, enzymes and antibodies

The enzymes are to stop stimulation once odour has arrived


Why are dogs more sensitive to smell?

Greater number of olfactory receptor cells


What type of receptor is there on the olfactory receptor cell?

A G protein coupled receptor with the effector adenylyl cyclase (makes cAMP to open calcium channels)


What happens when a receptor is activated on a olfactory receptor cell?

The G protein is activated which then activates adnylyl cyclase. Adenylyl cyclase makes cAMP, which opens calcium channels. Inflow of calcium causes opening of chloride channels (to let it out). Letting chlorine out of the cell depolarizes it,


What part of the olfactory receptor cells do odours interact with?

The cilia on these cells


Are olfactory receptor cells exclusive to one smell?

No,they are selective but not exclusive to one smell.


What are the repeating units of the olfactory bulb?

The glomerulus, which connects olfactory receptor cells to second-order olfactory neurons.


What type of inputs do glomerulus have?

Similar types of cells from across olfactory epithelium going to same glomerulus results in a segregation of info.


What are the two pathways out of the olfactory bulb?

I goes to olfactory tubercle, which then relays axons to medial dorsal nucleus (in thalamus) to orbitofrontal cortex (conscious detection of odours)

The second goes to the olfactory cortex and temporal lobe. First goes to olfactory cortex without synapsing in the thalamus, and then the pitiform cortex under the brain (medial), which has a direct connectivity with olfactory and limbic system.


What causes the change in colour in colour sensitive dye?

The polarity of fluid molecules.


What makes each olfactory receptor cell different?

Each one has its own type of receptor cell protein, there can be repeats of these cells scattered through the epithelium, these respond to different odours differently


Temporal coding of smells

May give information about quality of the smell