EXP3202c Exam 3 Taste

How many genes for bitter receptors are there and what does that tell us?

25 bitter receptors on 3 different chromosomes. Tells us that DIFFERENT GENETIC MAKE-UP means that you and I might have different bitter experiences.

Bitter: usually means poisonous, but what is an example of a built-in system that helps us eat bitter things even though they don't taste great?

A compound (AMP) inhibits some bitter sensations and is naturally present in mother's milk.

What is flavor? How does the brain differentiate between tasting or smelling something?

A metasensation created by the brain's combination of smell and taste. Brain knows that something is in your mouth. Brain knows where odorant is coming from.

What are adaptation and cross-adaptation? What did the essay on water tastes teach you?

Adaptation: Loss of taste with constant stimulation. Why saliva doesn't taste salty. Essay teaches us that taste is subjective. What we taste now is what we were just tasting.

Know the disorders of taste we discussed. Also know the terms ageusia, hypogeusia and dysgeusia. Why can altered taste perception be so bad for overall health?

Aguesia: Total loss of taste. Hypoguesia: Decrease in taste of all or specific primaries/tastants Dysguesia: Distorted taste Xerostamia: Drymouth due to dysfunction of salivatory glands. Burning Mouth: Burning pain, usually affecting tongue, hard palate, and lips. Phantaguesia: Lingering, often unpleasant taste with nothing in the mouth. Initiated by strong tastes (coffee, garlic) Early satiety: Feeling full before eating adequate calories.

What brain regions (in order) get info about taste?

Cranial Nerves -> Medulla and pons > Thalamus > EITHER Dosomedial nucleus (Hedonic nature of taste OR Ventroposterior nucleus (projects to primary taste cortex in insula)

Know the names of the different types of papillae

Fungiform: TASTE. Mushroom-shaped at front of tongue. 6 buds per. Filliform: NO TASTE. Structure. Foliate: TASTE. REAR AND SIDES. Circumvallate: TASTE. LARGE AND CIRCULAR.

How do we perceive proteins and fat? What is the importance of the gut? How do we choose foods?

Glutamate and fat receptors found in the gut because they are too big to be sensed by receptors in the tongue. Gut: Gut signals brain to prefer the foods with fat. Important for survival. Choose: 1) Hard-wired taste preferences based on evolutionary needs. (2) Learned responses to food flavors (signals from gut due to important nutrients)

What are the roles of the insular cortex and the orbitofrontal cortex?

INSULAR: Gustotopic in mammals with "hot spots" for each primary ORBITOFRONTAL: Temperature, touch, smell, taste, etc. (Flavor too)

Anatomically, what is the difference between a taster and a super-taster? What has cross-modality matching told us about taster status? What are some health consequences of taster status?

It's a way to show how different people perceive the intensity of something with the same concentration, by comparing it to a different sensation of equivalent intensity. (Supertasters rate high, like bright light, loud sound)

What aspects of taste are probably coded using labeled-line and which ones are probably coded using cross-fiber patterning?

Labeled-Line: Salty, sweet, and bitter Cross-fiber: More nuanced experience - Milk chocolate vs. Dark Chocolate

Where do fibers of the taste cranial nerves synapse with taste cells?

On axons of cranial nerves. NOT ALL RECEPTOR CELLS SYNAPSE ON NERVE FIBER. Some fibers branch, so >1 cell per fiber, and >1 fiber per cell

What is the taste pore?

Opening of taste bud where chemicals go in and reach microvilli.

What types of somatosensory info do we get from the mouth that is relevant to the entire taste experience? What cranial nerve carries that info?

Pain, Texture, and Temperature. TRIGEMINAL NERVE

Salt: what can affect salt preference and perception?

Preference is affected by early learning. Cl- or Na+ deficiency in infancy = increased preference in adulthood. Infants fed salty foods increased salt preference. Perception: Low Na+ diet = increase in perceived intensity of saltiness

Understand the physiology of the taste receptors: how do salty, sweet, sour and bitter substances each lead to action potentials in the taste nerves?

Salty: Na+ enters through channel on microvilli -> Depolarization allows Na+ and Calcium in through voltage-gated channels -> Neurotransmitter release -> AP in taste nerve Sour: Acids in water have a free hydrogen proton. H+ enters cell through ion channel and blocks K+ channel -> K+ can't leave -> depolarization -> Na+ and Calcium into cell through voltage-gated channels -> Neurotransmitter release -> AP in taste nerve. Bitter, Sweet, and umami: Tastant molecule binds to metabotropic receptor -> G-protein activated -> Calcium let into cell through membrane, Na+ channels opened; potassium channels blocked -> Neurotransmitter release -> AP in taste nerve.

How does the perception of bitter change across the lifespan of women?

Sensitivity to bitter INTENSIFIES with PREGNANCY & DIMINISHES after MENOPAUSE.

Genetically and behaviorally, what is the difference between a non-taster and a taster/supertaster?

Supertasters: Denser populations of fungiform papillae. Can taste prop. Tasters can taste PROP but far less. Non-taster: Cannot taste PROP. Genetically: needs at least one dominant gene. Behaviorally: T & ST taste bitter things as even more bitter. Avoid veggies and alcohol/tobacco. NT more likely to drink/smoke.

For what primary tastes do humans show "specific hungers"? What is some evidence for these? What is necessary for something to be able to cause a specific hunger?

Sweet & Salty. "Body wisdom" The need for a nutrient causes the body to crave it. Insulin injections increase craving for sweets. Nutrient needs to be associated with a sensory cue, it won't work if nutrient doesn't have a taste. (Vitamins)

Sweet: What do you know about the receptors for sweet tastes and their relationship to artificial sweeteners?

Sweet is detected by G Protein-Coupled receptors. In relation to artificial sweeteners: Artificial sweeteners activate the G-Protein-Coupled Receptors. 1 signal from receptor.

What/where are the taste buds, and taste cells?

Taste buds: bud-like clusters of receptor cells (multiple on each papillae) that have an opening (taste pore) that lead to microvilli which contain the receptors. Stimulated by tastants. Taste cells: Located inside taste bud

What cranial nerves innervate the tongue?

Vagus Glossopharyngeal and Chorda Tympani Very Good Cats

Do we differentiate between bitters? Why or why not?

Yes, because the sense of bitter taste is so important for survival, as ingesting a bitter compound may lead to injury or death. We want some, like coffee, or vegetables. t's hard to distinguish between bitters.

Can we differentiate between real sugars and artificial sweeteners, and if so, how?

Yes, we use ADDITIONAL TASTES (like bitter for some artificial sweeteners)

What are the arguments for and against umami being a primary taste?

Yes: Signals protein, therefore plays important role in nutrition. Hot spot for it in insula. (also hot spots for 4 other tastes) No: Imperceptible in many protein-rich foods.

What is the purpose of each of the 4 primary tastes (i.e., what important info do they give us that is necessary for our survival)?

salt: ion/basic element: proper nerve and muscle function, we would die without it sweet: energy, carbohydrates bitter: poisons, toxic chemicals sour: poisons, bacteria/spoiled food umami: building blocks for protein, amino acids

How do bitter and sweet interact with each other?

they INHIBIT each other