A Taste of Science

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What do I taste when I taste something?:

What do I taste when I taste something? Our model system: coffee! A Taste of Science

Tasting coffee:

Tasting coffee Hold your nose and taste it Describe the tastes and sensations Use your nose by itself - what do you smell? Do all together! Mmmmmh good!

So how does it work?:

So how does it work?

How taste and smell are wired:

How taste and smell are wired

Where we actually experience the smell or taste:

Where we actually experience the smell or taste

We first encounter a taste here:

We first encounter a taste here We taste salty, sour, bitter, sweet, and perhaps umani (meaty)

One of those little knobby bits:

One of those little knobby bits

PowerPoint Presentation:

Lets look at this

PowerPoint Presentation:

Organized like a bunch of bananas

PowerPoint Presentation:

Taste buds use a bucket brigade of molecules to respond to a taste molecule and send a signal to the brain where we perceive the taste sensation.

Bucket brigade: A talks to B which talks to C:

Bucket brigade: A talks to B which talks to C A B C A taste molecule received by a receptor To a nerve cell Translated into various forms There are two very different bucket brigades in the different taste buds

Deep inside a ‘salty taste’ taste bud:

A bucket brigade transmits the signal through the cell Sour is similar Electrical signal Deep inside a ‘salty taste’ taste bud

The similar thing happens when we taste sweet:

The similar thing happens when we taste sweet What changes are the identity of A, B, and C. Bitter - which is a prominent feature of coffee, is perceived by a similar mechanism

What are A, B and C?:

What are A, B and C? Typically they are proteins or small organic molecules Two basic variations in taste buds Salty/sour Bitter/sweet/umani

Two basic mechanisms:

Two basic mechanisms One uses a receptor that changes the salt concentrations in the cell -> calcium levels One uses a receptor that activates a bucket brigade of proteins that causes calcium to increase One of the most important receptors is that seen in bitter/sweet/umani The receptor is called a G-protein linked receptor

Do taste buds only respond to one taste?:

Do taste buds only respond to one taste? If you looked at the response of one taste bud to a taste molecule What would you predict if the answer was yes? a labeled line code What would you predict if the answer was no? a population code

Each taste bud responds strongly to one type of taste:

Each taste bud responds strongly to one type of taste But they also respond to other tastes as well

Its not this simple:

Its not this simple

What did we learn?:

What did we learn? Taste is not as simple as we once thought Taste buds use two different mechanisms to sense a taste and send a signal to the brain G-protein linked receptors are involved in sensing some tastes Coding is not a simple labeled line code How about smell?

Sniffin’ around the coffee cup:

Sniffin’ around the coffee cup Our sense of smell is key to our enjoyment of the complexities of food and drink

The VNO may also play a role in our behaviors:

The VNO may also play a role in our behaviors In animals this region may govern innate behaviors Sometimes called the ‘sexual nose’ because of its sensitivity to pheromones What does it do in humans?

PowerPoint Presentation:

Wiring is quite Complex Note connection to memory and emotions

What do we smell when we smell?:

What do we smell when we smell? What do we smell in coffee? Malliard reaction A smell experiment using various odors Chemically related compounds and their smells We smell the ‘shape’ of a molecule

Some interesting aspects:

Some interesting aspects We can sense 5-10,000 different odors Small changes can lead to large differences in perception - highly sensitive So how does smelling happen? How is the chemical information encoded and decoded?

Your nasal mucus has these proteins in them:

Your nasal mucus has these proteins in them These bind a wide variety of odor molecules and take them to the receptors

The receptors are located on the sensory cells of the olfactory system:

The receptors are located on the sensory cells of the olfactory system Signal gets processed in these ball-like structures and …. sent to the brain

The receptors:

The receptors Axel and Buck using molecular techniques found that the receptors were G-protein linked receptors We have a lot of these in our genome!

But what’s interesting is how it is wired up:

But what’s interesting is how it is wired up Remember the different colors for the sensory cells? Each sensory cell expresses one receptor type (indicated by color) Each sensory cell type connects to a particular pair of glomeruli Be we only have about 500 or so of the receptor genes!

How the encoding works:

How the encoding works Each sensory cell can bind related molecules with varying affinity Thus multiple glomeruli are activated to varying extents The code is the pattern of glomeruli activation

An experimental example:

An experimental example

Breaking the code:

Breaking the code However, high concentrations of a compound (i. e., indole) may trigger different patterns and result in different perceptions. Why?

Receptors are expressed in sectors in the nasal passage:

Receptors are expressed in sectors in the nasal passage This sectoring is preserved in the olfactory bulb

How it might be decoded:

How it might be decoded Signals from different glomeruli converge and if signals are synchronized, olfactory cortex cells will fire, allowing us to perceive a smell

So what do we know?:

So what do we know? We perceive chemicals through their shape and chemistry We use G-protein linked receptors to recognize and process the chemical signals We have a lot of these genes but less than mice, what might that mean? We perceive smells through a ‘population code’ of activated glomeruli This is different than the ‘labeled line’ code seen in our sense of taste

Hopefully I have given you a sense of how taste and smell work :

Hopefully I have given you a sense of how taste and smell work Enjoy the rest of the day! Source : www.wooster.edu

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