Lecture October 16
Talking about taste, touch, and pain today (ignoring temperature)
When you have a cold and you can't smell well, you also can't taste well - there are
interrelations between smell and taste. The stimulus for taste and the stimulus for
smell are the same - molecules of substances.
Taste buds are the sense organs for taste- they're on all sorts of places in your
mouth. Little bumps on your tongue (capplili, papilli?), taste buds are on these.
Taste buds are leafy, have things that stick out- those things are what grab the
molecules. There are 4 different types of papilli in your mouth, one is to keep food
inside (no taste buds on them, just keep food from falling out), the other 3 do have
taste buds. There could be very few taste buds on a pappili, maybe a lot. You also
have taste buds on other parts of your mouth (like cheeks), over time as you age and
you expose your mouth to things, taste buds die off, in time you taste things
differently than you did when you were younger. Don’t have the same "oomph"
cause you don’t have as many taste buds responding. Part of the reason kids are so
picky, they have a lot of taste buds and are having a different sensation of taste.
If you increase the number of molecules in your mouth, you get an increase in taste.
As you increase the concentration of the substance you're tasting, you're increasing
in a linear fashion. The power law has an exponent (n) of 1, this makes taste a bit
Smell: the issue of adaptation. When you're exposed to a smell you adapt very
quickly, so you cant get the same jolt from the second stimulus. This is more or less
true with taste, you adapt quickly, but you also unadapt very quickly. Within 30
seconds you can get your taste back and be unadapted (pizza and beer example),
alternate what you're eating and you'll get more taste from it.
Can we create a model of taste perception (smell prism, colour wheel, that type
thing.) Yes there is a physical model on taste perception based on the primary taste,
called the taste pyramid. (1)
Your tongue has different responses depending on where the substance lands on
your tongue (tip of your tongue- stronger response) Put something bitter at the tip
of your tongue, tastes more bitter.
Why do we have to taste bitter things? Because anything bitter for you is bad for
you, it’s your body's way of saying "don’t eat that!" Coffee generates a bitter
response because it's bad for you. The front of the tongue is where there's more of a
response because it's your body's way of stopping it early, you taste it early so you
can say "no more".
Skin sense: touch and pain Sense organ is the skin. 3 components to the skin: epidermis, dermis, and sub
cutaneous tissue (I think). Epidermis= top, what you see, can be thinner and thicker
at different places, the cells at the top of the epidermis are dead already. In the
dermis you have all sorts of nerves with interesting names (after people who
discovered them), people have argued that there should be a relationship between
these nerve endings and the touch sense, but it’s hard to make these connections.
Free nerve endings are more in line with pain sense, and corpuscles are more in line
with pressure, but there is no direct relationship, there job