We have been looking at our senses and what parts of the body we use. In particular we have been investigating the tongue. It is a clever little thing it helps us speak, it helps us chew our food by moving it around the mouth and eventually swallow by pushing the food and drink down into our stomach. It is also used for taste.
Mrs Morgan tells us that taste is a very important sense, it guards what goes into our stomach. If we taste something sweet; we know that it probably has sugars that will provide lots of energy for our body. If we taste something bitter it might be poisonous, and we spit it out. If it is sour it might be rotten with lots of dangerous bacteria. In nature salt is often in short supply so like sugar, in order to eat more our brain makes us like the taste.
Mrs Morgan tells us we have about 10,000 taste buds now and these each have about 50-150 receptor cells that are constantly being replaced every 2 weeks or so. As we get older the rate at which new cells are created reduces and 'very old' people in their late 20's may only have 5,000 working taste buds which is why they start like very strong tasting things like hot curries, chili, smelly cheese or beer which tastes very yeuchie to our more sensitive palettes. As we grow older not only will our tastes change but our ability to taste changes too!
When we look at our tongue we can see little lumps that are used to help it grip food and miss tells us that these also contain the very clever little cells that can detect taste. Other taste cells are scattered around the tongue too but where? In order to find out we need to do some thinking.
Mrs Morgan also tells us about the out dated theory of a tongue taste map* Which iss the idea that you can only taste salt or sugar on certain parts of the tongue. Lots of people even doctors and scientists were taught this in the 60's & 70's and did not question it, so even today you can still find books and some websites that still refer to areas of the tongue having these specialised tasting areas.
*The notion of a tongue map can be traced to the German psychologist D.P. Hanig whose thesis was published in 1901. Scientists are a little embarrassed that they just accepted the theory and even expounded it without really testing it for three quarters of a century. It says the tip of your tongue only detects sweet tastes but if you put salt on it you can taste it. The theory was finally debunked in 1974 by scientist Virginia Collings who demonstrated that whilst there were variations in sensitivity to the four basic tastes around the tongue the variations were small and insignificant. She showed that all tastes can be detected anywhere there are taste receptors. As a baby we even had taste buds on the top of our mouths, cheeks and even epiglottis.
We have to think about ways that we can disprove (or agree with) this theory and find out where our taste buds are located on our tongue. Mrs Morgan puts out plates that represent the four main tastes*. Salty Crisps; Bitter Lemon slices; Sour (tartaric acid) sweets, sweet glace cherries. We had to put a piece on different parts of our tongue to see if we could actually taste them then record what we actually found.
We all had a lot of fun doing this experiment, but actually we did a lot of work we all had to think how we could prove or disprove the theory, how we could record our results and compare them with everyone else in the class. Are we recoding that we do not like the taste of fresh lemon or that it is bitter? How should we record it?
As with all experiments we had to think about safety, so before we started Mrs Morgan made sure that we had clean hands and that everything we put in our mouths went in the bin rather than back on the testing plate. When testing the back of the tongue Mrs Morgan warned us about pressing to hard and the gag reflex so we decided the answer was do not press too hard. All this preparation right down to the positioning of the plates in the centre of the table are part of the experiment.
Once we have our results we discuss the individual and the group findings we have and what it means. We found out that the middle part of the tongue near the back did not have many taste buds. Mrs Morgan then makes us think about how we can improve the experiment or additional tests we could do.
Mrs Morgan tells us there are 5 main tastes Sweet, Sour, Bitter, Salty and one called Savoury or "Umami" (pronounced "oo-marmi" Japanese literally meaning "delicious flavour" and identified over 100 years ago by Professor Kikunae Ikeda it is a sort of bacon/MSG taste) and scientists are still debating if there are taste cells that can detect calcium and fats as well as cells that can detect the flow of water.
There is still a huge amount of work to be done to understand the workings of the tongue. Perhaps one day we will be using the skills we learnt to provide experiments that will help us discover and explain the way taste works to the scientific community. It will take a lot of hard work and perseverance but Mrs Morgan has always taught us to 'stick it out!!!!'
Did you know that the tongue is the strongest muscle in the Body? No well your right its just another myth. But again a lot of people were told it was, and it appears in lists and sites like Wiki Answers andYahoo but there is no supporting evidence, it is important that we learn to question such sites. The tongue is in fact made up from sixteen individual muscles! The real answer depends on your definition of strength, it might be Gluteus maximus because of its size. The jaw muscle acts the strongest because of its position on a lever(mechanically speaking i.e. your jaw), other people say its the heart because it obviously keeps beating all our lives. or even the Uterus. Its an important skill not only to sometimes question the answers but even question the question itself, in this case "What do you mean by strength?"
You can see the current year 6 do the experiment this experiment when they were in Year Two in 2004 , and see more photos of previous year two pulling funny faces back in 2003 . have a look at the BBC website here or find out about the worlds longest tongue here on CBBC.