SHU
TTE
RST
OCKOM
IKR
ONSense of memories
Smells are the sensory impressions that most easily
evoke memories, due to the short distance between the
smell receptors of the nose and the limbic system in which
emotions and memory are processed. The most important
limbic structures are the amygdala and the hippocampus.
Sensory cells
1 In the nasal cavity there is a network of
sensory cells that register
molecules in the air.Olfactory bulb
2A nerve signal is
sent to the
olfactory bulb at the end
of the olfactory nerve.Centre of smell
3 The signals from the nose are registered
and interpreted.THE LIMBIC SYSTEM (PURPLE)The fi fth taste
For decades, schoolchildren had
learned that the tongue has taste
buds for four taste sensations:
sweet, sour, salt, and bitterness.
But in 1908, Japanese chemist
Kikunae Ikeda (1864-1936)
discovered a fifth taste: umami.
Ikeda spotted the umami taste as
he was eating dashi, traditional
Japanese seaweed soup. The soup
had a familiar taste which was
neither sweet nor sour, bitter or
salty. So Ikeda went to his lab to
discover that the secret taste came
from the L-glutamate amino acid.
He named the taste “umami”,
which means “pleasant, savoury
taste” in Japanese.
Fat, carbohydrates and proteins
in food have no taste in themselves,
but they trigger taste sensations
via their break-down products.
The individual sugar molecules
from carbohydrates, mono anddi-saccharides taste sweet,
whereas L-glutamate, which is the
most common building block of
proteins, causes the umami taste.
Umami is rather weak, even
in high concentrations. Since
the 1980s, research in taste has
intensified and, in 2002, scientists
identified the taste receptor
that allows us to taste umami
in high-protein food.PAPILLAESalty: Salty food keeps up
the body’s salt balance. Known
from capers, salty nuts, soy.
Sour: Poisonous or tainted
food often has a sour taste.
Also known from lemons and
other harmless things.
Sweet: Sweet food includes
carbohydrates, which re-
energise you. Known from fruit,
berries, honey, and treacle.
Bitter: Many poisonous
plants have a bitter taste.
Also known from coffee,
green tea, dark chocolate.Umami: Amino acids, which
are the building blocks of enzymes
and proteins in the body, are
responsible for the umami taste,
which is known from bouillon,
Parmesan cheese, fish, shellfish,
mushrooms, and seaweeds.The tongue’s taste areas are located at
the front, the back, and on the sides.On the top side of the
tongue, you will find the
papillae on which the taste
buds are located. They
distinguish between
the different tastes.Tongue taste-testing
The sense of taste is very important for our well-being and survival.
It is the last checkpoint before we eat or drink things that might be
harmful. The sense of taste must both estimate the nutrition value
of the food and protect us against eating something toxic.In the Japanese kitchen, the umami taste
is often marked by the use of seaweeds,
fish, mushrooms, and soy.SHU
TTE
RST
OCKscienceillustrated.com.au | 81