10
Taste and Smell
– Chemical Receptors
Taste buds
•
The mouth contains around 10,000 taste buds, most of
which are located on and around the tiny bumps on your
tongue. Every taste bud detects
five primary
tastes
:
o
Sour
o
Sweet
o
Bitter
o
Salty
o
Umami - salts of certain acids (for example
monosodium glutamate or MSG)
•
Each of your taste buds contains 50-100 specialised
receptor cells.
•
Sticking out of every single one of these receptor cells is
a tiny taste hair that checks out the food chemicals in
your saliva.
•
When these taste hairs are stimulated, they send nerve
impulses to your brain.
•
Each taste hair responds best to one of the five basic
tastes.
Smell Receptors or Olfactory receptors
•
Humans able to detect thousands of different smells
•
Olfactory receptors occupy a stamp-sized area in the roof of the nasal cavity, the hollow space inside the
nose
•
Tiny hairs, made of nerve fibers, dangle from all your olfactory receptors. They are covered with a
layer of mucus.
•
If a smell, formed by chemicals in the air, dissolves in this mucus, the hairs absorb it and excite your
olfactory receptors.
•
A few molecules are enough to activate these extremely sensitive receptors.
•
Olfactory Hairs easily fatigued so you do not notice smells
•
Linked to memories - when your olfactory receptors are stimulated, they transmit impulses to your brain
and the pathway is directly connected to the limbic system - the part of your brain that deals with
emotions so you usually either like or dislike a smell
•
Smells leave long-lasting impressions and are strongly linked to your memories
•
Much of what we associate as taste also involves smell – that is why hot foods “taste” different
than “cold” foods