SENSATION AND
PERCEPTION
Taste and Smell
Taste and smell are chemical senses. As light
waves stimulate vision and sound waves stimulate sound, chemicals stimulate
taste and smell.
Taste
Taste, or gustation, happens when chemicals
stimulate receptors in the tongue and throat, on the inside of the cheeks, and
on the roof of the mouth. These receptors are inside taste buds, which in turn
are inside little bumps on the skin called papillae. Taste
receptors have a short life span and are replaced about every ten days.
For a long time, researchers believed in the
existence of four tastes: salty, sweet, sour, and bitter. Recently, researchers
have suggested the presence of a fifth taste called umami. The spice monosodium
glutamate (MSG) has an umami taste, as do many protein-rich foods. Taste is
also strongly influenced by smell.
Smell
Smell, or olfaction, happens when chemicals in
the air enter the nose during the breathing process. Smell receptors lie in the
top of the nasal passage. They send impulses along the olfactory nerve to the
olfactory bulb at the base of the brain. Researchers theorize that there are a
great many types of olfactory receptors. People perceive particular smells when
different combinations of receptors are stimulated.
Remembrance of Smells Past
The sense of smell is closely connected with
memory. Most people have had the experience of smelling something, maybe a
certain perfume or spice, and suddenly experiencing a strong emotional memory.
Researchers don’t know exactly why this happens, but they theorize that smell
and memory trigger each other because they are processed in neighboring regions
of the brain.
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