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Human Body
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Taste receptors are particularly sensitive to bitter aste. This is an important protective mechanism because nany deadly toxins are bitter and are automatically ejected.
A loss of taste is called hypogeusia; in dysgeusia, things taste wrong or even offensive. Research indicates that trace metal zinc is involved in the proper functioning of the taste buds. Tbe Nose and Olfactory Receptors
The human nose can deteet lower concentration of a volatile substance than are detectable by a gas chromatograph. The sensation of smell requires an actual contact of odour-producing substance with the receptors.
The hair-like dendrites of about 100 million smell receptors occupy an area about the size of a postage stamp in the uppermost portion of the lining of the nasal cavity. The olfactory tract leads into the olfactory area in the cortex of the temporal lobe where the impulses are inter
preted.
Physiology of Smell
In order to stimulate these receptors, a substance must be volatile so that it can be inhaled into the nostril. It must at least be slightly water soluble so that it can dissolve in the mucus coating of the membrane.
The multitude of distinct odours that can be recog. pised, represent various combination of seven primary classes of odour viz. camphoraceous, musky, floral, pepperminty, etherlike, pungent and putrid.
The human sense of smell is almost rudimentary in comparison to that of other animals. Again, it serves more important roles for them than for humans. They secrete odorous pheromones as media of communication, ‘bo tresspassing' sign and sex attractants. However, smell serves a number of functions in human life. The aroma of appetizing food starts a flow of saliva and tones up the digestive organs. It can warn of danger such as toxins lurking in spoiled food. A particular perfume or smell can unlock a whole scene of distant past from the filing cabinet
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