Abstract
Taste and smell are chemical senses, which means that the receptors (chemoreceptors) of these senses respond to chemical stimuli. In order for a substance to produce a taste sensation, it should be ingested in a solution or subsequently dissolved in saliva; a solid substance put in the mouth perfectly dry is tasteless. Therefore, taste receptors or taste buds occur only on wet surfaces, more precisely in the oral cavity in land vertebrates; however, in aquatic animals, these receptors are scattered all over the body. There are functionally different types of receptors for each of the primary tastes and the distribution of each type is not even on the surface of the tongue mucosa. The sweet and sour sensitive buds are located mainly on the tip of the tongue, those sensitive to acids are located on the sides of the tongue and those stimulated by the bitter taste are located towards the back of the tongue and in the epiglottis area. Taste may be generated by substances which touch the taste buds through the blood; thus, histamine injected intravenously causes a metallic taste, glucin a sweet taste, whereas jaundice may trigger a bitter taste due to the big concentration of gallbladder constituents in the blood.
Keywords: taste receptors; taste nerves; taste sensation; chemical compostion; inadequate stimuli