How do We Taste and Smell Things?

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Our nose and mouth have special receptor cells, which when stimulated by chemical molecules, send nerve impulses to the brain. Our tongue is covered with tiny growths or papillae. Some papillae contain small group of cells known as taste buds. Each taste bud contains four to twenty receptor cells with short sensory hair. These hair react to molecules dissolved in the saliva. We can taste four main kinds of tastes. Bitterness is tasted at the back of the tongue, sourness at the sides, sweetness at the front and saltiness can be tasted all over. Our nose has cell receptors at the roof of the nasal cavity. These receptors have sensory hair that branch and project into the mucus that lines the cavity. Molecules in the air dissolve in the mucus and stimulate these hair. There are about 15 kinds of smell receptors which can detect over 10,000 different smells.

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