TASTE AND SMELL
Dowdey (2007), describes smell as “a chemical sense detected by sensory cells called chemoreceptors” (p. 1). The chemoreceptors are stimulated by odours in the surrounding air and the chemoreceptors send electrical impulses to the brain which are interpreted to provide the sensation of smell.
Before we even perceive smells, the olfactory receptors located high in the nasal cavity must be stimulated by odours (Pfaffmann, 1980). This olfactory receptor is a long thin cell which has several delicate hairs on its end, referred to as cilia. These cilia project through mucus that lines the nasal epithelium. “The end of each receptor narrows to a fine nerve fibre, which … enters the olfactory bulb of the brain through a fine channel in the bony roof of the nasal cavity” (Pfaffmann, 1980, p. 553-554). Pearson Education (2011), illustrates the structure and location of the olfactory receptors in Figure 4 below.
Figure 4. Location and structure of the olfactory receptors in the nasal cavity.
Odours are swept up the nostrils and come in contact with the olfactory epithelium where mucus helps to dissolve these odours. The cilia, olfactory hairs, bind with the odours and when stimulated, the dendrites located under the cilia, send electrical impulses to the olfactory bulb in the brain. In the brain, glomeruli receive the impulses from receptors and pass the information on the other cells in the brain (Dowdey, 2007; Pfaffmann, 1980). The activity of the glomeruli allows the brain to identify smell and distinguish between odours. Figure 5 below, by Pearson Education (2011), illustrates the relationship between the olfactory receptors and the glomeruli in the olfactory bulb.
