OLFACTORY ORGAN OF THE NOSE ::
The receptors for the sensation of smell are found in the roof of nasal cavity The sensation of taste is closely related to that of smell odour often influences the selection of food and our enjoyment of certain dishes For example when one has cold and severe nasal congestion food seems tasteless odour helps to i nitiate the flow of some digestive juices reflexly in much the same way as does the taste
olfactory receptors are specialised bipolar sensory nerve cells These receptors lie in between the supporting cells (substentacular cells) The dendrites of olfactory receptors extend as naked processes which end in cilia The cilia lie in the mucus covering the olfactory mucosa of the nasal chamber The axons unite to form olfactory nerve which goes to the brain
The stimulus for the sensation of smell must be a gaseous substance that becomes dissolved in the fluid of the nasal chamber The fluid stimulates the sensitive olfactory cells in the upper part of the nasal mucosa The amount of stimuli reaching the olfactory area is greatly increased by sniffing The pathway is the olfactory nerve and the cortical interpretation is in the temporal lobe
Some fibres of the trigeminal nerve are also located in the olfactory mucous membrane These fibres respond to irritating substances such as ammonia or pepper and may cause sneezing shortness of breath or some other unpleasant sensation it is because of this response that smelling salts may arouse one who feels fainting
The olfactory receptors are easily fatigued and sensory adoptation for a specific odour can occur rapidly the fatigue causes the loss of ability to recognize a persistent odour but a new odour may be detected at once
Unlike taste with only four stimuli recognised there are number of distinct odours Individual odours in a mixed smell can be distinguished and the memory for odours is very critical people can often recall an odour that has been experienced only once before say a particular scent
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