Aim: To demonstrate the function of the olfactory nerve.
Requirements: Clove oil, turpentine oil, alcohol, peppermint oil, eucalyptus oil, etc.
Principle: The olfactory nerve (I) is responsible for perception as well as adaptation of smell. The perception of smell takes place by the pathway summarized below:
- The olfactory receptors lie in the nasal epithelium in the superior portion of the nasal cavity which is activated by odorant stimuli.
- The olfactory impulse is conducted through the olfactory nerve to the olfactory bulb in the frontal cerebral cortex.
- The olfactory bulb neurons carry the impulse through the olfactory tract to the limbic system, thalamus, and primary olfactory area of the temporal cortex which is perceived as smell.
Adaptation to smell is decreasing the sensitivity of the olfactory receptors. In general, a complete insensitivity to certain odors occurs within a minute after exposure to the odorant stimuli. It follows a similar olfactory pathway as described above.
Procedure: Select one healthy subject for the test.
(a) Perception of smell:
- Ask the subject to close the eyes and then occlude one of the nostrils.
- Ask the subject to smell and distinguish the odors of each of the test substances by each nostril separately.
- Record the results as /− for smell perception as per the observation table.
(b) Adaptation to smell:
- Ask the subject to occlude one nostril and to smell the test substance 1 until the smell is no longer detected and the nostril gets adapted.
- Immediately ask the subject to distinguish between the smell of test substances 2 and 3 with the same adapted nostril.
- Record the results as /− for adaptation to smell as per the observation table.
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