Question

Describe how the Main Olfactory System works from detection through perception in mammals.

Answer 1

Ans.

• Olfactory system is that part of body which function is to detect smell.
• It consist of nose and nasal cavities supporting olfactory mucous membrane in their upper part to sense smell and form respiratory passages in their lower parts.
• Olfactory signal conduction initiates with the olfactory receptors which are small, slender nerve cells attach in huge quantity to mucous membrane epithelium forming the nasal cavity upper part.
• Cells of every olfactory receptor discharges two processes - a short peripheral dendrite and a long and very thin axon known as olfactory nerve fibre.
• Peripheral dendrites protrudes to the epithelium surface and ends in a ball containing many olfactory hairs.
• Olfactory nerve fibre by passing through one of the bony roof opening of nasal cavity reaches to cranial cavity and enters to olfactory bulb of forebrain.
• Smell is detected upon dissolution of a chemical in thin layer of fluid which covers mucous membrane surface and thus contacts olfactory hairs.
• Receptor cells usually differ within themselves regarding their sensitivities and responsiveness to various odorous sbstances.
• Olfactory nerve fibres reaches to antenna shaped dendrites of large mitral cells in the olfactory bulb and in olfactory signal conduction form second main link.
• Long axons are projected by each mitral cell, some of which move into the olfactory tract formation.
• These are white band of fibre which extend back from the bulb over the forebrain basal surface.
• The cortex of pyriform lobe, which contains olfactory tract fibres, form the final cortical receiving area of the olfactory pathway.
• This region in humans is known as uncus of the hippocampal gyrus.
• Some olfactory tract fibres enters into two further olfactory structures ; the olfactory tubercle and amygdala complex medial part.