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Sense Organ - Nose & Tongue
2013-02-25, 9:09 PM

Chemoreceptors/Chemical receptors

(Nose & Tongue)

NOSE

                The receptors which are sensitive to smell and taste are called as chemoreceptors.

                Smell and taste are the chemical senses and the other senses like sound and light are the physical senses. The chemical senses always depend on the chemical nature of substance and its solubility in water.

ü  The receptors for sense of smell - Nose

ü  The receptors for sense of taste – Tongue

So, there is a close relationship between these two receptors, hence we are enjoying the smell and taste of the food.

Structure of Nose

·         It is divided into small external and long internal positions.

·         External portion is present on the face and internal portion is separated by a bone or cartilage consisting of two nostrils.

·         Smell is detected by these nostrils i.e... Upper nasal cavity and lower vestibular cavity.

·         Nasal cavity is lined with mucous membrane which secrets mucous to keep the membrane moist and supplied with number of blood vessels containing different types of chemoreceptors cells called as olfactory receptors.

·         These receptors consists cilia which projects into nasal cavity and responsible for sense of smell.

Working process of the nose to the brain by olfactory nerve

·         When air enters the nose the chemicals which are present in the air dissolve in moisture present on mucous membrane. These chemicals are detected by olfactory receptors.

·         From the base of the receptor cell, nerve fibres from different cells pass through the holes present on a plate bony septum which separates the nasal cavity from the rest of the skull.

·         Later these nerve fibres joins to form a large nerve called as olfactory nerve which detects the smell and sends the information to the brain .(analyses the sense of smell).

Relationship between nose and tongue

                There is a close relationship between smell and taste because without smelling we cannot eat. Whenever we smell the food then only we can say the taste of the food. Sometimes we feel the food to be tasteless if we cannot smell it.

ü  Example: Cold, blocked nose. We can also notice that sometimes mere smell of the food tells us the taste of the food and results in mouth watery.



TONGUE

It is the gustatory organ which perceives the taste of the substance and gives the sense of the taste.

In vertebrates except in fishes taste receptors are present on the tongue is absent hence taste receptors present at different locations on the body.

Structure of tongue

The human tongue consist about 10,000 taste buds distributed all over the tongue (dorsal and ventral sides). Each taste bud consist two types of cells as follows

Taste receptors

·         About 5-20 taste receptors are present in the taste bud.

·         Each taste bud contains a small pore like opening on the tongue called as taste pore.

·         Each receptor cell consists free hair like cilium which projects into the cavity, inside this saliva baths the receptor cells

Supporting cells

·         These cells support the taste receptors consisting about 60-20 spindle shaped cells.

·         There are 4 types of taste receptors distributed at different locations as follows

ü  Sour taste receptors: present at along the tongue.

ü  Bitter taste receptors: present at back portion of tongue.

ü  Sweet taste receptors: present at front portion of tongue.

ü  Salt taste receptors: present at front portion of tongue.

o   Hot taste receptors: really it is not a taste just it is a physical sensation which irritates tongue, sour, tongue, can also sense the temperature.

Working process of tongue to the brain by nerve fibres

·         When the food enters the mouth it gives taste to the food and dissolve in saliva.

·         Through the taste pore saliva enters the cavity of taste bud and baths the taste receptors.

·         The receptors come into contact with chemicals and dissolves in the saliva generating small electrical potential.

·         Then the nerve fibre gives off and carries the information to the brain (analysis the sense of taste).



Category: My files | Added by: anve
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