Physiology of Sensory Organ-Nose by Deepansha Singh

1. COLLEGE OF DAIRY AND FOOD TECHNOLOGY
TOPIC:PHYSIOLOGY OF SENSORY ORGAN-NOSE
PRESENTED TO:
Dr. Rashmi Bhinda Maam
PRESENTED BY:
Deepansha Singh
BTECH PART 3 SEM 2

2. Physiological functions of Nose
1. Respiration.
2. Air conditioning.
3. Protection of lower airway.
4. Ventilation and Drainage of PNS.
5. Vocal resonance.
6. Olfaction.

3. INTRODUCTION TO OLFACTION
Olfaction is the chemical sensation of gaseous odorants colloquially referred to as
the ability to smell. The olfactory nerve (cranial nerve one) in coordination with
other neuroanatomical structures in the nasal passages, neurotransmitters, and
the cerebral cortex is responsible for carrying out this intricate chemosensory
process. In humans, olfaction closely couples to other complex functions such as
gustation (taste) and involuntary memory formation. The ability to perceive and
detect orders tends to decline with normal aging.

4. ANATOMY OF OLFACTORY SYSTEM

5. Bone: The hard bridge at the top of your nose is made of bone.
Hair and cilia: Hair and cilia (tiny, hairlike structures) inside your nose trap dirt and particles.
Then they move those particles toward your nostrils, where they can be sneezed out or wiped
away.
Lateral walls (outer walls): The outer walls of your nose are made of cartilage and covered in
skin. The walls form your nasal cavities and your nostrils.
Nasal cavities: Your nose has two nasal cavities, hollow spaces where air flows in and out. They
are lined with mucous membranes.
Nerve cells: These cells communicate with your brain to provide a sense of smell.
Nostrils (nares): These are the openings to the nasal cavities that are on the face.

6. Septum: The septum is made of bone and firm cartilage. It runs down the center of your nose
and separates the two nasal cavities.
Sinuses: You have four pairs of sinuses. These air-filled pockets are connected to your nasal
cavities. They produce the mucus that keeps your nose moist.
Turbinates (conchae): There are three pairs of turbinates located along the sides of both nasal
cavities. These folds inside your nose help warm and moisten air after you breathe it in and help
with nasal drainage

7. IMPORTANT ASPECTS OF ODOR PERCEPTION
1.The prospective odor material must be volatile.
2. The odor-laden air must reach the olfactory receptors.
3. The differences in diffusion rates may be a factor in stimulation.
4. The odor must dissolve in aqueous mucus and then diffuse through it.

8. ODOR DETECTION
The basic requirements are:
1. A substance must be volatile, and the molecules must make contact with
receptors.
2. The volatility of a substance depends on its molecular weight and molecular
bonding properties. The upper limit for "smell ability" is usually a molecular
weight of about 300. Heavy molecular weight substance like proteins starches,
fat and many sugars are too heavy to be odorous.

9. 3. Molecular bonds vary with the chemical compounds and
temperature.
4. Compounds that are more volatile are derived from liquids than
from solids. Increase in temperature increases volatility of both
states.
5. Odoriferous substances, must be adsorbed/adhered to the
chemo-receptors, i.e. it should be soluble to some extent in the
membrane constituents, which consists of lipids, proteins and water.

10. ADAPTATION
Perception of a constant odor diminishes with the elapse of time is
known as adaptation. It results in decline in sensitivity, increase in
threshold. The rate of adaptation is a function of the stimulus
intensity. As the adaptation occurs there may be a progressive change
in the nature of odor. Fatigue for one odor may even raise the
threshold for others.

11. ODOR STIMULI
1. Odor is the property of a substance/s that is perceived in the
human and higher vertebrates, by inhalation in the nasal or oral
cavity, that makes an impression upon the olfactory area of the
body, & that during and as a result of such inhalation , it does not
cause or result in choking, irritation, cooling, warmth, drying,
wetting or other
functions foreign to the olfactory area.
2. Smell is not only a part of the esthetic pleasure in foods but it also
has a protective mechanism. Spoiled foods often have typical and
easily recognizable odors, which cause man to reject them

12. 4. Volatility or vapor pressure is not proportional to its odor.
5. Low carbon alcohol (methyl & ethyl alcohol are particularly insoluble in fats
and have very milk odors while the C4 to C6 alcohol are water and fat soluble and
are having strongly odors.
6. Organic compounds generally elicit odors, but the relation of composition to
odor is extremely variable

13. THEORIES OF OLFACTION
1. AMOORE'S STEREOCHEMICAL TIHEORY
The theory proposes that olfactory receptors are sensitive to the size,
shape and the electronic status of the odorant molecule. Based
somewhat on the lock an essential concept of enzymology, it was
expressed that all odor sensations are based on a combination of
limited number of primary odors and specific nerve receptors site
cavities. This theory is based on nerve impulse electrical conduction.

14. 2. WRIGHT'S VIBRATIONAL THEORY
It has been suggested that the odor stimulus be conveyed at long range from the
source to the nose or antenna by propagated electromagnetic radiation, as by
ultraviolet or more likely infrared lengths. This was further modified by Wright,
suggesting that the odors of the given chemicals are a function of their 'intrinsic
molecular vibration frequencies, within the far infrared region of the
electromagnetic spectrum (100-700 cm-I)

15. 3. BEET'S PROFILE-FUNCTIONAL GROUP THEORY
Beets stated that two molecular attributes were important in determining the characteristic
odor: the form and
bulk of the molecule and the nature and disposition of the functional groups of the molecule.
Theories of olfaction can be listed as follows:
1. VIBRATIONAL THEORY: based on correlation between infrared or raman spectra and odor
quality.
2. MOLECULAR SIZE THEORY: based on the ability of specific odoriferous molecules to fit or fill a
corresponding receptor sites.
3.MOLECULAR SHAPE'THEORY: based on the degree of fit into postulated receptor sites.
4. MOLECULAR INTERACTION THEORIES: dependent upon vapor pressure, solubility and other
bulk characteristics of the volatile compounds.

16. OLFACTORY ABNORMALITIES
1. Cryptosmia : obstruction in nasal passages.
2. Anosmia: temporary / permanent loss of smelling capacity.
3. Hemianosmia or Hyperosmia : excessive response.
4. Merosmia: loss of only certain odors.
5. Heterosmia / Parosmia : false odor perceived
6. Autosmia : odor sensation in absence of odor stimuli
7. Cacosmia : persistent perception of unpleasant odors