2. Physiology of Smell

3. Structure of the olfactory system

4. Olfactory epithelium

5. Olfactory neurons are short- lived (30-60 days)
Replaced from the basal stem cells
Are bipolar nerve cells
5-20 cilia protrude from dendrite into the layer of mucus
Cilia have specific receptors for odorants (1000 types)
Receptors have:
Low threshold (methylmercaptan)
Rapid adaptation (localized and central), 50% in first second

6. Mucus is secreted by:
Supporting cells
Bowmannś glands
Mucus provide appropriate molecular and ionic
environment for odor detection
Mucus contain odorant- binding proteins (OBP)

11. (Mitral cells)

13. Olfactory signal transmission:
through thalamus to orbitofrontal cortex:
Perception & Discrimination of odors
to amygdala and hypothalamus:
Emotional & Motivational aspects of smell
Bahavioral effects

14. Rapid adaptation, 50% in first second
Localized
Inactivation or desensitization
Central

15. Physiology of Taste

16. Anatomy of a taste bud Adults have 3000 to 10,000 taste buds
Each taste bud contain:
40 Supporting cells
5-18 Taste cells
Basal cells
Life span : ~10 days
Rapid adaptation (1 min)

18. Basic taste sensations
Sweet
Salty
Sour
Bitter
Umami.

20. Sour
Proportional to pH
Lateral surface of tongue (Posterior)
Salty
Cations and anions of ionized salts
Metal ions
Lateral surface of tongue (Anterior)

21. Sweet
Organic compounds, sugars, glycols, amino acids
Inorganic salts of lead
Anterior surface of tongue

22. Long chain organic substances contain nitrogen Alkaloids
Bitter
Long chain organic substances contain nitrogen
Alkaloids
Quinine
Caffeine
Strychnine
Nicotine
Taste threshold lowest for
bitter substances
Caudal surface of tongue

23. Umami
Meaning delicious
Glutamate, monosodium glutamate (MSG)
Is the dominant taste of:
Meat extracts
Aging cheese

24. Abnormality of olfaction & taste
Hyposemia (diminished sense of smell)
Anosemia (complete lack of olfactory sensation)
Causes:
Infections
Head trauma
Particular diseases (Parkinson)
Ageusia (taste blindness)
Hypogeusia (diminished taste sensitivity)
Dysgeusia (disturbed sense of taste)
Captopril and penicillamine, which contain sulfhydryl groups, cause temporary loss of taste sensation

27. The end