This document summarizes the chemical senses of taste and smell. It discusses the four primary tastes of sour, salty, sweet, and bitter. It describes taste buds, their locations in the tongue, and the mechanisms of taste stimulation and transmission to the brain. For smell, it outlines the olfactory membrane, olfactory cells and cilia, stimulation mechanisms, and transmission of smell signals to the olfactory bulb and brain. It also notes some clinical implications like taste blindness and disorders of smell.
Smell and taste by Pandian M. Dept of Physiology, DYPMCKOP,MHPandian M
Describe the basic features of the neural elements in the olfactory epithelium and olfactory bulb.
Describe signal transduction in odorant receptors.
Outline the pathway by which impulses generated in the olfactory epithelium reach the olfactory cortex.
Describe the location and cellular composition of taste buds.
Name the five major taste receptors and signal transduction mechanisms in these receptors.
Outline the pathways by which impulses generated in taste receptors reach the insular cortex.
Olfaction, or the sense of smell, is an ancient sensory system that together with taste enables an organism to detect chemicals in the external environment. Olfaction is one of the five major human senses (vision, hearing, olfaction, taste, and touch) that occurs when odorants bind to specific sites in olfactory receptors.Olfaction is present in most species such as insects, worms, fish, amphibians, birds, and mammals. It is essential for survival by permitting the location of food, mates, and predators, although in humans, olfaction is often viewed as an esthetic sense capable of triggering emotion and memory.
Smell and taste by Pandian M. Dept of Physiology, DYPMCKOP,MHPandian M
Describe the basic features of the neural elements in the olfactory epithelium and olfactory bulb.
Describe signal transduction in odorant receptors.
Outline the pathway by which impulses generated in the olfactory epithelium reach the olfactory cortex.
Describe the location and cellular composition of taste buds.
Name the five major taste receptors and signal transduction mechanisms in these receptors.
Outline the pathways by which impulses generated in taste receptors reach the insular cortex.
Olfaction, or the sense of smell, is an ancient sensory system that together with taste enables an organism to detect chemicals in the external environment. Olfaction is one of the five major human senses (vision, hearing, olfaction, taste, and touch) that occurs when odorants bind to specific sites in olfactory receptors.Olfaction is present in most species such as insects, worms, fish, amphibians, birds, and mammals. It is essential for survival by permitting the location of food, mates, and predators, although in humans, olfaction is often viewed as an esthetic sense capable of triggering emotion and memory.
Olfaction is very important for us and also for other animals.
Dog’s sense of smell is 1000 times more than humans. People use dog’s keen sense of smell in many ways---
Govt. agencies use specially trained dogs in search and rescue missio
Detection of narcotics.
Detection of forensic cadaver material.
Due to lack of smell the following disorders may be seen---
Anosmia : lack of ability to smell
Hyposmia- decreased ability to smell
Phantosmia- [“hallucinated smell”] often unpleasant in nature
Dysosmia- things smell differently than they should.
Hyperosmia- an abnormally acute sense of smell
Some times olfaction serve as marker for Perkinson’s diseases. Some illness can be diagnosed by their associated smell( e.g. acetone and diabetes). So smell therapy and clinical use of odour is an area for future.
Olfaction is very important for us and also for other animals.
Dog’s sense of smell is 1000 times more than humans. People use dog’s keen sense of smell in many ways---
Govt. agencies use specially trained dogs in search and rescue missio
Detection of narcotics.
Detection of forensic cadaver material.
Due to lack of smell the following disorders may be seen---
Anosmia : lack of ability to smell
Hyposmia- decreased ability to smell
Phantosmia- [“hallucinated smell”] often unpleasant in nature
Dysosmia- things smell differently than they should.
Hyperosmia- an abnormally acute sense of smell
Some times olfaction serve as marker for Perkinson’s diseases. Some illness can be diagnosed by their associated smell( e.g. acetone and diabetes). So smell therapy and clinical use of odour is an area for future.
different type of lower limb amputation with indication, peri-operative care, surgical steps, post op care complication and different type of prosthesis
Other important functions of the kidneys include blood pressure regulation and the production of erythropoietin, which controls red blood cell production in the bone marrow. Kidneys also regulate the acid-base balance and conserve fluids.
Anatomy & Physiology of Renal System.pptxsodha ranbir
This content is helpful for first year students of GNM & B.Sc.(N).
This content provides you easy learning of anatomy & physiology of renal system / excretory system.
Tom Selleck Health: A Comprehensive Look at the Iconic Actor’s Wellness Journeygreendigital
Tom Selleck, an enduring figure in Hollywood. has captivated audiences for decades with his rugged charm, iconic moustache. and memorable roles in television and film. From his breakout role as Thomas Magnum in Magnum P.I. to his current portrayal of Frank Reagan in Blue Bloods. Selleck's career has spanned over 50 years. But beyond his professional achievements. fans have often been curious about Tom Selleck Health. especially as he has aged in the public eye.
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Introduction
Many have been interested in Tom Selleck health. not only because of his enduring presence on screen but also because of the challenges. and lifestyle choices he has faced and made over the years. This article delves into the various aspects of Tom Selleck health. exploring his fitness regimen, diet, mental health. and the challenges he has encountered as he ages. We'll look at how he maintains his well-being. the health issues he has faced, and his approach to ageing .
Early Life and Career
Childhood and Athletic Beginnings
Tom Selleck was born on January 29, 1945, in Detroit, Michigan, and grew up in Sherman Oaks, California. From an early age, he was involved in sports, particularly basketball. which played a significant role in his physical development. His athletic pursuits continued into college. where he attended the University of Southern California (USC) on a basketball scholarship. This early involvement in sports laid a strong foundation for his physical health and disciplined lifestyle.
Transition to Acting
Selleck's transition from an athlete to an actor came with its physical demands. His first significant role in "Magnum P.I." required him to perform various stunts and maintain a fit appearance. This role, which he played from 1980 to 1988. necessitated a rigorous fitness routine to meet the show's demands. setting the stage for his long-term commitment to health and wellness.
Fitness Regimen
Workout Routine
Tom Selleck health and fitness regimen has evolved. adapting to his changing roles and age. During his "Magnum, P.I." days. Selleck's workouts were intense and focused on building and maintaining muscle mass. His routine included weightlifting, cardiovascular exercises. and specific training for the stunts he performed on the show.
Selleck adjusted his fitness routine as he aged to suit his body's needs. Today, his workouts focus on maintaining flexibility, strength, and cardiovascular health. He incorporates low-impact exercises such as swimming, walking, and light weightlifting. This balanced approach helps him stay fit without putting undue strain on his joints and muscles.
Importance of Flexibility and Mobility
In recent years, Selleck has emphasized the importance of flexibility and mobility in his fitness regimen. Understanding the natural decline in muscle mass and joint flexibility with age. he includes stretching and yoga in his routine. These practices help prevent injuries, improve posture, and maintain mobilit
Report Back from SGO 2024: What’s the Latest in Cervical Cancer?bkling
Are you curious about what’s new in cervical cancer research or unsure what the findings mean? Join Dr. Emily Ko, a gynecologic oncologist at Penn Medicine, to learn about the latest updates from the Society of Gynecologic Oncology (SGO) 2024 Annual Meeting on Women’s Cancer. Dr. Ko will discuss what the research presented at the conference means for you and answer your questions about the new developments.
Title: Sense of Taste
Presenter: Dr. Faiza, Assistant Professor of Physiology
Qualifications:
MBBS (Best Graduate, AIMC Lahore)
FCPS Physiology
ICMT, CHPE, DHPE (STMU)
MPH (GC University, Faisalabad)
MBA (Virtual University of Pakistan)
Learning Objectives:
Describe the structure and function of taste buds.
Describe the relationship between the taste threshold and taste index of common substances.
Explain the chemical basis and signal transduction of taste perception for each type of primary taste sensation.
Recognize different abnormalities of taste perception and their causes.
Key Topics:
Significance of Taste Sensation:
Differentiation between pleasant and harmful food
Influence on behavior
Selection of food based on metabolic needs
Receptors of Taste:
Taste buds on the tongue
Influence of sense of smell, texture of food, and pain stimulation (e.g., by pepper)
Primary and Secondary Taste Sensations:
Primary taste sensations: Sweet, Sour, Salty, Bitter, Umami
Chemical basis and signal transduction mechanisms for each taste
Taste Threshold and Index:
Taste threshold values for Sweet (sucrose), Salty (NaCl), Sour (HCl), and Bitter (Quinine)
Taste index relationship: Inversely proportional to taste threshold
Taste Blindness:
Inability to taste certain substances, particularly thiourea compounds
Example: Phenylthiocarbamide
Structure and Function of Taste Buds:
Composition: Epithelial cells, Sustentacular/Supporting cells, Taste cells, Basal cells
Features: Taste pores, Taste hairs/microvilli, and Taste nerve fibers
Location of Taste Buds:
Found in papillae of the tongue (Fungiform, Circumvallate, Foliate)
Also present on the palate, tonsillar pillars, epiglottis, and proximal esophagus
Mechanism of Taste Stimulation:
Interaction of taste substances with receptors on microvilli
Signal transduction pathways for Umami, Sweet, Bitter, Sour, and Salty tastes
Taste Sensitivity and Adaptation:
Decrease in sensitivity with age
Rapid adaptation of taste sensation
Role of Saliva in Taste:
Dissolution of tastants to reach receptors
Washing away the stimulus
Taste Preferences and Aversions:
Mechanisms behind taste preference and aversion
Influence of receptors and neural pathways
Impact of Sensory Nerve Damage:
Degeneration of taste buds if the sensory nerve fiber is cut
Abnormalities of Taste Detection:
Conditions: Ageusia, Hypogeusia, Dysgeusia (parageusia)
Causes: Nerve damage, neurological disorders, infections, poor oral hygiene, adverse drug effects, deficiencies, aging, tobacco use, altered neurotransmitter levels
Neurotransmitters and Taste Threshold:
Effects of serotonin (5-HT) and norepinephrine (NE) on taste sensitivity
Supertasters:
25% of the population with heightened sensitivity to taste, especially bitterness
Increased number of fungiform papillae
The prostate is an exocrine gland of the male mammalian reproductive system
It is a walnut-sized gland that forms part of the male reproductive system and is located in front of the rectum and just below the urinary bladder
Function is to store and secrete a clear, slightly alkaline fluid that constitutes 10-30% of the volume of the seminal fluid that along with the spermatozoa, constitutes semen
A healthy human prostate measures (4cm-vertical, by 3cm-horizontal, 2cm ant-post ).
It surrounds the urethra just below the urinary bladder. It has anterior, median, posterior and two lateral lobes
It’s work is regulated by androgens which are responsible for male sex characteristics
Generalised disease of the prostate due to hormonal derangement which leads to non malignant enlargement of the gland (increase in the number of epithelial cells and stromal tissue)to cause compression of the urethra leading to symptoms (LUTS
Couples presenting to the infertility clinic- Do they really have infertility...Sujoy Dasgupta
Dr Sujoy Dasgupta presented the study on "Couples presenting to the infertility clinic- Do they really have infertility? – The unexplored stories of non-consummation" in the 13th Congress of the Asia Pacific Initiative on Reproduction (ASPIRE 2024) at Manila on 24 May, 2024.
Ethanol (CH3CH2OH), or beverage alcohol, is a two-carbon alcohol
that is rapidly distributed in the body and brain. Ethanol alters many
neurochemical systems and has rewarding and addictive properties. It
is the oldest recreational drug and likely contributes to more morbidity,
mortality, and public health costs than all illicit drugs combined. The
5th edition of the Diagnostic and Statistical Manual of Mental Disorders
(DSM-5) integrates alcohol abuse and alcohol dependence into a single
disorder called alcohol use disorder (AUD), with mild, moderate,
and severe subclassifications (American Psychiatric Association, 2013).
In the DSM-5, all types of substance abuse and dependence have been
combined into a single substance use disorder (SUD) on a continuum
from mild to severe. A diagnosis of AUD requires that at least two of
the 11 DSM-5 behaviors be present within a 12-month period (mild
AUD: 2–3 criteria; moderate AUD: 4–5 criteria; severe AUD: 6–11 criteria).
The four main behavioral effects of AUD are impaired control over
drinking, negative social consequences, risky use, and altered physiological
effects (tolerance, withdrawal). This chapter presents an overview
of the prevalence and harmful consequences of AUD in the U.S.,
the systemic nature of the disease, neurocircuitry and stages of AUD,
comorbidities, fetal alcohol spectrum disorders, genetic risk factors, and
pharmacotherapies for AUD.
These lecture slides, by Dr Sidra Arshad, offer a quick overview of physiological basis of a normal electrocardiogram.
Learning objectives:
1. Define an electrocardiogram (ECG) and electrocardiography
2. Describe how dipoles generated by the heart produce the waveforms of the ECG
3. Describe the components of a normal electrocardiogram of a typical bipolar leads (limb II)
4. Differentiate between intervals and segments
5. Enlist some common indications for obtaining an ECG
Study Resources:
1. Chapter 11, Guyton and Hall Textbook of Medical Physiology, 14th edition
2. Chapter 9, Human Physiology - From Cells to Systems, Lauralee Sherwood, 9th edition
3. Chapter 29, Ganong’s Review of Medical Physiology, 26th edition
4. Electrocardiogram, StatPearls - https://www.ncbi.nlm.nih.gov/books/NBK549803/
5. ECG in Medical Practice by ABM Abdullah, 4th edition
6. ECG Basics, http://www.nataliescasebook.com/tag/e-c-g-basics
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2. SENSE OF TASTE
• 4 PRIMARY SENSATION OF TASTE
• SOUR
• SALTY
• SWEET
• BITTER
3. • SOUR TASTE-
1.IT IS CAUSED BY ACIDS
2.PROPORTIONAL TO THE LOGARITHM OF THE HYDROGEN ION CONCENTRATION
SALTY TASTE-
1.ELICITED BY IONIZED SALTS
2.CATIONS OF SALT ARE MAINLY RESPONSIBLE FOR THE SALTY TASTE.
• SWEET TASTE-LIST OF CHEMICALS CAUSING SWEET TASTE ARE:
1)SUGARS
2)GLYCOLS
3)ALCOHOLS
4)ALDEHYDES
5)KETONES
6)AMIDES
7)ESTERS
4. • BITTER TASTE-SUBSTANCE GIVING BITTER TASTE ARE ALMOST
ENTIRELY ORGANIC SUBSTANCES.
1)LONG CHAIN ORGANIC SUBSTANCES THAT CONTAIN NITROGEN
2)ALKALOIDS. The alkaloids include drugs such as QUININE, CAFFEINE,
STRYCHININE, AND NICOTINE.
5. THRESHOLD FOR TASTE
• SOUR TASTE BY HYDROCHLORIC ACID -0.0009N
• SALTY TASTE BY SODIUM CHLORIDE-0.01M
• SWEET TASTE BY SUCROSE -0.01M
• BITTER TASTE BY QUININE-0.000008M
6. TASTE BLINDNESS
• MANY PEOPLE ARE TASTE BLIND FOR CERTAIN SUBSTANCES
ESPECIALLY FOR DIFFERENT TYPES OF THIOUREA COMPOUNDS.
• SUBSTANCE USED FREQUENTLY FOR DEMONSTRATING TASTE
BLINDNESS IS PHENYLTHIOCARBAMIDE BY PSCYHOLOGISTS.
7. TASTE BUD AND ITS FUNCTION
• COMPOSED OF 50 MODIFIED EPITHELIAL
CELLS.
• SOME SUPPORTING CELLS CALLED
SUSTENTACULAR CELLS.
• OTHER ARE TASTE CELLS.
• TASTE CELLS ARE CONTINUALLY BEING
REPLACED BY MITOTIC DIVISION FROM THE
SURROUNDING EPITHELIAL CELLS.
• OUTER TIP OF TASTE CELLS ARE ARRANGED
AROUND A MINUTE TASTE PORE.
• MICROVILLI OR TASTE HAIR PROTRUDE
OUTWARD INTO THE TASTE PORE TO
APPROACH CAVITY OF MOUTH.
8. • THESE MICROVILLI PRODUCE RECEPTOR SURFACE
FOR TASTE.
• AMONG THE BODIES OF TASTE CELLS IS A
BRANCHING TERMINAL NETWORK OF SEVERAL
TASTE NERVE FIBERS.
• VESICLES FORM BENEATH THE CELL MEMBRANE
NEAR THE FIBERS.
• CONTAINS NEUROTRANSMITTER WHICH IS
RELEASED THROUGH THE CELL MEMBRANE TO
EXCITE THE NERVE FIBER ENDINGS IN RESPONSE
TO TASTE STIMULATION.
9. LOCATION OF TASTE BUDS
• CIRCUMVALLATE PAPILLAE WHICH FORM
A V LINE ON POSTERIOR SURFACE OF THE
TONGUE.
• FUNGIFORM PAPILLAE(moderate
numbers) OVER THE FLAT ANTERIOR
SURFACE OF THE TONGUE.
• FOLIATE PAPILLAE LOCATED IN FOLDS
ALONG THE LATERAL SURFACES OF THE
TONGUE.
• ADULTS HAVE 3000-10,000 TASTE BUDS.
• AT AGE OF 45 YRS MANY TASTE BUDS
DEGENERATE.
10.
11. MECHANISM OF STIMULATION OF
TASTE BUDS
• RECEPTOR POTENTIAL-
MEMBRANE OF TASTE CELL IS NEGATIVELY CHARGED w.r.t OUTSIDE.
TASTE SUBSTANCE ON TASTE HAIRS CAUSES PARTIAL LOSS OF THIS NEGATIVE
POTENTIAL.
TASTE CELL IS DEPOLARIZED.
DECREASE IN POTENTIAL IS APPROXIMATELY PROPORTIONAL TO THE LOGARITHM
OF THE CONCENTRATION OF THE STIMULATING SUBSTANCE.
THIS CHANGE IN POTENTIAL IN TASTE CELL IS THE RECEPTOR POTENTIAL FOR
TASTE.
12. • MECHANISM:
• BINDING OF THE TASTE CHEMICALS TO THE PROTIEN RECEPTOR MOLECULES
THAT PROTRUDE THROUGH THE VILLUS MEMBRANE.
• OPENS ION CHANNELS AND ALLOWS SODIUM IONS TO ENTER AND DEPOLARIZE
THE CELL.
• TASTE CHEMICAL IS GRADUALLY WASHED AWAY FROM THE TASTE VILLUS BY
SALIVA.HENCE REMOVES THE STIMULUS.
• TYPE OF RECEPTOR PROTIEN IN EACH TASTE VILLUS DETERMINES THE TYPE OF
TASTE IT WILL ELICIT.
13. TRANMISSION OF TASTE SIGNALS INTO THE CENTRAL
NERVOUS SYSTEMS
• TASTE IMPULSES FROM ANTERIOR
2/3RD OF TONGUE PASSES FIRST INTO
VTH NERVE.
• THEN THROUGH CHORDA TYMPANI
INTO FACIAL NERVE.
• INTO THE TRACTUS SOLITARIUS IN THE
BRAIN STEM.
• TASTE SENSATION FROM
POSTERIOR1/3RD OF THE TONGUE AND
OTHER POSTERIOR REGION IS
TRANSMITTED BY
GLOSSOPHARYNGEAL NERVE INTO THE
TRACTUS SOLITARIUS BUT AT SLIGHTLY
LOWER LEVEL.
14. • FROM BASE OF THE TONGUE AND
OTHER PARTS OF PHARYNGEAL
REGION TO TRACTUS SOLITARIUS BY
THE VAGUS NERVE.
• ALL TASTE FIBERS SYNAPSE IN THE
NUCLEI OF TRACTUS SOLITARIUS.
• SENDS 2ND ORDER NEURONS TO A
SMALL AREA OF VENTRAL POSTERIOR
MEDIAL NUCLEUS OF THE
THALAMUS.
15. • 3RD ORDER NEURONS FROM
THALAMUS TO THE LOWER TIP OF THE
POSTCENTRAL GYRUS IN THE PARIETAL
CORTEX.
• IT CURLS DEEP INTO SYLVIAN FISSURE
AND INTO ADJACENT
OPERCULARINSULAR AREA.
16. TASTE REFLEXES INTEGRATED IN BRAIN STEM
• FROM TRACTUS SOLITARIUS A LARGE NUMBER OF IMPULSES ARE TRANSMITTED
WITHIN BRAIN STEM DIRECTLY TO INFERIOR AND SUPERIOIR SALIVATORY
NUCLEI.
• THESE INTURN TRANSMIT IMPULSES TO THE SUBMANDIBULAR,
SUBLINGUAL,AND PAROTID GLANDS TO HELP CONTROL THE SECRETION OF
SALIVA DURING THE INGESTION OF THE FOOD.
17. NOTE-
• RECENTLY UMAMI (MEANS DELICIOUS IN JAPANESE) A FIFTH TASTE SENSE HAS
BEEN ADDED TO FOUR CLASSICAL TASTE MODALITIES.
• THE TASTE IS PLEASANT AND SWEET BUT DIFFERS FROM STANDARD SWEET
TASTE.
• MEDIATED BY GLUTAMIC ACID ACTING ON METABOTROPIC GLUTAMATE
RECEPTORS(mGluR4) LOCATED ON TONGUE AND STOMACH.
• GLUTAMIC ACID IS ABUNDANT IN BREAST MILK AND IS PRESENT IN MOST OF THE
NATURAL FOODS eg – CHEESE, MILK, MEAT AND SEAFOOD.
• GLUTAMIC ACID IS CLOSELY INVOLVED IN SMOOTH DIGESTION AND ABSORPTION
OF PROTEINS.
18. APPLIED ASPECTS
1. AGUESIA- IS ABSENCE OF SENSE OF TASTE
SULPHYDRYL GROUP OF DRUGS LIKE CAPTOPRIL AND
PENICILLAMINE OR VITAMIN B12 OR ZINC DEFICIENCIES CAN CAUSE
TEMPORARY LOSS OF TASTE OF SENSATION.
CAN BE DUE TO DAMAGE TO THE LINGUAL OR GLOSSOPHARYNGEAL
NERVE.
2. HYPOGEUSIA- DIMINISHED TASTE SENSITIVITY SEEN WITH AGING
AND TOBACCO USE.
3. DYSGUESIA OR PARAGUESIA- UNPLEASANT DISTURBED
SENSE OF TASTE CAUSE A METTALIC , SALTY, FOUL OR RANACID TASTE.
19. SENSE OF SMELL
• OLFACTORY MEMBRANE-
1. MEDIALLY THE MEMBRANE FOLDS
SLIGHTLY DOWNWARD OVER THE
SURFACE OF THE SUPERIOR
SEPTUM.
2. LATERALLY IT FOLDS OVER THE
SUPERIOR TURBINATE.
3. IN EACH NOSTRIL THE OLFACTORY
MEMBRANE HAS A SURFACE AREA
OF ABOUT 2.4 SQUARE
CENTIMETERS.
20. OLFACTORY CELLS
• RECEPTOR CELLS ARE
OLFACTORY CELLS.
• BIPOLAR CELLS DERIVED
ORIGINALLY FROM CNS.
• 100 MILLION OF THESE CELLS
INTERSPERSED AMONG
SUSTENTACULAR CELLS.
21. • MUCOSAL END OF OLFACTORY
CELLS FORMS KNOB FROM
WHICH 6-12 OLFACTORY HAIRS
OR CILIA PROJECT INTO THE
MUCOUS.
• 0.3 MICROMETER IN DIAMETER
AND 200 MICROMETER IN
LENGTH.
• SPACED AMONG THE
OLFACTORY CELLS ARE MANY
SMALL GLANDS OF BOWMAN
THAT SECRETE MUCOUS ONTO
THE SURFACE OF OLFACTORY
MEMBRANE.
22. STIMULATION OF THE OLFACTORY CELLS
• MECHANISM OF EXCITATION OF
OLFACTORY CELLS
1.THE ODORANT SUBSTANCE
COMING IN CONTACT WITH THE
OLFACTORY SURFACE FIRST
DIFFUSES IN THE MUCOUS THAT
COVERS THE CILIA.
2.IT BINDS WITH THE RECEPTOR
PROTEIN THAT PROTRUDES
THROUGH THE CILIARY
MEMBRANE.
3.THIS RECEPTOR IS A LONG
MOLECULE THAT THREADS ITS WAY
THROUGH THE MEMBRANE SEVEN
TIMES FOLDING INWARD AND
OUTWARDS
23. • THE INSIDE OF FOLDING RECEPTOR IS
COUPLED TO A SO CALLED G-
PROTEIN.CONSIST OF 3 SUBUNITS.
• ON EXCITATION THE ALPHA SUBUNIT
BREAKS FROM G PROTEIN AND
IMMEDIATELY ACTIVATES THE ADENYL
CYCLASE.
• ACTIVATED CYCLASE CONVERTS
INTRACELLULAR ATP TO cAMP.
• cAMP ACTIVATES MEMBRANE
PROTEIN A GATED SODIUM ION
CHANNEL .LARGE NO OF SODIUM ION
POURS INTO THE
CYTOPLASM.INCREASES POSITIVITY
OF THE CELL MEMBRANE AND THUS
EXCITING THE OLFACTORY NEURON
AND TRANSMITTING ACTION
POTENTIAL TO CNS THROUGH
OLFACTORY NERVE.
24. MEMBRANE POTENTIAL AND ACTION POTENTIAL IN OLFACTORY CELLS.
• THE MEMBRANE POTENTIAL OF UNSTIMULATED OLFACTORY CELLS AS
MEASURED BY MICROELECTRODES AVERAGES ABOUT -55 MILLIVOLTS.
• CELLS GENERATE CONTINUOUS ACTION POTENTIAL AT A VERY SLOW RATE
VARYING FROM ONCE EVERY 20 SECS UPTO 2 TO 3 PER SECOND.
• ODORANTS CAUSES DEPOLARIZATION DECREASING THE NEGATIVE POTENTIAL
FROM -55 DOWN TO AS LOW AS -30 MILLIVOLTS OR EVEN LESS.
• NUMBER OF ACTION POTENTIAL INCREASESTO ABOUT 20 PER SECOND WHICH IS
A HIGH RATE FOR THE MINUTE FRACTION OF A MICROMETER OLFACTORY NERVE
FIBERS.
• A FEW ODORANTS HYPERPOLARIZE THE OLFACTORY CELL MEMBRANE WHICH
DECREASES THE NERVE FIRING RATE.
• OLFACTORY RECEPTORS TENDS TO OBEY THE PRINCIPLES OF TRANSDUCTION.
25. TRANSMISSION OF SMELL SIGNALS INTO THE
CENTRAL NERVOUS SYSTEM
• THE OLFACTORY BULB ALSO
KNOWN AS CRANIAL NERVE I IS AN
ANTERIOR OUTGROWTH OF THE
BRAIN TISSUE FROM THE BASE OF
THE BRAIN HAVING BULBOUS
ENLARGEMENT.
• IT LIES ABOVE THE CRIBRIFORM
PLATE SEPERATING THE BRAIN
CAVITY FROM THE UPPER REACHES
OF THE NASAL CAVITY.
• CRIBRIFORM PLATES HAVE
MULTIPLE SMALL PERFORATIONS
THROUGH WHICH AN EQUAL
NUMBER OF SMALL NERVES PASS
UPWARD FROM OLFACTORY
MEMBRANE IN NASAL CAVITY TO
ENTER OLFACTORY BULB IN
CRANIAL CAVITY.
26. • SHORT AXONS TERMINATING IN
MULTIPLE GLOBULAR STRUCTURES
WITHIN THE OLFACTORY BULB CALLED
GLOMERULI .
• EACH OLFACTORY BULB HAS
THOUSANDS OF GLOMERULI AND IT’S
THE TERMINUS FOR ABOUT 25000
AXONS FROM THE OLFACTORY CELLS.
• EACH GLOMERULUS IS THE TERMINUS
FOR DENDRITES FROM 25 LARGE
MITRAL CELLS AND ABOUT 60
SMALLER TUFTED CELLS.
• THESE CELLS IN TURN SENDS AXONS
THROUGH THE OLFACTORY TRACT TO
TRANSMIT OLFACTORY SENSATION TO
THE CNS.
27.
28.
29. APPLED ASPECTS
1. ANOSMIA- COMPLETE ABSENCE OF SENSE OF SMELL.
2. PARAOSMIA- ALTERATION IN CHARACTER OF SMELL.
3. HYPOSMIA- REDUCTION OF THE SENSE OF SMELL.
PATIENTS WITH ADRENAL INSUFFICIENCY HAVE GREATLY INCREASED
SENSITIVITY FOR SMELL.
30. REFERENCES
• GUYTON AND HALL TEXTBOOK OF MEDICAL PHYSIOLOGY 12TH
EDITION.
• A.K JAIN TEXTBOOK OF PHYSIOLOGY VOL II 6TH EDITION.