This document provides an overview of the physiology of olfaction. It discusses:
- The anatomy of olfactory stimulation including the nasal passageways, olfactory mucus, and olfactory epithelium.
- The main cell types in the olfactory epithelium: ciliated olfactory receptors, microvillar cells, supporting cells, and basal cells.
- How odorant molecules stimulate the olfactory receptors and initiate the transduction pathway.
- The pathways that olfactory information takes from the olfactory epithelium to the olfactory bulb and onto various regions in the brain involved in olfaction.
- Theories on olfactory transduction and coding of odorant molecules.
-
olfactory system and functioning, pathway of olfaction, neural tract involved in olfaction , endocrine pathway of olfaction, cells and neurons involved in olfaction
Olfaction is one the major sense. In the following presentation, a brief description of the olfactory system is given. In this following topics are discussed: olfactory membrane, olfactory bulb, odor pathway, anosmia, directional smelling and plasticity. By the end of it, you will be able to describe the olfactory pathway of the nervous system.
olfactory system and functioning, pathway of olfaction, neural tract involved in olfaction , endocrine pathway of olfaction, cells and neurons involved in olfaction
Olfaction is one the major sense. In the following presentation, a brief description of the olfactory system is given. In this following topics are discussed: olfactory membrane, olfactory bulb, odor pathway, anosmia, directional smelling and plasticity. By the end of it, you will be able to describe the olfactory pathway of the nervous system.
Smell & Taste theory updated on 2021 BY PANDIAN M. Pandian M
10.13 & 10.14 Describe and discuss perception of smell and taste sensation
At the end of the session, the first phase MBBS student should be able to
1] Describe the location, structure, and afferent pathways of taste receptors.
2]Describe the location, structure, and afferent pathways of smell receptors.
3]Name the basic taste sensations, identify the five distinct gustatory modalities.
4] describe the cells of a taste bud.
5] explain how taste receptors are activated and explain the mechanism of taste transduction for each taste quality.
6] explain how olfactory receptors are activated and explain the mechanism of olfactory transduction.
7] identify the three cranial nerves that transmit taste information to the cerebral cortex.
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.
- Cranial nerves are nerves that emerge directly from the brain and brain stem.
- There are twelve pairs of cranial nerves
- The olfactory nerve (CN I) is the first and shortest cranial nerve. It is a special visceral afferent nerve, which transmits information relating to smell.
- Embryologically, the olfactory nerve is derived from the olfactory placode (a thickening of the ectoderm layer), which also give rise to the glial cells which support the nerve.
- The olfactory placode eventually invaginates and forms the olfactory pit, which further develops into the nasal cavity and the olfactory epithelium, where olfactory receptor neurons reside.
Flu Vaccine Alert in Bangalore Karnatakaaddon Scans
As flu season approaches, health officials in Bangalore, Karnataka, are urging residents to get their flu vaccinations. The seasonal flu, while common, can lead to severe health complications, particularly for vulnerable populations such as young children, the elderly, and those with underlying health conditions.
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This year, the flu season is expected to coincide with a potential increase in other respiratory illnesses. The Karnataka Health Department has launched an awareness campaign highlighting the significance of flu vaccinations. They have set up multiple vaccination centers across Bangalore, making it convenient for residents to receive their shots.
To encourage widespread vaccination, the government is also collaborating with local schools, workplaces, and community centers to facilitate vaccination drives. Special attention is being given to ensuring that the vaccine is accessible to all, including marginalized communities who may have limited access to healthcare.
Residents are reminded that the flu vaccine is safe and effective. Common side effects are mild and may include soreness at the injection site, mild fever, or muscle aches. These side effects are generally short-lived and far less severe than the flu itself.
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- Video recording of this lecture in English language: https://youtu.be/lK81BzxMqdo
- Video recording of this lecture in Arabic language: https://youtu.be/Ve4P0COk9OI
- Link to download the book free: https://nephrotube.blogspot.com/p/nephrotube-nephrology-books.html
- Link to NephroTube website: www.NephroTube.com
- Link to NephroTube social media accounts: https://nephrotube.blogspot.com/p/join-nephrotube-on-social-media.html
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
Lung Cancer: Artificial Intelligence, Synergetics, Complex System Analysis, S...Oleg Kshivets
RESULTS: Overall life span (LS) was 2252.1±1742.5 days and cumulative 5-year survival (5YS) reached 73.2%, 10 years – 64.8%, 20 years – 42.5%. 513 LCP lived more than 5 years (LS=3124.6±1525.6 days), 148 LCP – more than 10 years (LS=5054.4±1504.1 days).199 LCP died because of LC (LS=562.7±374.5 days). 5YS of LCP after bi/lobectomies was significantly superior in comparison with LCP after pneumonectomies (78.1% vs.63.7%, P=0.00001 by log-rank test). AT significantly improved 5YS (66.3% vs. 34.8%) (P=0.00000 by log-rank test) only for LCP with N1-2. Cox modeling displayed that 5YS of LCP significantly depended on: phase transition (PT) early-invasive LC in terms of synergetics, PT N0—N12, cell ratio factors (ratio between cancer cells- CC and blood cells subpopulations), G1-3, histology, glucose, AT, blood cell circuit, prothrombin index, heparin tolerance, recalcification time (P=0.000-0.038). Neural networks, genetic algorithm selection and bootstrap simulation revealed relationships between 5YS and PT early-invasive LC (rank=1), PT N0—N12 (rank=2), thrombocytes/CC (3), erythrocytes/CC (4), eosinophils/CC (5), healthy cells/CC (6), lymphocytes/CC (7), segmented neutrophils/CC (8), stick neutrophils/CC (9), monocytes/CC (10); leucocytes/CC (11). Correct prediction of 5YS was 100% by neural networks computing (area under ROC curve=1.0; error=0.0).
CONCLUSIONS: 5YS of LCP after radical procedures significantly depended on: 1) PT early-invasive cancer; 2) PT N0--N12; 3) cell ratio factors; 4) blood cell circuit; 5) biochemical factors; 6) hemostasis system; 7) AT; 8) LC characteristics; 9) LC cell dynamics; 10) surgery type: lobectomy/pneumonectomy; 11) anthropometric data. Optimal diagnosis and treatment strategies for LC are: 1) screening and early detection of LC; 2) availability of experienced thoracic surgeons because of complexity of radical procedures; 3) aggressive en block surgery and adequate lymph node dissection for completeness; 4) precise prediction; 5) adjuvant chemoimmunoradiotherapy for LCP with unfavorable prognosis.
New Directions in Targeted Therapeutic Approaches for Older Adults With Mantl...i3 Health
i3 Health is pleased to make the speaker slides from this activity available for use as a non-accredited self-study or teaching resource.
This slide deck presented by Dr. Kami Maddocks, Professor-Clinical in the Division of Hematology and
Associate Division Director for Ambulatory Operations
The Ohio State University Comprehensive Cancer Center, will provide insight into new directions in targeted therapeutic approaches for older adults with mantle cell lymphoma.
STATEMENT OF NEED
Mantle cell lymphoma (MCL) is a rare, aggressive B-cell non-Hodgkin lymphoma (NHL) accounting for 5% to 7% of all lymphomas. Its prognosis ranges from indolent disease that does not require treatment for years to very aggressive disease, which is associated with poor survival (Silkenstedt et al, 2021). Typically, MCL is diagnosed at advanced stage and in older patients who cannot tolerate intensive therapy (NCCN, 2022). Although recent advances have slightly increased remission rates, recurrence and relapse remain very common, leading to a median overall survival between 3 and 6 years (LLS, 2021). Though there are several effective options, progress is still needed towards establishing an accepted frontline approach for MCL (Castellino et al, 2022). Treatment selection and management of MCL are complicated by the heterogeneity of prognosis, advanced age and comorbidities of patients, and lack of an established standard approach for treatment, making it vital that clinicians be familiar with the latest research and advances in this area. In this activity chaired by Michael Wang, MD, Professor in the Department of Lymphoma & Myeloma at MD Anderson Cancer Center, expert faculty will discuss prognostic factors informing treatment, the promising results of recent trials in new therapeutic approaches, and the implications of treatment resistance in therapeutic selection for MCL.
Target Audience
Hematology/oncology fellows, attending faculty, and other health care professionals involved in the treatment of patients with mantle cell lymphoma (MCL).
Learning Objectives
1.) Identify clinical and biological prognostic factors that can guide treatment decision making for older adults with MCL
2.) Evaluate emerging data on targeted therapeutic approaches for treatment-naive and relapsed/refractory MCL and their applicability to older adults
3.) Assess mechanisms of resistance to targeted therapies for MCL and their implications for treatment selection
Prix Galien International 2024 Forum ProgramLevi Shapiro
June 20, 2024, Prix Galien International and Jerusalem Ethics Forum in ROME. Detailed agenda including panels:
- ADVANCES IN CARDIOLOGY: A NEW PARADIGM IS COMING
- WOMEN’S HEALTH: FERTILITY PRESERVATION
- WHAT’S NEW IN THE TREATMENT OF INFECTIOUS,
ONCOLOGICAL AND INFLAMMATORY SKIN DISEASES?
- ARTIFICIAL INTELLIGENCE AND ETHICS
- GENE THERAPY
- BEYOND BORDERS: GLOBAL INITIATIVES FOR DEMOCRATIZING LIFE SCIENCE TECHNOLOGIES AND PROMOTING ACCESS TO HEALTHCARE
- ETHICAL CHALLENGES IN LIFE SCIENCES
- Prix Galien International Awards Ceremony
Pulmonary Thromboembolism - etilogy, types, medical- Surgical and nursing man...VarunMahajani
Disruption of blood supply to lung alveoli due to blockage of one or more pulmonary blood vessels is called as Pulmonary thromboembolism. In this presentation we will discuss its causes, types and its management in depth.
Title: Sense of Smell
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 primary categories of smells and the concept of odor blindness.
Explain the structure and location of the olfactory membrane and mucosa, including the types and roles of cells involved in olfaction.
Describe the pathway and mechanisms of olfactory signal transmission from the olfactory receptors to the brain.
Illustrate the biochemical cascade triggered by odorant binding to olfactory receptors, including the role of G-proteins and second messengers in generating an action potential.
Identify different types of olfactory disorders such as anosmia, hyposmia, hyperosmia, and dysosmia, including their potential causes.
Key Topics:
Olfactory Genes:
3% of the human genome accounts for olfactory genes.
400 genes for odorant receptors.
Olfactory Membrane:
Located in the superior part of the nasal cavity.
Medially: Folds downward along the superior septum.
Laterally: Folds over the superior turbinate and upper surface of the middle turbinate.
Total surface area: 5-10 square centimeters.
Olfactory Mucosa:
Olfactory Cells: Bipolar nerve cells derived from the CNS (100 million), with 4-25 olfactory cilia per cell.
Sustentacular Cells: Produce mucus and maintain ionic and molecular environment.
Basal Cells: Replace worn-out olfactory cells with an average lifespan of 1-2 months.
Bowman’s Gland: Secretes mucus.
Stimulation of Olfactory Cells:
Odorant dissolves in mucus and attaches to receptors on olfactory cilia.
Involves a cascade effect through G-proteins and second messengers, leading to depolarization and action potential generation in the olfactory nerve.
Quality of a Good Odorant:
Small (3-20 Carbon atoms), volatile, water-soluble, and lipid-soluble.
Facilitated by odorant-binding proteins in mucus.
Membrane Potential and Action Potential:
Resting membrane potential: -55mV.
Action potential frequency in the olfactory nerve increases with odorant strength.
Adaptation Towards the Sense of Smell:
Rapid adaptation within the first second, with further slow adaptation.
Psychological adaptation greater than receptor adaptation, involving feedback inhibition from the central nervous system.
Primary Sensations of Smell:
Camphoraceous, Musky, Floral, Pepperminty, Ethereal, Pungent, Putrid.
Odor Detection Threshold:
Examples: Hydrogen sulfide (0.0005 ppm), Methyl-mercaptan (0.002 ppm).
Some toxic substances are odorless at lethal concentrations.
Characteristics of Smell:
Odor blindness for single substances due to lack of appropriate receptor protein.
Behavioral and emotional influences of smell.
Transmission of Olfactory Signals:
From olfactory cells to glomeruli in the olfactory bulb, involving lateral inhibition.
Primitive, less old, and new olfactory systems with different path
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.
Knee anatomy and clinical tests 2024.pdfvimalpl1234
This includes all relevant anatomy and clinical tests compiled from standard textbooks, Campbell,netter etc..It is comprehensive and best suited for orthopaedicians and orthopaedic residents.
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
3. INTRODUCTION
• Senseof smell has been recently heavily
studied because of it’s importance to
human being’s survival.
• It helps to track food , can alert us
todanger like gasleak, fire, rotten
food.
• It is also linked to brain that
process emotion and memory.
4. Olfaction or Olfactory perception
- the sense of smell mediated by a group
of specialised sensory cells in nasal cavity.
Odour
-the property of a substance which gives it
a particular smell.
6. • Olfactory nerve (cranial nerve I) stimulation,
which is necessary for identification of most
odorants, depends on the odorant molecules’
reaching the olfactory mucosa at the top of the
nasal cavity.
7. • Although molecules can reach the olfactory
cleft by diffusion, essentially olfaction requires
some type of nasal airflow.
• During eating, there is a retro nasal flow of
odorant molecules that stimulate the olfactory
receptors at the top of the nose and contribute
greatly to the flavor of the food.
9. • At physiologic
airflow rates,
approximately 50%
of the total airflow
passes through the
middle meatus,
• ~ 35% flowing
through the inferior
meatus
• About 15% flows
through the olfactory
region
10. • Sniffing is an almost universally performed
maneuver when a person is presented with an
olfactory stimulus.
• It increase the number of olfactory molecules
in the olfactory cleft by means of a transient
change in the airflow pattern of the nose.
• A sniff also may allow the trigeminal nerve to
alert the central olfactory neurons that an
odorant is coming.
11.
12. • For molecules to reach the olfactory area, they
must pass through the tall but narrow nasal
passageways.
• The epithelium lining the walls of these
passageways is wet, has variable thickness.
13. 2. Olfactory Mucus
• After the odorant molecules reach the olfactory
region, they must interact with the mucus
overlying the receptor cells.
• The mucus apparently comes from both
Bowman’s glands deep in the lamina propria
(only of serous type in humans) and the
adjacent respiratory mucosa (goblet cells)
14. • To reach the olfactory
receptors, the odorant
molecules must be
soluble in the mucus.
• Changes in the
thickness or
composition of the
mucus can influence
the diffusion time
required for odorant
molecules to reach the
receptor sites
15. • Once in the olfactory mucus-epithelial system,
the rate at which the odorant is cleared also is
important.
• Studies shows that 79% of a radioactively
labeled odorant (butanol) remained trapped in
the mucus 30 minutes after inspiratory
exposure, whereas radioactively labeled octane
cleared rapidly.
16. 3. Olfactory Epithelium
• Located 7 cm inside the nasal cavity, the
olfactory sensory neurons are protected in a 1-
mm-wide crevice of the postero superior nose.
• At the epithelial surface, these bipolar neurons
are exposed to
the outside world
through their
dendrites
and cilia.
17. • A number of research groups have shown that
there is mixing of olfactory and respiratory
epithelial tissues in adult.
• The number of these clumps of respiratory
epithelium, which are found in the olfactory
area, increases with age, suggesting that a loss
of primary olfactory neurons at least partially
explains the decreased olfactory ability
associated with aging.
18. Low magnification of the surface of the nasal cavity taken from a transition
region.
Patches of respiratory (R) epithelium (dark areas) can be seen within the
olfactory (O) region
19. Low-power three-dimensional scanning view of the olfactory epithelium and lamina
propria. The olfactory epithelium (E) overlies a thick connective tissue lamina propria
that contains olfactory axon fascicles (A x) and blood vessels (V) (×248).
• The human
olfactory
epithelium covers
an area of roughly
1 cm2 on each
side.
• The epithelium is
pseudostratified
columnar, and it
rests on a
vascular lamina
propria with no
submucosa
20.
21. • This portion of mucosa can be readily
identified from the rest of the nasal mucosa by
its unique yellowish color.
22. Embryologically
• Olfactory receptors derive from neuroblasts.
These neuroblasts differentiates to form
olfactory placodes.
• The central part of each placode invagiantes
giving rise to olfactory sac.
• Olfactory sac opens anteriorly
23. • Olfactory organ
is the only part of
the body in which
the cell bodies of
neurons lie at the
surface, directly
in contact with
the external
environment.
24. four main cell types
1. ciliated olfactory receptors
2. microvillar cells
3. supporting (sustentacular) cells
4.basal cells
25. The olfactory receptor neuron
• Bipolar
• Club-shaped peripheral “knob” that bears the
cilia.
• Extends odourant receptor-containing cilia
into mucus.
• olfactory nerve 15 to 20 foramina in the
cribriform plate to synapse in the bulb
26. High-power magnification of an olfactory knob with long cilia
gradually tapering as they extend over the epithelial surface. At
the base of individual cilia, a necklace-like structure (arrow) can
be seen on the surface of the olfactory knob
27. • Allison et al estimate the rabbit to have
approximately 50 million olfactory axons,
whereas Jafek estimates humans to have only
6 million bilaterally.
28. • The olfactory ensheathing cells are unique in that
they share characteristics that are common with
Schwann cells and central glial cells.
• Because olfactory neurons - ability to regenerate
and make functional synapses with the olfactory
bulb.
• possible therapeutic potential for repair of
peripheral neuronal injury.
• potential agents for reversing spinal cord injuries
and demyelinating diseases.
29. The microvillar cell
• one tenth as often as the ciliated olfactory
neurons.
• flask-shaped, is located near the epithelial
surface, and has an apical membrane
containing microvilli that project into the
mucus overlying the epithelium
• The deep end of the cell tapers to a thin, axon-
like cytoplasmic projection that proceeds into
the lamina propria.
30. • Low-power
magnification of
fractured olfactory
epithelium
illustrating the axon-
like processes
(arrows) from
microvillar cells (M),
which extend basally
between supporting
cells
31. SUPPORTING CELLS/SUSTENTACULAR
CELLS
• Tall cells have an apical
membrane that joins
tightly with the surface
of the receptor cells and
the microvillar cells.
• Do not generate action
potentials, nor are they
electrically coupled to
each other
32. • Play a role in ion and
water regulation and,
along with
Bowman’s gland
duct cells, contain
xenobiotic enzymes
such as cytochrome
P-450 that likely
contribute to odorant
metabolism.
33. Cross-sectional view
of the olfactory
epithelium showing
the columnar
supporting cells (S)
that extend the full
length of the
epithelium. An
olfactory neuron (O)
with its dendrite and
basal cell (B) can be
seen among
supporting cells
34. BASAL CELLS
• Sit along the basal lamina.
• Two groups of replicating cells
Horizontal basal cells Globose basal cells
are just above positioned between
the basal lamina the horizontal basal
cells & immature
neurons.
35. •The globose basal cells seem to be responsible
for the continuous replacement of olfactory
receptor neurons
36. • During severe insult
→repopulate the
nonneuronal components
of the epithelium .
• The replication cycle is
between 3 and 7 weeks.
• When the new receptor
cell forms, it also projects
its axon to the olfactory
bulb, where it synapses
with second-order
neurons, thereby ensuring
continual olfactory
function and continual
olfactory neuron
replacement.
37. Vomeronasal Organ
• Many mammals have an identifiable pit or groove
in the anteroinferior part of the nasal septum that
contains chemosensitive cells.
• In most of these animals,
a nerve can be identified
connecting these cells to
the central nervous system,
to an accessory olfactory
bulb.
38. • Biopsy studies of the nasal mucosa in the small
pit often seen along the anteroinferior nasal
septum (Jacobson’s organ) show olfactory-like
histology but no central connection.
• Electrical activity
elicited by certain
compounds directly
delivered to the
vomeronasal area has been
shown to cause changes in
blood pressure, heart rate,
and hormonal levels.
39. • It is believed to detect
external chemical
signals called
pheromones.
• These signals, which are
not detected
consciously as odors by
the olfactory system,
mediate human
autonomic,
psychological, and
endocrineresponses.
40. Olfactory Bulb
• Located directly over the cribriform plate.
• first relay station in the olfactory pathway
where the primary olfactory neurons synapse
with secondary neurons.
41. Neural components
are arranged in six concentric layers:
the olfactory nerve
glomerular
External plexiform
mitral cell
internal plexiform
granule cell
42. The receptor cell axons
of the olfactory nerve
layer →the glomeruli
→ synapse with the
dendrites of the
mitral and tufted
cells within the
spherical glomeruli.
43. These second order
cells, in turn, send
collaterals that synapse
within the periglomerular
and external plexiform
layers, resulting in
“reverberating” circuits
in which
negative and positive
feedback occur.
mitral cells modulate their
own output by activating
granule cells (which are
inhibitory to them).
44. • The mitral and
tufted cell axons
project
ipsilaterally to the
primary olfactory
cortex via the
olfactory tract
47. MEDIAL OLFACTORY AREA
• consists of a group of nuclei
• located in the mid basal portions of the brain
immediately
• Contain septal nuclei-
feed into the hypothalamus
and other primitive
portions of the brain’s
limbic system
48. Composed of
prepyriform
pyriform cortex
cortical portion of amygdaloid nuclei.
signal pathways- almost all portions of
limbic system , especially hippocampus-
important for learning like or dislike for
food stuffs.
49. An important feature of the lateral olfactory area is
that many signal pathways from this area also feed
directly into an older part of the cerebral cortex
called the paleocortex in the anteromedial
portion of the temporal lobe.
This is the only area of the entire cerebral
cortex where sensory signals pass directly to the
cortex
without passing first through the thalamus.
50. • The mitral and tufted cell axons project
ipsilaterally to the primary olfactory cortex via
the olfactory tract without an intervening
thalamic synapse
51. Primary olfactory cortex is comprised of the
Anterior Olfactory Nucleus - Pyriform Cortex-
Olfactory tubercle - Entorhinal area - Amygdaloid
Cortex - Corticomedial nuclear group of amygdala.
52. Anterior Olfactory Nucleus
Coordination of inputs from
contalateral olfactory cortex
Transfer of Olfactory memories from one
side to other
Pyriform Cortex
Olfactory discrimination
Amygdala
Emotional response to olfactory stimuli
Entorhinal Cortex
Olfactory Memories
53.
54. Olfactory pathway
• First order neuron :
olfactory Epithelium to glomerulus
• Second order neuron :It is formed of the cells of
the olfactory bulb (mitral cells & Tufted cell)
Passes centrally as the olfactory tract .
• Third order neuron: Pyriform Cortex(Area 28)
contain primary olfactory cortex, which contain
3rd order neuron
55.
56. Very Old Olfactory System
•More primitive responses to olfaction
salivation, primitive emotional drives to
smell
Less Old Olfactory System
• Learned control of food intake
• Aversion to food that have caused nausea &
vomiting
Newer System
• Odour discrimintation & analysis of odour
58. • Soluble binding proteins, like odorant-binding
protein -> enhance the access of odorants to the
olfactory receptors.
• Same odorant-binding protein molecules act to
remove odorant molecules from the region of
the receptor cell after transduction.
59. • The actual transformation of odorant chemical
information into an electrical action potential
occurs as a result of specific interactions
between odorant molecules and receptor
proteins on the surface of olfactory cilia.
• With the binding of the receptor to an odorant,
adenylate cyclase is activated by G protein–
coupled receptors and converts adenosine
triphosphate (ATP) into cyclic adenosine
monophosphate( cAMP).
60. • The cAMP then binds to a Na, Ca ion channel
to allow influx of these ions.
• As more channels open, the cell depolarizes,
and an action potential is produced
61. • Once the peripheral olfactory receptor cells are
depolarized, there begins a convergence of
electrical information toward the olfactory
bulb → glomeruli and mitral / tufted cells of
the olfactory bulb → Olfactory cortex
63. MOLECULAR STRUCTURE
• By Moncrieff 1967
• Suggested that molecular structure is
important.
• No stereospecific olfactory receptors have
been demonstrated.
64. Odour mol + Receptor Photochemical reaction
SIGNALTRANSDUCTION
Receptors containing carotenoids
By Briggs and Duncan,1962
65. By Mozell, 1970
Certain receptors could have a
stereospatial, lock and key form,
and receptor cells fire when the
surface membrane is altered.
67. By Laffort et al,1974
Molecular properties depends on
-molecular volume at boiling point
-proton affinity and donation,
-local polarization within the molecule.
68. Holley and Doving,1977
Nature of smell - Pattern of stimulus within
mucosal configuration of receptor cells
This theory is based on
specific receptor sites &
on their position within olfactory mucosa
69. Vibration Theory
Olfactory Pigment Theory
Enzyme Theory
Penetrating and Puncturing theory
70. Randerbrock 1968
Olfactory perceptors are peptide chains vibrating
in an alpha helix.
Odourant molecules forms a band with peptide
chain modulating the vibration-transmitted to
nerves.
Pigment Theory
Rosenberg 1968
odourant molecule + olfactory pigment- increased
electrical conductivity
71. By Davies
Odourant molecules penetrate membrane
of olfactory receptor cell- diffuse-leaving a
hole.
Leakage of Sodium & pottasium occurs-
nerve impulse
74. TYPESOF OLFACTORY DYSFUNCTION
o Anosmia-absenceof smell
o Hyposmiamicrosmia- diminished olfactorysensitivity
o Dysosmia-distorted senseof smell
o Phantosmia- perception of anodorant when noneis
presentl / Olfactory hallucination.
o Agnosia-inability to classify,contrast, or identify odor
sensationsverbally, eventhough the ability to distinguish
between odorants maybenormal
o Hyperosmia-Abnormally acute smell function (Rare
condition )
75. CLASSIFICATION& ETIOLOGY
• TRANSPORT OLFACTORY LOSS
Olfactory dysfunctions canbe causedby conditions
that interfere with the accessof the odorant to
the olfactory neuro-epithelium due to either
swollen nasalmucous membrane, structural
changesand/or mucussecretion.
Causes-Allergy rhinitis, Bacterial rhinitis and
sinusitis, Congenital abnormality like
encephalocele, Deviated NasalSeptum, Nasal
neoplasms, Nasalpolyps, Nasal surgery,Old age,
Viral infections.
76. • SENSORY OLFACTORY LOSS
Olfactory dysfunctions can be caused by
conditions that damage to the
neuroepithelium.
Causes-Drugs that affect cell turn over and
inhalations of toxic chemicals, viral
infections, neoplasms, radiation therapy.
77. • NEURAL OLFACTORY LOSS
• Olfactory dysfunctions canalso be causedby
conditions that damagethe central olfactory
pathways.
• Causes-AIDS,Alzheimer’s disease,Alcoholism,
Chemical Toxins,Cigarette smoke,Diabetes
Mellitus, Depression, Drugs, Huntington’s chorea,
Hypothyroidism, Kallmann syndrome, Korsakoff
psychosis,Malnutrition, Neoplasm, Neurosurgery,
Parkinson disease,Trauma,Vitamin B12def., Zinc
deficiency
78. APPROACHTO OLFACTORY DYSFUNCTION
A.DETAILEDMEDICALHISTORY
Onset, course, nature of impairment, their previous illness
andthen medications taken.
B. PHYSICALEXAMINATION
Thorough ENT,head and neck examinations including nasal
endoscopy. Aneurological examination emphasizing the
cranial nerves, cerebellar and sensorimotor function is
essential.
Psychological examination like general mood and check
for signsof depression should bedone.
79. C.LABORATORYFINDINGS
• Biopsy of olfactory neuroepithelium can be done
in rarecases
D.IMAGING
• Coronal CTscanand MRI Brain are useful.
80. sudden olfactory loss suggests
the possibility of head trauma, infection,
ischemia, or a psychogenic condition.
Gradual loss
the development of degenerative processes,
progressive obstructive lesions or tumors
within the olfactory receptor region or more
central neural structures.
Intermittent loss can be indicative
of an intranasal inflammatory process.
81. • A family history of smell dysfunction may
suggest
a genetic basis
Kallmann’s syndrome :
Delayed puberty in associationwith anosmia
(with or without midline craniofacial
abnormalities, deafness, and renal anomalies
82. Quantitative Olfactory Testing
(1)verify the validity of the patient’s complaint,
(2)characterize the exact nature and degree of the
problem,
(3) accurately monitor changes in function over
time
(4) detect malingering,
(5)obtain an objective basis for determining
compensation for disability.
83. UNIVERSITYOFPENNSYLVANIA
SMELLIDENTIFICATIONTEST
(UPSIT)
• Most commonly used & most superiorand reliable
test.
• Self-administered in 10-15minutes
• Scoredin <1 minute by non-med person
• Available in variouslanguages
• 40 “scratch & sniff “ patches
• Pt. choosesfrom 4 answers& must choose1
• Candetect malingering
• Dysfunction classified asNormosmia, anosmia, mild,
moderate or severe microsmia, or probable malingering
85. To assess olfaction unilaterally, the naris
contralateral to the tested side should
be occluded without distorting
the nasal valve region. This can be easily
accomplished
by sealing the contralateral naris using a
piece of MicrofoamTM.
The patient is instructed to sniff the
stimulus normally and to exhale through
the mouth.
Such occlusion not only prevents air from
entering the olfactory cleft from the
contralateral naris
86. Olfactory event-related potentials (OERPs)
• synchronized brain electroencephalographic
(EEG) activity induced by repeated pulsatile
presentations of an odorant is isolated from
overall EEG activity
Used as :-
sensitive and useful in detecting malingering
88. DIFFERENTIALDIAGNOSIS
• At present, no psychophysical methods to
differentiate sensory from neural hearingloss.
• History of olfactory lossgivesan important clues
tothe cause.
• Leadingcausesof olfactory dysfunctions are
head trauma and viral infections.
• Headtrauma are more common causeof anosmia
in children and young adults whereas viral
infectionsare more common causein older
adults.
89. • Congenital anosmia occurs in Kallmann syndrome
and also in albinism.
• Meningioma of inferior frontal region is the
most common neoplastic causeof anosmia.
• Dysomiais associatedwith depression.
90. TREATMENT
• Transport olfactory loss
Thefollowing treatments are effective
in restoring senseof smell:
i. Allergy management
ii. Antibiotic therapy
iii. Topicaland systemic glucocorticoid
therapy
iv. Operations for nasalobstruction.
91. • Sensorineural Olfactory loss.
No treatment with demonstrated
efficacyfor Sensorineural Olfactory
loss. Fortunately, spontaneous
recovery occurs.
Someclinicians advocate zinc and
vitamin therapy espVitaminA.