The document provides an overview of the physiology of hearing. It discusses:
1) How sound waves are conducted through the external ear, middle ear bones, and inner ear fluid. The middle ear bones provide impedance matching to transmit sounds to the inner ear.
2) In the inner ear, sound causes the basilar membrane to vibrate, stimulating hair cells. This leads to a change in the hair cell membrane potential and the generation of action potentials in the auditory nerve.
3) Neural signals are transmitted from the cochlear nuclei to the auditory cortex through several structures in the brainstem and thalamus. The auditory pathway shows tonotopic organization and hemispheric specialization for
External ear,tympanic membrane and auditory tube Dr.N.Mugunthan.M.S.,mgmcri1234
External ear,tympanic membrane and auditory tube - Lecture by Dr.N.Mugunthan.M.S.,Associate Professor, Mahatma Gandhi Medical College & Research Institute, Pondicherry,
Sri Balaji Vidyapeeth University.
External ear,tympanic membrane and auditory tube Dr.N.Mugunthan.M.S.,mgmcri1234
External ear,tympanic membrane and auditory tube - Lecture by Dr.N.Mugunthan.M.S.,Associate Professor, Mahatma Gandhi Medical College & Research Institute, Pondicherry,
Sri Balaji Vidyapeeth University.
Physiology of ear.
Basic definition related to sound -hearing,sound,sound wave.
mechanism of hearing
mechanical conduction of sound
transfer action of middle ear
impedence
areal ratio/ hydraulic lever
lever ratio of ossicles
catenary lever
transduction of mechanical energy
travelling wave theory of Bekesy
sound propagation in cochlea
electrical conduction of sound
central auditory pathway
acoustic reflex
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.
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
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.
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
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
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.
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.
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.
Dr. Vidisha Kumari, a leading epidemiologist in Bangalore, emphasizes the importance of getting vaccinated. "The flu vaccine is our best defense against the influenza virus. It not only protects individuals but also helps prevent the spread of the virus in our communities," he says.
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.
Healthcare providers are also stressing the importance of continuing COVID-19 precautions. Wearing masks, practicing good hand hygiene, and maintaining social distancing are still crucial, especially in crowded places.
Protect yourself and your loved ones by getting vaccinated. Together, we can help keep Bangalore healthy and safe this flu season. For more information on vaccination centers and schedules, residents can visit the Karnataka Health Department’s official website or follow their social media pages.
Stay informed, stay safe, and get your flu shot today!
micro teaching on communication m.sc nursing.pdfAnurag Sharma
Microteaching is a unique model of practice teaching. It is a viable instrument for the. desired change in the teaching behavior or the behavior potential which, in specified types of real. classroom situations, tends to facilitate the achievement of specified types of objectives.
Recomendações da OMS sobre cuidados maternos e neonatais para uma experiência pós-natal positiva.
Em consonância com os ODS – Objetivos do Desenvolvimento Sustentável e a Estratégia Global para a Saúde das Mulheres, Crianças e Adolescentes, e aplicando uma abordagem baseada nos direitos humanos, os esforços de cuidados pós-natais devem expandir-se para além da cobertura e da simples sobrevivência, de modo a incluir cuidados de qualidade.
Estas diretrizes visam melhorar a qualidade dos cuidados pós-natais essenciais e de rotina prestados às mulheres e aos recém-nascidos, com o objetivo final de melhorar a saúde e o bem-estar materno e neonatal.
Uma “experiência pós-natal positiva” é um resultado importante para todas as mulheres que dão à luz e para os seus recém-nascidos, estabelecendo as bases para a melhoria da saúde e do bem-estar a curto e longo prazo. Uma experiência pós-natal positiva é definida como aquela em que as mulheres, pessoas que gestam, os recém-nascidos, os casais, os pais, os cuidadores e as famílias recebem informação consistente, garantia e apoio de profissionais de saúde motivados; e onde um sistema de saúde flexível e com recursos reconheça as necessidades das mulheres e dos bebês e respeite o seu contexto cultural.
Estas diretrizes consolidadas apresentam algumas recomendações novas e já bem fundamentadas sobre cuidados pós-natais de rotina para mulheres e neonatos que recebem cuidados no pós-parto em unidades de saúde ou na comunidade, independentemente dos recursos disponíveis.
É fornecido um conjunto abrangente de recomendações para cuidados durante o período puerperal, com ênfase nos cuidados essenciais que todas as mulheres e recém-nascidos devem receber, e com a devida atenção à qualidade dos cuidados; isto é, a entrega e a experiência do cuidado recebido. Estas diretrizes atualizam e ampliam as recomendações da OMS de 2014 sobre cuidados pós-natais da mãe e do recém-nascido e complementam as atuais diretrizes da OMS sobre a gestão de complicações pós-natais.
O estabelecimento da amamentação e o manejo das principais intercorrências é contemplada.
Recomendamos muito.
Vamos discutir essas recomendações no nosso curso de pós-graduação em Aleitamento no Instituto Ciclos.
Esta publicação só está disponível em inglês até o momento.
Prof. Marcus Renato de Carvalho
www.agostodourado.com
2. OBJECTIVES
Stimuli or sound waves.
Conduction of sound
waves.
Transduction of sound
waves.
Neural transmission of
signals.
Encoding of signals.
Applied.
Monday, March 28, 2016
3. AUDITION
For social communication.
Melophobia – fear of music.
The scientific study of sound waves is known
as Acoustics.
Monday, March 28, 2016
5. SOUND WAVES:
Sound travels in
Waves through media
Alternating Compression
(dense molecules) &
Rarefaction (loose
molecules) waves
The simple sound is
the sinusoidal wave or
Pure Tone
6. PROPERTIES OF SOUND THE EAR
DETECTS
1- Pressure level (dB)
2- Frequency (cycle/sec = Hz)
3- Complexity
7. WAVE PATTERNS
A is the record of a pure tone
B has a greater amplitude
and is louder than A.
C has the same
amplitude as A but a greater
frequency, and its pitch is
higher.
D is a complex wave form
that is regularly repeated.
E, which have no regular
pattern, are perceived as
NOISE
8. The Human ear is sensitive to sounds over
a wide range of:
- Frequencies: 20 – 20,000 Hz
- Amplitudes: 0.0002 – 200 dyne/cm2
The human ear can detect the difference
between two sounds occurring 10 μsec
apart in time
HOW SENSITIVE THE EAR TO
SOUNDS?
9. SOUND • Amplitude determines the loudness of sound
• Amplitude is measured in decibels
11. Pitch discrimination is best in the 1000- to
3000-Hz range
Poor at high and low pitches.
Average individuals distinguish 2000 pitchs
Musicians- Cortical Plasticity
The pitch of the average male voice in
conversation is about 120 Hz and
Average female voice about 250 Hz.
PITCH OF SOUND
12. CONDUCTION OF SOUND WAVES.
Role of External Ear
Monday, March 28, 2016
Sound waves are collected by the Pinna and focused into the
External Auditory Canal
The vibration pass down the EAC and strike the TM
13. EXTERNAL EAR FUNCTIONS:
Collecting sound waves
Amplification of frequencies
2000
- 4000 Hz (Resonant
Frequency of EAC)
Providing cues about the
vertical localization of a
sound source (by the Degree of
sound waves reflection over
the Pinna)
14. CONDUCTION OF SOUND
WAVES.
Conduction from
tympanic membrane to
ear ossicles.
Tympanic membrane
Pressure Receiver –
Sensitive to Pressure
Change
Resonator – Vibrate
with Pressure Change.
Critically Dampens as
sound ends.
Monday, March 28, 2016
15. CONDUCTION OF SOUND WAVES
MECHANICALLY FROM MIDDLE EAR
TO INNER EAR
Impedance matching.
Phase differential
between oval and round
window.
Natural resonance of
External Ear and Middle
Ear.
Attenuation Reflex.
Monday, March 28, 2016
16. IMPEDANCE MATCHING.
A person in water can not hear sound
produced out of it.
As 99.9% sound get reflected from surface
of water due to Impedance.
So as Air filled Middle ear conduct sound
to fluid filled Inner ear most of sound get
Reflected – Impedance Mismatching.
Compensated by Inner Ear by
IMPEDANCE MATCHING.
Monday, March 28, 2016
17. IMPEDANCE MATCHING BY EAR
OSSICLES BY 3 MECHANISMS
HYDROLIC ACTION OF
TYMPANIC MEMBRANE –
Effective vibratory area of
tympanic membrane (55mm2)
is more than stapes oval
window surface area(3.2mm2)
So force produced by sound
concentrated over small area
Amplifying Pressure on Oval
Window
Monday, March 28, 2016
18. IMPEDANCE MATCHING BY EAR
OSSICLES BY 3 MECHANISMS
LEVER ACTION OF
VESICLES.
Handle of Malleus 1.3
times longer than Long
process of Incus,
providing Mechanical
Leverage Advantage.
So Ossicles increases
force of movement by
1.3 times.
Monday, March 28, 2016
19. IMPEDANCE MATCHING BY EAR
OSSICLES BY 3 MECHANISMS
CURVED MEMBRANE
EFFECT.
Movement of
Tympanic membrane
more at Periphery
than at Center where
Malleus is attached.
So provide some
leverage.
Monday, March 28, 2016
20. IMPEDANCE MATCHING BY EAR
OSSICLES BY 3 MECHANISMS
So all these together
Increase sound
pressure 22 folds
Impedance
Mismatching is mostly
compensated.
If remove ossicles loud
sound hear as whisper.
Monday, March 28, 2016
21. MINIMUM AUDIBILITY CURVE
Amplification of sound –
greatest between 1000-
3000 Hz.
below 16 & above 20000 Hz
not amplified.
Human ear can perceive
pitch between 16-20000 Hz
Maximum sensitivity 1000-
3000 Hz
Monday, March 28, 2016
22. PHASE DIFFERENTIAL BETWEEN
OVAL AND ROUND WINDOW.
Sound don’t reach both
windows simultaneously.
When oval window receive
compression, round
window receive rarefaction.
If sound reaches
simultaneously no
movement of Perilymph
& no hearing.
Monday, March 28, 2016
23. NATURAL RESONANCE OF
EXTERNAL EAR AND MIDDLE EAR.
Natural Resonance –
allow some frequency to
pass more easily to inner
ear.
External auditory canal –
3000 Hz
Tympanic membrane –
800-1600 Hz.
Middle ear – 800 Hz.
Ossicular chain – 500-2000
Hz.
Monday, March 28, 2016
24. ATTENUATION REFLEX.
Tympanic
reflex/Acoustic reflex
Protective reflex.
Reduces sound pressure
amplitude by Changing
mobility &
Transmission
properties of Ear
ossicles.
Monday, March 28, 2016
26. ATTENUATION REFLEX.
Tensor Tympani – pull
Malleus inwards
Stapedius – pulls
stapes outwards.
Both makes Ossicular
system rigid & no
vibrations.
Sound intensity
Decreased by 30-40 db.
Monday, March 28, 2016
27. ADVANTAGES OF
ATTENUATION REFLEX.
Prevents Damage to cochlea
from loud sound.
Attenuates & Mask all low
frequency environmental
sounds & allow person to
concentrate on sounds above
1000 Hz.
Reduces sound produced
during vocalization &
chewing.
Monday, March 28, 2016
28. TRANSDUCTION OF SOUND
WAVES
Transduction of sound from
Mechanical to Electrical
occur in ORGAN OF CORTI
in inner ear.
Vibration of Basilar
membrane.
Stimulation of hair cells
Membrane potential change in
hair cells
Neural transmission of signals.
Monday, March 28, 2016
29. VIBRATION OF BASILAR
MEMBRANE.
Sound waves from middle
ear pass to inner ear
through Oval window by
in & out movement of
stapes.
Wave spread along Scala
Vestibuli to Scala tympani
as a travelling wave.
As it passes it Vibrate
basilar membrane.
Monday, March 28, 2016
30. STIMULATION OF HAIR CELLS
Movement of basilar
membrane causes organ of
corti to move up & down.
Hair of the outer hair cells are
embedded in Tectorial
Membrane.
As both Tectorial membrane
& basilar membrane moves,
they slide each other with
movement.
Monday, March 28, 2016
31. STIMULATION OF HAIR CELLS
As organ of Corti Moves
up, tectorial membrane
slide foreward moving
stereocilia Away from
limbus.
As organ of Corti Moves
Down, tectorial
membrane slide backward
moving stereocilia
towards limbus.
Monday, March 28, 2016
32. STIMULATION OF
HAIR CELLS
Bending of stereocilia
stimulate hair cells
Depolarization – as
stereocilia bend away
from limbus.
Hyperpolarization –
as stereocilia bends
towards limbus.
Monday, March 28, 2016
33. MEMBRANE POTENTIAL
CHANGE IN HAIR CELLS
Change in membrane
potential is directly
proportional to degree
of displaement.
Describe under 2
conditions
At rest
During stimulation.
Monday, March 28, 2016
34. RESTING MEMBRANE
POTENTIAL FROM HAIR CELLS
At rest 2 potentials are
recorded
Endocochlear potential.
Resting potential of hair
cells.
Monday, March 28, 2016
35. ENDOCOCHLEAR POTENTIAL.
Endolymph in scala media secreted
by stria vascularis has
High conc of Na-K-ATPase & unique
electrogenic K pump
So it has high K conc & electrically
positive to perilymph.
So potential developed between
Endolymph & Perilymph is
Endolymphatic potential or
Endocochlear potential
+ 80 mv.
Monday, March 28, 2016
36. RESTING POTENTIAL OF HAIR
CELLS.
Each hair cell has negative
RMP with -70 mv.
At the upper end of hair cell
potential difference
between ICF & endolymph
is -150 mv
Large negative potential &
lack of K conc difference
make hair cells highly
sensitive.
Monday, March 28, 2016
37. ACTION POTENTIAL IN HAIR
CELLS
Cochlear Microphonic
potential
Gating of K channels is
controlled by movement of
stereocilia.
As stereocilia bend away from
Limbus – K channels open –
Depolarization.
As stereocilia bend towards
Limbus – K channels close–
Hyperpolarization.
Monday, March 28, 2016
38. COCHLEAR MICROPHONIC
POTENTIAL
Similar to generator potential as
No latency or refractory period.
Do not obey all or none law.
Resistance to ischemia & anesthesia.
Base of cochlea respond to all frequency, apex
respond to low frequency of sound.
When organ of corti damaged due to prolonged
exposure to loud sound, potential produced by this
band of sound is abolished.
Monday, March 28, 2016
39. ACTION POTENTIAL IN
AUDITORY NERVE.
As hair cells Depolarize –
Ca channels open – Ca
enters – release synaptic
transmitter – activates
receptor sites on afferent
neurons – Action
Potential.
Loudness of sound
determine Frequency of
Action Potential.
Monday, March 28, 2016
45. SALIENT FEATURES OF
AUDITORY PATHWAY.
Bilateral representation.
Descending pathway.
Role in brain stem & spiral
acoustic reflex.
Role in general arousal.
Spatial organization.
Features of auditory cortex.
Features of other cortical
areas with audition.
Monday, March 28, 2016
46. SALIENT FEATURES OF
AUDITORY PATHWAY.
Bilateral
Representation – form
Medulla onwards ear is
Bilaterally represented
in Auditory pathway.
Descending Pathway –
there is significant
Descending pathway
forming feed-forward &
feedback loop.
Monday, March 28, 2016
47. SALIENT FEATURES OF
AUDITORY PATHWAY.
Role in Brain Stem & Spiral
Acoustic Reflex – Integration
of Visual & Auditory
information occurs due to
interconnection between
Superior & Inferior Colliculi.
Role in General Arousal –
Due to Auditory Pathway
collateral to Reticular
Formation & Cerebellum
Monday, March 28, 2016
48. SALIENT FEATURES OF
AUDITORY PATHWAY.
Spatial Organization – different parts of organ of
corti respond to different frequency.
There is Tonotopic organization in cochlear nuclei
maintained in superior olivary nucleus, inferior colliculus,
MGB & auditory cortex.
Same as Retinotopic organization & Somatotopic
organization.
Monday, March 28, 2016
49. FEATURES OF AUDITORY
CORTEX.
Tonotopic organization.
Column Organization –
Isofrequency Columns – Neurons
have same characteristic frequency.
Summation Columns – Neurons
responsive to binaural than
Monaural inputs.
Suppression Columns – Neurons
less responsive to Binaural than
Monaural stimulation.
Monday, March 28, 2016
50. FEATURES OF OTHER CORTICAL
AREAS WITH AUDITION.
Hemispheric Specialization.
During language learning area
22 concerned with processing
of auditory signals related to
speech is more active on left
than right.
Area 22 on right side is more
concerned with melody, pitch &
sound intensity.
Monday, March 28, 2016
51. FEATURES OF OTHER CORTICAL
AREAS WITH AUDITION.
Plasticity of auditory
pathways.
If person becomes deaf
before language skills
developed, Viewing sign
language activates auditory
association area.
Musicians have larger
auditory area & larger
cerebellum than non-
musicians.
Monday, March 28, 2016
52. NEURAL PROCESSING OF
AUDITORY INFORMATION
Encoding of
Frequency.
Encoding of Intensity
(loudness)
Feature Detection.
Localization of Sound
in space
Monday, March 28, 2016
53. ENCODING OF FREQUENCY.
Human ear can
discriminate sound
between 60-20,000 Hz
range.
Encoding occurs in
cochlear nerve.
Explained by Theories
of Hearing.
Monday, March 28, 2016
55. PLACE THEORY OR BEKESY
TRAVELLING WAVE THEORY
Discriminate sound between 2000-
20000 Hz.
Basilar Membrane is Mechanical
Analyzer of sound frequency.
Pattern of movement of basilar
membrane is that of Travelling Wave.
Basilar membrane Near oval window
vibrate in response to sound of Higher
frequency & Near Apex respond to
Lower Frequency.
Monday, March 28, 2016
56. PLACE THEORY OR BEKESY
TRAVELLING WAVE THEORY
This different response to different frequency is due
to systematic variations in Mechanical Properties
in basilar membrane.
So Higher frequencies are represented in Basal turn
& Lower Near Apex.
So same response by Hair cells & Auditory Nerve
fibres.
Thus there is Spatial Organization of Auditory
pathways from hair cells to Auditory Cortex.
Monday, March 28, 2016
58. FREQUENCY THEORY
Discriminate low frequency
sound below 2000 Hz.
For very low frequency
sound there is
synchronization between
frequency of sound & rate of
discharge through cochlear
nerve.
So Frequency of Action
potential in auditory nerve
determine Loudness than
pitch.
Monday, March 28, 2016
60. PITCH OF SOUND
PITCH – subjective
sensation of frequency
of sound.
Higher frequency
greater is pitch.
Discrimination of pitch
also depend on
Loudness
Duration.
Monday, March 28, 2016
61. ENCODING OF INTENSITY (LOUDNESS)
Occurs at level of cochlear nerve.
Monday, March 28, 2016
62. FEATURE DETECTION.
Higher auditory
centers respond to
particular feature.
CORTICAL Neurons
respond to shift of
Note from high to low
frequency.
Monday, March 28, 2016
63. LOCALIZATION OF SOUND IN
SPACE
Can separate location by 1
degree.
Center – Brain Stem relay
nuclei superior olivary
nucleus.
Clues –
Time lag between entry of
sound in 2 ears
Difference in intensity that
reaches 2 ears.
Monday, March 28, 2016