This document provides an overview of pain pathways and mechanisms. It defines pain and discusses the different types of pain receptors and fibers that detect and transmit nociceptive signals. It describes the dual pain pathway and outlines the pathways from peripheral receptors to the central nervous system. It also discusses theories of pain and the three systems (sensory-discriminative, motivational-affective, cognitive-evaluative) that interact to produce the pain experience. Finally, it provides details on the nerve supply and innervation of maxillary and mandibular teeth.
Physiology of Pain, Characteristic of pain, Basic consideration of nervous system, Pain receptor, Mechanism of pain causation, Theories of pain, Pathways of pain, Pain Receptors
Pain is defined as an “unpleasant emotional experience usually initiated by a noxious stimulus and transmitted over a specialized neural network to the central nervous system where it is interpreted as such”.
Free nerve endings – responsible for carrying noxious stimulus from both superficial as well as deep somatic and visceral pain sensations therefore reffered as nociceptors
According to type of impulses they carry second order neuron can be classified as –
LOW THRESHOLD MECHANOSENSORY( ligth touch, pressure and Proprioception)
NOCIOCEPTIVE SPECIFIC ( Noxious stimulation)
WIDE DYNAMIC RANGE ( wide range of stimulus intensities from nonnoxious to noxious.
SILENT NOCICEPTORS (It is an afferent neuron that appear to remain or silent to any mechanical stimulation .These neuron become active with tissue injury and add to the nociceptive input entering the CNS.
Pain pathway gate control theory
Pain management
An unpleasant emotional experience usually initiated by noxious stimulus and transmitted over a specialized neural network to CNS where it is interpreted as such.
1. Exteroceptors: arising from receptors from skin & mucosa. sensed at conscious level
E.g. Merkel corpuscles : Tactile receptors.
Free Nerve ending :Perceive superficial pain.
2. Proprioceptors : From musculoskeletal structures.
The presence , positions & movement of body. below conscious levels.
E.g. 1) Muscle spindles : Skeletal muscle fibers. Mechanoreceptors.
2) Free nerve ending : Perceive deep somatic pain & other sensations.
3. Interoceptors : From viscera of body below conscious level.
E.g. Pacinian corpuscles : perception of touch-pressure.
Free nerve ending : Perceive visceral pain & other sensations.
Physiology of Pain, Characteristic of pain, Basic consideration of nervous system, Pain receptor, Mechanism of pain causation, Theories of pain, Pathways of pain, Pain Receptors
Pain is defined as an “unpleasant emotional experience usually initiated by a noxious stimulus and transmitted over a specialized neural network to the central nervous system where it is interpreted as such”.
Free nerve endings – responsible for carrying noxious stimulus from both superficial as well as deep somatic and visceral pain sensations therefore reffered as nociceptors
According to type of impulses they carry second order neuron can be classified as –
LOW THRESHOLD MECHANOSENSORY( ligth touch, pressure and Proprioception)
NOCIOCEPTIVE SPECIFIC ( Noxious stimulation)
WIDE DYNAMIC RANGE ( wide range of stimulus intensities from nonnoxious to noxious.
SILENT NOCICEPTORS (It is an afferent neuron that appear to remain or silent to any mechanical stimulation .These neuron become active with tissue injury and add to the nociceptive input entering the CNS.
Pain pathway gate control theory
Pain management
An unpleasant emotional experience usually initiated by noxious stimulus and transmitted over a specialized neural network to CNS where it is interpreted as such.
1. Exteroceptors: arising from receptors from skin & mucosa. sensed at conscious level
E.g. Merkel corpuscles : Tactile receptors.
Free Nerve ending :Perceive superficial pain.
2. Proprioceptors : From musculoskeletal structures.
The presence , positions & movement of body. below conscious levels.
E.g. 1) Muscle spindles : Skeletal muscle fibers. Mechanoreceptors.
2) Free nerve ending : Perceive deep somatic pain & other sensations.
3. Interoceptors : From viscera of body below conscious level.
E.g. Pacinian corpuscles : perception of touch-pressure.
Free nerve ending : Perceive visceral pain & other sensations.
Muscles of mastication are the group of muscles that help in movement of the mandible as during chewing and speech. We need to study these muscles as they control the opening & closing the mouth & their role in the equilibrium created within the mouth. They also play a role in the configuration of face.
Pain is one of the most commonly experienced symptom . It is often spoken of as a protective mechanism since it is usually manifested when an environmental change occurs that causes injury to responsive tissue
Pain is one of the most commonly experienced symptom . It is often spoken of as a protective mechanism since it is usually manifested when an environmental change occurs that causes injury to responsive tissue
Pain is the common symptom in many chronic conditions such as cancers, neuropathies, and chronic disease. It is also experienced in trauma varying from mild to severe based on the location and degree of trauma. This presentation is a brief outline on types of pain, classification of pain, pain pathways and management of pain
https://userupload.net/s5uyonki1n7m
Pain is a somatic and emotional sensation which is unpleasant in nature and associated with actual or potential tissue damage. Physiologically, the function of pain is critical for survival and has a major evolutionary advantage. This is because behaviours which cause pain are often dangerous and harmful, therefore they are generally not reinforced and are unlikely to be repeated.
Muscles of mastication are the group of muscles that help in movement of the mandible as during chewing and speech. We need to study these muscles as they control the opening & closing the mouth & their role in the equilibrium created within the mouth. They also play a role in the configuration of face.
Pain is one of the most commonly experienced symptom . It is often spoken of as a protective mechanism since it is usually manifested when an environmental change occurs that causes injury to responsive tissue
Pain is one of the most commonly experienced symptom . It is often spoken of as a protective mechanism since it is usually manifested when an environmental change occurs that causes injury to responsive tissue
Pain is the common symptom in many chronic conditions such as cancers, neuropathies, and chronic disease. It is also experienced in trauma varying from mild to severe based on the location and degree of trauma. This presentation is a brief outline on types of pain, classification of pain, pain pathways and management of pain
https://userupload.net/s5uyonki1n7m
Pain is a somatic and emotional sensation which is unpleasant in nature and associated with actual or potential tissue damage. Physiologically, the function of pain is critical for survival and has a major evolutionary advantage. This is because behaviours which cause pain are often dangerous and harmful, therefore they are generally not reinforced and are unlikely to be repeated.
Pain as an unpleasant emotional experience usually initiated by a noxious stimulus and transmitted over a specialized neural network to the central nervous system where it is interpreted as such
These simplified slides by Dr. Sidra Arshad present an overview of the non-respiratory functions of the respiratory tract.
Learning objectives:
1. Enlist the non-respiratory functions of the respiratory tract
2. Briefly explain how these functions are carried out
3. Discuss the significance of dead space
4. Differentiate between minute ventilation and alveolar ventilation
5. Describe the cough and sneeze reflexes
Study Resources:
1. Chapter 39, Guyton and Hall Textbook of Medical Physiology, 14th edition
2. Chapter 34, Ganong’s Review of Medical Physiology, 26th edition
3. Chapter 17, Human Physiology by Lauralee Sherwood, 9th edition
4. Non-respiratory functions of the lungs https://academic.oup.com/bjaed/article/13/3/98/278874
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
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
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
Acute scrotum is a general term referring to an emergency condition affecting the contents or the wall of the scrotum.
There are a number of conditions that present acutely, predominantly with pain and/or swelling
A careful and detailed history and examination, and in some cases, investigations allow differentiation between these diagnoses. A prompt diagnosis is essential as the patient may require urgent surgical intervention
Testicular torsion refers to twisting of the spermatic cord, causing ischaemia of the testicle.
Testicular torsion results from inadequate fixation of the testis to the tunica vaginalis producing ischemia from reduced arterial inflow and venous outflow obstruction.
The prevalence of testicular torsion in adult patients hospitalized with acute scrotal pain is approximately 25 to 50 percent
ARTIFICIAL INTELLIGENCE IN HEALTHCARE.pdfAnujkumaranit
Artificial intelligence (AI) refers to the simulation of human intelligence processes by machines, especially computer systems. It encompasses tasks such as learning, reasoning, problem-solving, perception, and language understanding. AI technologies are revolutionizing various fields, from healthcare to finance, by enabling machines to perform tasks that typically require human intelligence.
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
- 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
3. • Pain is a sensory experience of
special significance to physicians
and basic scientists.
• Pain is the commonest symptom
which physicians are called upon
to treat.
• Apart from its obvious applied
value, study of physiology of pain
has taught us a lot about neural
function in general.
• Pain is an intensely subjective
experience, and is therefore
difficult to describe.
4. The International Association for the Study
of Pain
Pain is "an unpleasant sensory and
emotional experience associated with
actual or potential tissue damage, or
described in terms of such damage"
• Monheim : “An unpleasant emotional
experience usually initiated by noxious
stimulus and transmitted over a specialized
neural network to the CNS where it is
interpreted as such.”
5. PAIN
Somatic
(somasthetic)
Visceral (from viscera)
e.g. angina pectoris,
peptic ulcer, intestinal
colic, renal colic, etc.
Superficial (from skin &
subcutaneous tissue) e.g.
superficial cuts/burns, etc.
Deep (from
muscles/bones/fascia/periosteum)
e.g. fractures/arthritis/fibrositis,
rupture of muscle belly
6. The experience of painThe experience of pain
Three systems interact usually to produce pain:Three systems interact usually to produce pain:
1.1. sensory - discriminativesensory - discriminative
2. motivational - affective2. motivational - affective
3. cognitive - evaluative3. cognitive - evaluative
1. Sensory - discriminative system1. Sensory - discriminative system processes informationprocesses information
aboutabout
the strength, intensity, quality and temporal and spatialthe strength, intensity, quality and temporal and spatial
aspects of painaspects of pain
2. Motivational - affective system2. Motivational - affective system determines the individual´sdetermines the individual´s
approach-avoidance behavioursapproach-avoidance behaviours
3. Cognitive - evaluative system3. Cognitive - evaluative system overlies the individualsoverlies the individuals
learnedlearned
behaviour concerning the experience of pain. It maybehaviour concerning the experience of pain. It may
7.
8. • Sensory input from various external stimuli is thought
to be received by specific peripheral receptors that act
as transducers and transmit by nerve action potentials
along specific nerve pathways toward the central
nervous system.
• Termed first–order afferents, these peripheral terminals
of afferent nerve fibers differ in the form of energy to
which they respond at their respective lowest stimulus
intensity, that is, are differentially sensitive.
• The impulse interpreted is nociceptive (causing pain)
if it exceeds the pain threshold, that is, the intensity of
the stimulus is so great that the receptor is no longer
differentially sensitive.
10. • A nerve ending that responds to noxious stimuli that
can actually or potentially produce tissue damage.
• Free nerve endings i.e., they are not enclosed in a
capsule. The receptors for fast pain are sensitive to
mechanical or thermal stimuli of noxious strength. The
receptors for slow pain are sensitive not only to
noxious mechanical and thermal stimuli but also to a
wide variety of chemicals associated with
inflammation.
• These substances include histamine, serotonin,
bradykinin, acetylcholine, potassium ions and
hydrogen ions. It is possible that noxious
mechanical and thermal stimuli also act through the
release of some of these chemicals.
11. • Since pain receptors respond to a wide
variety of stimuli, they are called
polymodal.
• Types of nociceptors :
Aδ Mechanical Nociceptors
C Polymodal Nociceptors
C fibre mechanical nociceptors
High threshold cold nociceptors
12. • Mechanoreceptors, which respond to tactile non
painful stimuli, can be assessed psychophysically
by the ability of a human subject to discriminate
whether application of a two blunt-point stimuli is
perceived as one or two points.
• These receptors are divided into two functional
groups (rapidly or slowly adapting) depending on
their response during stimuli.
• Rapidly adapting mechanoreceptors respond at the
onset and offset of the stimuli, while slowly
adapting mechanoreceptors respond throughout
the stimuli duration.
13. • Mechanoreceptors can be divided into those
expressed in:
Hairy skin (hair follicle receptors):
• Low threshold, rapidly adapting.
• Three major subtypes: ‘down’, ‘guard’,
tylotrich’.
Glabrous (hairless) skin:
• Small receptive fields.
• Two major subtypes: ‘Meissener’s capsule’
(rapidly adapting) and ‘Merkel’s disc’
(slowly adapting).
14. • Proprioception (limb position sense), which
refers tooth position and movement of the
limbs (kinaesthesia), is determined by
mechanoreceptors located in skin, joint
capsules and muscle spindles.
• The CNS integrates information received
from these receptors, while keeping track of
previous motor responses that initiated limb
movement – a process known as efferent copy
or corollary discharge (reviewed by
Matthews, 1982).
15.
16. • Nociception is the neural mechanism by which an individual
detects the presence of a potentially tissue harming stimulus.
There is no implication of (or requirement for) awareness of this
stimulus.
• The nociceptive mechanism (prior to the perceptive event)
consists of a multitude of events as follows:
• Transduction:
• This is the conversion of one form of energy to another. It occurs
at a variety of stages along the nociceptive pathway from:
– Stimulus events to chemical tissue events.
– Chemical tissue and synaptic cleft events to
- Electrical events in neurones.
– Electrical events in neurones to chemical events at synapses.
17. • Transmission:
• Electrical events are transmitted along
neuronal pathways, while molecules in the
synaptic cleft transmit information from
one cell surface to another.
• Modulation:
• The adjustment of events, by up- or down
regulation. This can occur at all levels of
the nociceptive pathway, from tissue,
through primary (1°) afferent neurone and
dorsal horn, to higher brain centres.
• Thus, the pain pathway as described
by Descartes has had to be adapted
with time.
20. • According to this view, pain is produced when any
sensory nerve is stimulated beyond a certain level.
• In other words pain is supposed to be a non-specific
sensation and depends only on high intensity
stimulation.
• But the trigeminal system provides an example
against this theory. In case of trigeminal neuralgia
the patient can suffer excruciating pain from a
stimulus no greater than a gentle touch provided it is
applied to a trigger zone.
• Although, the intensity theory is not accepted, it
remains true to say that intensity of stimulation is a
factor in causing pain.
21. (Johannes Muller, 1842):
• According to this view, pain is a specific modality
equivalent to vision and hearing etc.
• Just as there are Meissner corpuscles for the sensation of
touch, Ruffini end organs supposedly for warmth and
Krause end organs supposedly for cold, so also pain is
mediated by free nerve endings.
• Certain psychophysical studies have been regarded as
supporting specificity theory. Specialization is known to
exist in nervous system and there are well known tracts.
• But concept of specific nerve ending is no long tenable.
The Krause and Ruffini endings are absent from the dermis
of about all hairy skin, so it is certain that these structures
cannot be receptors for cold and warmth.
22. • Head and Rivers (1908) postulated the existence of
two cutaneous sensory nerves extending from the
periphery to the CNS.
• The protopathic system is primitive, yielding diffuse
impression of pain, including extremes of
temperature and is upgraded.
• The epicritic system is concerned with tough
discrimination and small changes in temperature and
is phylogenetically a more recent acquisition.
23.
24. • This theory proposed by Melzack and Wall in
1965 and recently re-evaluated is receiving
considerable attention.
• This theory of pain takes into account the
relative in put of neural impulses along large and
small fibers, the small nerve fibers reach the
dorsal horn of spinal cord and relay impulses to
further cells which transmit them to higher
levels.
• The large nerve fibers have collateral branches,
which carry impulses to substantia gelatinosa
where they stimulate secondary neurons.
25.
26.
27. The role of the afferent and efferent pathwaysThe role of the afferent and efferent pathways
inin
processing of pain informationprocessing of pain information
Nociceptive painNociceptive pain
Nociceptors:Nociceptors: Endings of small unmyelinated and lightlyEndings of small unmyelinated and lightly
myelinated afferent neuronsmyelinated afferent neurons
Stimulators:Stimulators: Chemical, mechanical and thermal noxaeChemical, mechanical and thermal noxae
Mild stimulationMild stimulation →→ positive, pleasurable sensationpositive, pleasurable sensation
(e.g. tickling)(e.g. tickling)
Strong stimulationStrong stimulation →→ painpain
These differences are a result of the frequencyThese differences are a result of the frequency
and amplitude of the afferent signal transmittedand amplitude of the afferent signal transmitted
from the nerve endings to the CNSfrom the nerve endings to the CNS
Location:Location: In muscles, tendons, epidermis, subcutanous tissue,In muscles, tendons, epidermis, subcutanous tissue,
visceral organsvisceral organs
-- they are not evenly distributed in the bodythey are not evenly distributed in the body
(in skin more then in internal structures(in skin more then in internal structures ))
28. Afferent pathways:Afferent pathways:
•• From nociceptorsFrom nociceptors →→ transmittedtransmitted by small A-delta fibers andby small A-delta fibers and
C- fibersC- fibers to the spinal cordto the spinal cord →→ form synapses with neuronsform synapses with neurons
in the dorsal horn(DH)in the dorsal horn(DH)
•• From DHFrom DH →→ transmitted to higher parts of the spinal cordtransmitted to higher parts of the spinal cord
and to the rest of the CNS by spinothalamic tractsand to the rest of the CNS by spinothalamic tracts
**TheThe small unmyelinated C- neuronssmall unmyelinated C- neurons are responsible for theare responsible for the
transmission oftransmission of diffuse burning or aching sensationsdiffuse burning or aching sensations
**Transmission through the larger, myelinated A- delta fibersTransmission through the larger, myelinated A- delta fibers
occurs much more quickly. A - fibers carryoccurs much more quickly. A - fibers carry well-localized,well-localized,
sharp pain sensationssharp pain sensations
29. Efferent analgesic systemEfferent analgesic system
Its role: - inhibition of afferent pain signalsIts role: - inhibition of afferent pain signals
Mechanisms:Mechanisms:
- pain afferents stimulates the neurons- pain afferents stimulates the neurons in periaqueductalin periaqueductal
graygray ((PAG) -PAG) - gray matter surrounding the cerebralgray matter surrounding the cerebral
aqueductaqueduct in the midbrain results inin the midbrain results in activation of efferentactivation of efferent
(descendent) anti-nociceptive pathways(descendent) anti-nociceptive pathways
-- from there the impulses are transmitted throughfrom there the impulses are transmitted through
the spinalthe spinal cord tocord to the dorsal hornthe dorsal horn
-- there thaythere thay inhibit or block transmission of nociceptiveinhibit or block transmission of nociceptive
signals at the level of dorsal hornsignals at the level of dorsal horn
30. The role of the spinal cord in pain processingThe role of the spinal cord in pain processing
•• MostMost afferent pain fibersafferent pain fibers terminate in the dorsal hornterminate in the dorsal horn of theof the
spinal segment that they enter. Some, howeverspinal segment that they enter. Some, however ,, extendextend
toward the head or the foot for several segments beforetoward the head or the foot for several segments before
terminatingterminating
•• The A-The A- ββ fibers, some large A-delta fibers and small C- fibersfibers, some large A-delta fibers and small C- fibers
terminate in the laminae of dorsal hornterminate in the laminae of dorsal horn and in the substantiaand in the substantia
gelatinosagelatinosa
•• The laminaeThe laminae than transmit specific information (aboutthan transmit specific information (about
burned or crushed skin, about gentle pressure)burned or crushed skin, about gentle pressure) to 2ndto 2nd
afferent neuronafferent neuron
31. •• 22ndnd
afferent neuronsafferent neurons transmit the impulse from the substantiatransmit the impulse from the substantia
gelatinosa (SG) and laminaegelatinosa (SG) and laminae through the ventral and lateralthrough the ventral and lateral
hornhorn,,
crossing in the same or adjacent spinal segmentcrossing in the same or adjacent spinal segment ,, to the otherto the other
sideside
of the cordof the cord.. From there theFrom there the impulse is carried through theimpulse is carried through the
spinothalamic tractspinothalamic tract to the brain. Theto the brain. The two divisions oftwo divisions of
spinothalamic tract are known:spinothalamic tract are known:
1.1. the neospinothalamic tractthe neospinothalamic tract -- it carries information to the midit carries information to the mid
brain, thalamus and post central gyrus (where pain isbrain, thalamus and post central gyrus (where pain is
perceived)perceived)
2.2. the paleospinothalamic tractthe paleospinothalamic tract -- it carries information to theit carries information to the
reticular formation, pons, limbic system, and mid brainreticular formation, pons, limbic system, and mid brain
(more synapses to different structures of brain)(more synapses to different structures of brain)