2. CONTENTS
INTRODUCTION
DEFINITIONS
FAST PAIN AND SLOW PAIN
RECEPTORS ANS STIMULUS
PROCESS OF PAIN PHYSIOLOGY
PAIN PATHWAY
ANALGESIC PATHWAY
GATE CONTROL THEORY
VARIETIES OF PAIN
ASSESSMENT OF PAIN
MANAGEMENT OF PAIN
CONCLUSION
REFERENCES
3.
4. DEFINITIONS
According to the international association for the study of pain (IASP)
An unpleasant sensory and emotional experience associated with
actual or potential tissue damage, or described in terms of such
damage.
Monheims: “An unpleasant emotional experience usually initiated
by noxius stimulus and transmitted over a specialized neural network
to the CNSwhere it is interpreted as such.”
5.
6. Fast pain is due to the activity of mylinated
Aδ fibers and it is appreciated as sharp
bright and localized sensation.
Slow pain is due to activity of unmyelinated
C fibers and it is appreciated as dull aching
and more diffuse
7.
8. FAST PAIN is also described as sharp pain ,pricking
pain , electric pain.it is elicited by mechanical and
thermal type of stimuli.
SLOW PAIN is also called as, slow burning pain,aching
pain, throbbing pain,nauseous pain,chronic pain.
slow pain can be elicited by mechanical,thermal
and chemical stimuli.
9. PAIN RECEPTORS AND THEIR
STIMULATION
Pain Receptors (NOCICEPTORS) Are Free Nerve
Endings: The pain receptors in the skin and other
tissues are free nerve endings.
They are widespread in the superficial layers of
the skin as well as in certain internal tissues, such
as the periosteum , the arterial walls ,the joint
surfaces and the falx and tentorium of the brain.
10.
11. THREE TYPES OF STIMULI EXCITES PAIN RECEPTORS
Pain can be elicited by multiple type of stimuli they
are classified as:
MECHANICAL
THERMAL
CHEMICAL
In general fast pain is elicited by the mechanical and
thermal stimuli, whereas the slow pain is elicited by all
three types.
12.
13. NEUROTRANSMITTERS INVOLVED IN PAIN
SENSATION
Glutamate and substance P are neurotransmitters
secreted by the pain nerve endings. The A$ afferent fibers
which transmit impulses of fast pain secrete glutamate.
C type fibers which transmit impulses of slow pain secrete
substance P
14. PROCESS OF PAIN PHYSIOLOGY
Transduction
Transmission
Perception
Modulation
15.
16. TRANSDUCTION
Pain stimuli is converted to
electrical energy .This
electrical energy is known as
transduction .This stimulus
sends an impulse across a
peripheral nerve
fiber(nociceptor)
22. DUAL TRANSMISSION OF PAIN SIGNALS
INTO THE CENTRAL NERVOUS SYSTEM
Peripheral pain fibers- “Fast” and “slow” fibers.
The fast-sharp pain signals are elicited by either mechanical
or thermal pain stimuli; they are transmitted in the
peripheral nerves to the spinal cord by small type A$ fibers
at velocity between 6 to 30m/sec.
The slow chronic pain is transmitted by type c fibers at
velocity between 0.5 to 2m/sec.
25. THE DUAL PAIN PATHWAY IN THE
SPINAL CORD AND BRAIN STEM
On entering the spinal cord the pain signals take two
pathways to the brain ,
through:----
1.THE NEOSPINOTHALAMIC TRACT(for fast
pain)
2.THE PALEOSPINOTHALAMIC TRACT(for slow
pain)
26. NEOSPINOTHALAMIC PATHWAY
The fast TYPE A$ PAIN FIBERS transmit mainly
mechanical and acute thermal pain .
They terminate mainly in lamina 1(LAMINA MARGINALIS)
of the dorsal horns, and their excite second order
neurons of the neospinothalamic tract.
These gives rise to long fibers that cross immediately to
the opposite side of the cord through the anterior
commissure and then pass upward to the brain stem in
the anterolateral columns.
28. PALEOSPINOTHALAMIC PATHWAY
It transmits pain mainly from the peripheral slow-chronic
type c pain fibers,although it transmit some signals from
type from type A$ fibers as well.
In this pathway , the peripheral fibers terminate almost
entirely in Laminae 2 and 3 of the dorsal horns,which
together are called the SUBSTANTIA GELATINOSA.
31. ANALGESIA SYSTEM
Analgesia system means pain control system.
The body has its own analgesia system in brain which
provide short term relief from pain .It is also called
endogenous analgesia system
It is also called endogenous analgesia system.
The analgesia system has got its own pathway through
which it blocks the synaptic transmission of pain sensation
in spinal cord and thus attenuates the experience of pain.
Analgesic drugs such as opiods act through this system and
provide a controlled pain relief.
32. Analgesic pathway:-
(DESCENDING PAIN PATHWAY)
The analgesic pathway that interferes with pain
transmission is often considered as descending
pain pathway and fibers are the efferent fibers.
The ascending pain pathway being the afferent
fibers that transmit pain sensation to the brain.
33.
34. Role of analgesic pathway in inhibiting
pain transmission:-
1.fibers of analgesic pathway arise from frontal lobe of
cerebral cortex and hypothalamus.
2.These fibers terminate in the gray matter surrounding
the third ventricle and aqueduct of sylvius
(periaqueductal gray matter)
The fibers from here descend down to brainstem and
terminate on
a) Raphe magnus nucleus situated in
reticular formation of lower pons and upper medulla
b)Nuclus reticularis paragigantocellularis
situated in medulla
35. 4.The fibers from these reticular nuclei descends through
lateral white column of spinal cord and reach the
synapses of the neurons in afferent pain pathway situated
in anterior gray horn.
The synapses of the afferent pain pathway are between:
a)A$ type afferent fibers and neurons of marginal
nucleus
b) C type afferent fibers and neurons of substantia
gelatinosa of Rolando
5.At the synaptic level ,the analgesic fibers release the
neurotransmitters and inhibit the pain transmission before
relayed to brain.
36. Neurotransmitters of analgesic
pathway:-
The neurotransmitters released by the fibers of
analgesic pathway are serotonin and opiate
receptor substances namely encephalin, dinorphin
and endorphin.
39. GATE CONTROL THEORY
The psychologist Ronald Melzack and anatomist
Patrick Wall Gate proposed the gate control
theory for pain in 1965 to explain the pain
suppression.
According to them ,the pain stimuli transmitted
by afferent pain fibers are blocked by gate
mechanism located at the posterior gray horn of
spinal cord.If the gate is opened,pain is felt.If the
gate is closed ,pain is suppressed.
40.
41.
42. Mechanism of gate control at spinal
level:-
When pain stimulus is applied on any part of body,
besides pain receptors, the receptors of other
sensation such as touch are stimulated.
When all these impulses reach the spinal cord through
posterior nerve root , the fibers of touch sensation
send collarerals to the neurons of pain pathway i.e.
cells of marginal nucleus and substantia gelatinosa.
The impulses of touch sensation passing through these collaterals inhibit the
release of glutamate and substance P from the pain fibers.
43. The impulses of touch sensation passing through
these collaterals inhibit the release of glutamate
and substance P from the pain fibers.
This closes the gate and the pain transmission is
blocked.
44. Role of brain in gate control
mechanism:-
According to MELZACK and WALL Brain also
plays some important role in the gate
control system of spinal cord as follows-
1.If the gate in spinal cord are not closed,
the pain signals reach the thalamus through
lateral spinothalamic tract.
45. 2. The signals are processed in thalamus
and sent to sensory cortex
3.The perception of pain occurs in cortical
level in context of the person’s emotional
status and previous experiences
46. 4.The person responds to the pain based on the
integration of all these information in the brain
.Thus ,the brain determines the severity and extent
of pain
5.To minimize the severity and extent of pain ,
brain sends message back to spinal cord to close the
gate by releasing pain relievers such as opiate
peptides
6.Now the pain stimulus is blocked and the person
feels less pain
47. VARIETIES OF PAIN
ACUTE PAIN
CHRRONIC PAIN
CUTANEOUS PAIN
DEEP SOMATIC PAIN
VISCERAL PAIN
REFERRED PAIN
NEUROPATHIC PAIN
PHANTOM PAIN
48. ACUTE PAIN
Sudden onset
Lasts less than 3 to 6 months.
Temporary (disappears once stimulus is removed)
Can be somatic ,visceral or referred
49. CHRONIC PAIN
Persistent-Usually lasting more than six months
Cause unknown-may be due to neural stimulation
Physiological responses are less obvious especially
adaptation
Psychological responses may include depression
50. SOMATIC VS VISCERAL
SOMATIC PAIN-
Superficial :stimulation of receptors in
skin
Deep: stimulation of receptors in
muscles, joints and tendons
VISCERAL PAIN-
Pain from viscera is
unpleasant. It is poorly localized.
-Stimulation of receptors in internal organs
,abdomen ,and skeleton
-Visceral pain can be referred
51. Cause of visceral pain
1.Ischaemia
2.Chemical stimuli
3.Spasm of hollow organs
52. REFFERED PAIN
Referred pain is the pain that is perceived at a site
adjacent to or away from the site of origin.
The deep pain and some visceral pain are referred to
other areas. But the superficial pain is not referred.
53. Examples of referred pain
1.Cardiac pain is felt at the inner part of left arm
and left shoulder
2.Pain in ovary is referred to umbilicus
3.Pain from testis is felt in abdomen
4.Pain in diaphragm is referred to right shoulder
5.Pain in gallbladder is referred to epigastric
region
6.Renal pain is referred to loin
54.
55. ASSESSMENT OF PAIN
In the assessment of pain intensity ,rating scale
techniques are often used. The most commonly used
techniques are:-
NUMERICAL RATING SCALE
VISUAL ANALOGUE SCALE
McGILL PAIN QUESTIONNAIRE
BEHAVIOUR RATING SCALE
58. McGILL PAIN QUESTIONNAIRE
It is also known as McGILL pain index ,is a scale of rating
pain developed at McGILL University by Melzack and
Torgerson in 1971.
It is self report questionnaire that allows indivisual to give
their doctor a good description of the quality and
intensity of pain that they are experiencing.
It is very widely used questionnaire.
59. BEHAVIOUR RATING SCALE
For patient unable to provide a
self report of pain ,a score from 0
to 10 is assigned based on clinical
observation
64. ENDOGENOUS METHOD OF CONTROLLING PAIN INCLUDES:-
1. REMOVING THE CAUSE-
The original causative factor had been eliminated
2.BLOCKING THE PATHWAY OF PAIN IMPULSE-
This can be done by injecting drug possessing local analgesic
property in proximity to the nerve involved.
Thus preventing those particular fibers from conducting any
impulses centrally beyond that point.
65. 3.RAISING THE PAIN THRESOLD-
Raising pain threshold depends on the pharmacological
activity of drugs possessing analgesic properties.
These drugs raise pain threshold and alter pain reaction.
66. 4. PREVENTING PAIN REACTION BY CORTICAL DEPRESSION-
Eliminating pain by cortical depression is by the use of
general anesthesia.
5.USING PSYCHOMATIC METHOD-
This method affects both pain perception and pain reaction .
It includes audio analgesia.
69. REFERENCES
Monheims -local anesthesia and pain control in
dental practice.
GUYTON and HALL -Textbook of medical physiology.
K SEMBULINGAM –Essentials of medical physiology
INDU KHURANA- Textbook of human physiology
