Prepared By RASHIDUL HASAN ROBEL B. PHARM (RU), M. PHARM (RU) REG. NO. A4968 PGD-HRM (BIM) EMBA (ULAB)

1. PREPARED BY
RASHIDUL HASAN ROBEL
B. PHARM (RU), M. PHARM (RU)
REG. NO. A4968
PGD-HRM (BIM)
EMBA (ULAB)
PAIN
TYPES &
PHYSIOLOGY

2. What is Pain?
The International Association for the Study of Pain
(IASP) defines Pain as an unpleasant sensory and
emotional experiences associated with actual or
potential tissue damage.
Pain is not just a physical sensation. It is influenced by
attitudes, beliefs, personality and social factors, and can
affect emotional and mental wellbeing.
People feel pain when a signal travels through nerve
fibers to the brain for interpretation.

3. TYPES OF PAIN
1. Acute vs Chronic
2. Nociceptive vs Neuropathic
3. Somatic vs Visceral
4. Somatogenic vs Psychogenic
5. Referred Pain

4. ACUTE PAIN
 Sudden onset
 Temporary
 High intensity
 Can be nociceptive,
somatic, visceral &
referred.
CHRONIC PAIN
 Persistent.
 Usually lasts for 6 months
or more.
 Low intensity.
 Can be neuropathic,
somatic & visceral.

5. NOCICEPTIVE PAIN
NEUROPATHIC PAIN
 It results from activation of nociceptors (pain
receptors).
 Well localized & sharp
 Usually worse with movement
 Can be acute or chronic
 e.g. trauma, post-operative pain etc.
 CENTRAL
 e.g. meningitis,
arachnoiditis,
migraine, post-
stroke pain etc.
 PERIPHERAL
 e.g. diabetic peripheral
neuropathy, post
herpetic neuralgia,
sciatic pain etc.
 Both are not well localized & sharp
 Usually chronic

6. SOMATIC PAIN
VISCERAL PAIN
 SUPERFICIAL
 Stimulation from
receptor in skin
 e.g. cutting
forearms, fingers,
toes etc.
 DEEP
 Stimulation from receptors
in muscles, joints, tendons
etc.
 e.g. osteoarthritis, bone
fracture (trauma)
 Stimulation of receptors in viscera (abdomen) &
internal organs of the body.
 e.g. pain from peptic ulcer, colitis, gallstones,
kidney stones, appendicitis etc.

7. SOMATOGENIC PAIN
 Pain that originates from actual physical cause.
 Acute/chronic or both.
 Somatic/visceral or both.
e.g. cutting finger, ischemic pain etc.
PSYCHOGENIC PAIN
 Imaginary pain, not caused by physical pathology.
 Chronic pain

8. REFERRED PAIN
Pain experienced at a point distant
to its point of origin.
Brain misinterprets signals as
coming from somatic region.
e.g. the pain associated with
Myocardial Infarction or heart
attack is commonly referred to the
left arm, neck & chest.
Distribution of
Referred Pain

9. These are actually & potentially tissue damaging event that may be
mechanical, chemical or thermal.
 It is a sensory receptor present in free nerve endings that responds to
potentially damaging stimuli by converting into electrical impulse.
 When cellular damage occurs, cell releases chemicals/mediators that
can stimulate nociceptors. Such as,
Prostaglandins
Histamine
Bradykinin
Leukotrienes
Substance P
Acetylcholine
Potassium ion etc.
NOCICEPTOR
NOXIOUS STIMULI

10. TYPES
OF
NOCICEPTORS
POLYMODAL
MECHANICAL
THERMAL
CHEMICAL
Responds to strong mechanical forces
such as cutting, crushing, pricking or
even firm pressure to the tissues.
Responds to excessive change of
temperature; above 45°C & below
17°C.
Responds to noxious chemical stimuli.
Responds to combination of
mechanical, thermal & chemical
noxious stimuli.

11. NOCICEPTORS LOCATION
 Mostly in skin
 Skeletal muscle
 Joint & tendons
 Periosteum (outer layer of bone)
 Viscera (abdomen, intestine etc.)

12. Sensory Nerve Fiber for Pain & Touch
‘Aβ’ Nerve Fibers ‘Aδ’ Nerve Fibers ‘C’ Nerve Fibers‘Aα’ Nerve Fibers
Size in diameter
Conduction speed
Myelin sheath
Stimuli/Impulse
13-20 μm 6-12 μm 1-5 μm 0.2-1.5 μm
80-120 m/s 35-90 m/s 5-40 m/s 0.5-2 m/s
Present Present Present Absent
Proprioception Touch Cold
Acute Pain
Heat
Chronic Pain

13. Neurons Involved in Pain Signaling Pathway
1st Order Neuron
 Conduct impulses from receptors of the skin and
from proprioceptors (receptors located in a join,
muscle or tendon) to the spinal cord or brain stem.
 Impulse carried by Aβ, Aδ & C nerve fibers.
 They synapse with second-order neurons.
 1st order neuron's cell bodes reside in ganglion
(dorsal root or cranial).
Cerebral
Cortex

14. Neurons Involved in Pain Signaling Pathway
2nd Order Neuron
 Carry signals from the spinal cord/brainstem to
thalamus.
 Cell body in the spinal cord or brainstem.
 They synapse with 1st & 3rd order neurons.
Cerebral
Cortex

15. Neurons Involved in Pain Signaling Pathway
3rd Order Neuron
Carry signals from the thalamus to the
primary sensory cerebral cortex.
They synapse with 2nd order neurons.
Cell body in the thalamus.
Cerebral
Cortex

16. PAIN PATHWAY PHASES
Transduction
Noxious stimuli are received by nociceptors & then converted
into electrical signal at sensory nerve ending (Aβ, Aδ & C nerve
fibers).
Transmission
It means propagation of the electrical signal from nerves to the
brain via spinothalamic tract.

17. Modulation
It means altering or blocking the pain signal as it travels through
spinal cord, medulla, pons, and midbrain to the cerebral cortex.
Perception
How the brain interprets the signal and produces pain.
Perception occurs when the nociceptive signal is received by the
involved cortexes within the brain.
PAIN PATHWAY PHASES

18. PAIN
PATHWAY
PHASES
Transduction
Transmission
Modulation &
Perception

19. Pain
Physiology
1st order
Neuron
Spinal Cord
Cerebral Cortex
Right Hand
Brain
Neurotransmitter
Substance-P
PG
Pain
Signaling
Pathway
&
Pain Perception
Aδ & C
nerve fibers

20. Touch
Signaling
Pathway
1st order neuron
2nd order neuron
3rd order neuron
touch on
right hand
Aβ nerve
fibers
Right Left
Cerebral
Cortex

21. Pain
Initiator
Neurotransmitters
Pain
Inhibitory
Neurotransmitters
Glutamate – Central
Substance P – Central
Bradykinin – Peripheral
Prostaglandin – Peripheral
Histamine – Peripheral
5-HT
Endorphins
Enkephalins
GABA
Glycine

22. PAIN SCALES
 A pain scale is a tool that doctors use to help assess a person’s pain.
 A person usually self-reports their pain using a specially designed
scale, sometimes with the help of a doctor, parent, or guardian.
 Pain scales may be used during admission to a hospital, during a
doctor visit, during physical activity, or after surgery.
 Doctors use the pain scale to better understand certain aspects of a
person’s pain. Some of these aspects are pain duration, severity, and
type.
 Pain scales can also help doctors make an accurate diagnosis, create
a treatment plan, and measure the effectiveness of treatment.

23. PAIN SCALES
Numeric Rating Scale
 Most commonly used pain scales in medicine.
 It takes less than a minute to complete.
 It only evaluates pain experienced in the last 24 hours.

24. Wong-Baker
Faces Pain Rating Scale
PAIN SCALES

25. PAIN SCALES
FLACC
Behavioral Pain Rating Scale
Assessment of Behavioral Score
0 : Relaxed and comfortable
1-3 : Mild discomfort
4-6 : Moderate pain
7-10 : Severe discomfort/pain
https://www1.health.gov.au/internet/publications/publishin
g.nsf/Content/triageqrg~triageqrg-pain~triageqrg-FLACC
It is used to assess pain for children
between 2 months and 7 years of age.

26. Cell Membrane Breakdown
Broken Phospholipid
Arachidonic Acid
Prostaglandin H2 Prostaglandin H2 Leukotriene A4
COX-1 COX-2 5-lipoxygenage
Phospholipase A2 Enzyme
PGE2
PGI2
TXA2
PGD2
PGE2
PGF2α
PGI2
Enzymatic Reaction
Leukotriene C4
Leukotriene D4
Leukotriene E4
Leukotriene B4

27. Enzyme Types Receptor Function
COX-1
derived
mediators
PGI2 IP
 Vasodilation
 Inhibit platelet aggregation
 Broncho-dilatation
PGE2
EP1
 Bronchoconstriction
 GI tract smooth muscle contraction
EP2
 Broncho-dilatation
 GI tract smooth muscle relaxation
 Vasodilatation
EP3
 ↓ Gastric acid secretion
 ↑ Gastric mucus secretion
 Uterus contraction (when pregnant)
 GI tract smooth muscle contraction
TXA2 TP
 Vasoconstriction
 Promote platelet aggregation
 Broncho-constriction

28. Enzyme Types Receptor Function
COX-2
derived
mediators
PGI2 IP
 Vasodilation
 Inhibit platelet aggregation
 Broncho-dilatation
PGE2 unspecified
 Pain
 Fever
 Inflammation
PGF2α FP
 Uterine contraction
 Broncho-constriction
PGD2 DP
 Produced by mast cells; recruits eosinophils
and basophils.
 Large amounts of PGD2 are found only in
the brain and in mast cells.
 Allergic diseases such as asthma

29. Enzyme Types Receptor Function
5-LOX
derived
mediators
LTB4
BLT1
BLT2
 Chemotaxis
 Recruits neutrophils
LTC4
CysLT1
CysLT2
 Broncho-constriction
 Increase mucous secretion
 Airway inflammation
 Asthma
 Increase vascular permeability
LTD4
LTE4