More Related Content
Similar to Pain physiology 2019 20- i
Similar to Pain physiology 2019 20- i (20)
Pain physiology 2019 20- i
- 3. Objectives
• Goal/Aim: To give the understanding of the
physiology of pain
• Specific Objectives: At the end of the lesson
student will be able to:
• Classify the types of pain.
• Describe the pain pathways
• Explain the mechanism of referred pain.
• List examples of referred pain
• Describe the Analgesia system.
© Prof .Dr. Rashid Mahmood
3
- 4. Lesson Contents
• Definition of Pain
• Types of Pain
• Pain Receptors
• Stimuli For Pain Receptors
• Mechanism of Stimulation of Pain Receptors
• Pain Pathways
• Analgesia System
• Methods for relieving Pain
• Referred Pain
• Visceral Pain
• Pain Insensitive Viscera
• Clinical Abnormalities of Pain
© Prof .Dr. Rashid Mahmood
4
- 5. MCQ1: Fibers involved in the
sensation of fast sharp pain are:
A. Alpha
B. A-delta
C. A-beta
D. C fibers
E. A gamma
© Prof .Dr. Rashid Mahmood
5
- 6. MCQ2: Fast pain is transmitted
at a velocity of about
A. 0.5-2m/sec
B. 2-4m/sec
C. 12-30m/sec
D. 40-60m/sec
E. 70-80m/sec
© Prof .Dr. Rashid Mahmood
6
- 7. MCQ3: First relay station of pain is:
A. Basal ganglia
B. Medulla
C. Pons
D. Spinal Cord
E. Thalamus
© Prof .Dr. Rashid Mahmood
7
- 8. MCQ4: The neurotransmitter of
fast pain is:
A. Bradykinin
B. Glutamate
C. Histamine
D. Prostaglandins
E. Substance – P
© Prof .Dr. Rashid Mahmood
8
- 9. © Prof .Dr. Rashid Mahmood
9
• Definition of Pain: Unpleasant sensation
caused by tissue damage.
Purpose:
Protective
Sherrington: “the physical adjunct of an imperative protective reflex”
International Association for the Study of Pain (IASP) Definition: “An
unpleasant sensory and emotional experience associated with actual
or potential tissue damage, or describe in terms of such damage”.
- 10. Types of Pain
1) Fast Pain:
Sharp, Pricking, Acute, Electric, Physiological
0.1 Sec
Skin
2) Slow Pain:
Burning, Aching, Throbbing, Nauseous,
Chronic, Pathological
0.1 Sec, Increase Slowly
Skin + Deeper Tissues
© Prof .Dr. Rashid Mahmood
10
- 11. © Prof .Dr. Rashid Mahmood
11
Nociception
• Process by which pain information is
carried from the peripheral sensory
receptors in the skin and viscera to the
cerebral cortex through network of
neuronal relays
- 12. © Prof .Dr. Rashid Mahmood
12
Pain Receptors (NOCICEPTORS)
• Free nerve ending
• Location:
Superficial layers of skin
Periosteum, arterial walls, joint surfaces, falx and
tentorium of cranial vault
Other deep tissues
• Non-Adapting
- 13. © Prof .Dr. Rashid Mahmood
13
Stimuli For NOCICEPTORS
Types of NOCICEPTORS
1. Mechanical NOCICEPTORS
2. Thermal NOCICEPTORS
1. Warmth Receptors
2. Cold Receptors
3. Chemically Sensitive NOCICEPTORS
Bradykinin, Serotonin, Histamine,
K+, Acids, Acetyl-Choline, Proteolytic enzymes.
4. Polymodal NOCICEPTORS
Combinations of these stimuli
- 14. © Prof .Dr. Rashid Mahmood
14
Mechanism of Stimulation of Pain
Receptors
1. Tissue Damage
1. Heat
2. Chemical Pain
2. Tissue Ischemia
1. Lactic Acid
2. Bradykinin
3. Proteolytic Enzymes
3. Muscle Spasm
1. Direct Stimulation
2. Ischemia
- 15. Chemical Mediators in response
to tissue damage
© Prof .Dr. Rashid Mahmood
15
Fig. 8-5, Ganong, 24th Edition
- 16. © Prof .Dr. Rashid Mahmood
16
Pain Pathways
• Two Pathways (Dual Pathway)
1. Fast-Sharp Pain Pathway
(Neospinothalamic Tract)
2. Slow-Chronic Pain Pathway
(Paleospinothalamic Tract)
- 18. © Prof .Dr. Rashid Mahmood
18
Peripheral Pain Fibers
(Fast & Slow Fibers)
• Fast-Sharp Pain
Signals:
Mechanical & Acute
Thermal Pain
Small type Aδ fibers
Myelinated
6-30 m/sec
• Slow-Chronic Pain
Signals:
Chemical Pain,
Persisting Mechanical
& Thermal Pain
Small type C fibers
Unmyelinated
0.5-2 m/sec
Double Pain
Sensation
- 19. Peripheral Pain Fibers (Fast &
Slow Fibers)
© Prof .Dr. Rashid Mahmood
19
Characteristic
Fast-Sharp Pain
Signals
Slow-Chronic
Pain Signals
Stimulus Type
Mechanical &
Acute Thermal
Pain
Chemical Pain,
Persisting Mechanical
& Thermal Pain
Fiber Type Small type Aδ fibers Small type C fibers
Myelination Myelinated Unmyelinated
Conduction Speed 6-30 m/sec 0.5-2 m/sec
- 20. © Prof .Dr. Rashid Mahmood
20
Carried by three neurons
• 1st,
• 2nd , and
• 3rd order neurons
- 21. © Prof .Dr. Rashid Mahmood
21
1st order neuron
• Fast-Sharp Pain Pathway
• (Neospinothalamic Tract)
Terminates in Lamina I
(Lamina Marginalis)
2nd order neurons start
here
Neuro-Transmitter:
• Glutamate
• Slow-Chronic Pain
Pathway
• (Paleospinothalamic Tract)
Terminates in Lamina II &
III (Substantia Gelatinosa)
Interneurons
Lamina V
2nd order neurons start
here
Neuro-Transmitters:
• Substance P: Slow action
• Glutamate: Immediate
action
Carries impulse
from nociceptor to spinal cord
Enters dorsal horn
Rises in Tract of Lissauer
- 22. © Prof .Dr. Rashid Mahmood
22
Transmission of both "fast-sharp" and "slow-
chronic" pain signals into and through the
spinal cord on their way to the brain.
1st order
neuron
- 23. © Prof .Dr. Rashid Mahmood
23
2nd order neuron
• Carries impulse from spinal cord to thalamus/Brain
Stem
• Fibers cross immediately to the opposite side
through Anterior Commisure
• Anterolateral Spinothalamic Tract
• Termination of fibers:
Fast-Sharp Pain Pathway:
Mainly: Thalamus (Ventro-
basal Complex)
A few fibers: Brain Stem
(reticular Formation)
Slow-Chronic Pain Pathway :
A few fibers: Thalamus
(Intralaminar Nuclei)
Mainly: Brain Stem
1. Reticular Nuclei of medulla,
Pons & Mesencephalon
2. Tectal area of Mesencephalon
3. Periaquedubtal grey region
- 25. © Prof .Dr. Rashid Mahmood
25
3rd order neuron
• Carries the impulse
from the thalamus to
the Primary Sensory
Cortex according to the
topographical
representation of the
body
• When the Primary
Sensory Cortex is
stimulated, the person
becomes aware of the
pain
- 26. ASSESSMENT Q.2
• Why a sudden painful sensation gives
double pain sensation?
© Prof .Dr. Rashid Mahmood
26
- 27. Take Home Points
• Pain is an unpleasant sensation caused by
tissue damage. It may be Fast Pain or Slow
Pain
• Pain Receptors, called NOCICEPTORS are
Free nerve ending & are Non-Adapting
• Stimuli For NOCICEPTORS may be
Mechanical, Thermal or Chemical
• Pain is transmitted to brain via Two Pathways
(Dual Pathway): Fast-Sharp Pain Pathway
(Neospinothalamic Tract) & Slow-Chronic
Pain Pathway (Paleospinothalamic Tract) 27
© Prof .Dr. Rashid Mahmood
- 28. Learning Resources
• Guyton and Hall (Text book of physiology),
13th Edition
• Ganong (Text book of physiology), 2`5th
Edition
• Masood Ahmed Khan (Neurophysiology
for Medical students, 3rd edition)
• Lecture Notes on Neurophysiology by
Prof. M. Tariq (2nd edition)Sherwood’s
Physiology, 9th Edition
© Prof .Dr. Rashid Mahmood
28
- 29. MCQ1: Fibers involved in the
sensation of fast sharp pain are:
A. Alpha
B. A-delta
C. A-beta
D. C fibers
E. A gamma
© Prof .Dr. Rashid Mahmood
29
B
- 30. MCQ2: Fast pain is transmitted
at a velocity of about
A. 0.5-2m/sec
B. 2-4m/sec
C. 12-30m/sec
D. 40-60m/sec
E. 70-80m/sec
© Prof .Dr. Rashid Mahmood
30
C
- 31. MCQ3: First relay station of pain is:
A. Basal ganglia
B. Medulla
C. Pons
D. Spinal Cord
E. Thalamus
© Prof .Dr. Rashid Mahmood
31
D
- 32. MCQ4: The neurotransmitter of
fast pain is:
A. Bradykinin
B. Glutamate
C. Histamine
D. Prostaglandins
E. Substance – P
© Prof .Dr. Rashid Mahmood
32
B