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PAIN
Dr Ghulam Mustafa
LO’s of the class
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Define pain
Properties of pain
Stimuli for pain
Receptors for Pain
Causes of pain
Types of pain w.r.t., Site
Fast vs Slow pain
Pain pathways
Body response to pain
• Unpleasant sensory experience that is
elicited by Noxious or nociceptive stimuli
Properties of pain
• Pain is a protective reflex
• Pain receptors are widely distributed
• Commonest symptom
• Earliest sign of Morbidity
• Non adaptive receptors
• Certain viscera insensitive to pain
– Brain
– Liver parenchyma
– Alveoli
Stimuli for pain
• Mechanical
• Thermal
– More than 45°C
• Chemical
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Bradykinin
Serotonin
Histamine
Potassium ions
Proteolytic enzymes
Receptors for Pain
1. Superficial skin layers
2. Internal tissues
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Periostium
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Joint surfaces
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Arterial walls
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Falx and tentorium
Causes of pain
1. Tissue damage
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Bradykinin
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Increased Potassium
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Increased Proteolytic enzymes
Rate of tissue damage α Pain intensity
2. Tissue Ischemia
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Lactic acid by Anerobic metabolism
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Bradykinin and proteolytic enzymes
Causes of pain
3 Muscle spasm
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Stimulate mechanosensitive pain receptors
– Compress the blood vessels and cause
ischemia
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Increases the rate of metabolism
Types of pain w.r.t., Site
1. Cutaneous pain
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Skin and subcutaneous tissues
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Accurately localized
2. Deep somatic pain
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Muscles, Tendons, Joints, Ligaments
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Mechanical forces, Ischemia, Chemicals
3. Visceral pain
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Poorly localize, radiates or refers
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Associated with ANS dysfunction
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Rigidity & tenderness nearby skeletal muscles
• Fast pain
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Sharp pain
Pricking pain
Acute pain
Electric pain
• Stimuli
– Mechanical
– Thermal
– Electrical
• Transmission
– A Delta Fibres
• Slow Pain
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Burning pain
Ache
Throbbing pain
Chronic pain
• Stimuli
– Chemical
• Transmission
– Type C fibres
• Transmission velocity
– 6 to 30 m/s
• Perception time
– 0.1 sec after
stimulation
• Body parts involved
– Usually skin
• Duration
– Short
• Neurotransmitter
– Glutamate
• Transmission velocity
– 0.5 to 2 m/s
• Perception time
– 1 sec or more
• Body parts involved
– Skin and deep
tissues
• Duration
– Long
• Neurotransmitter
– Substance P
• Localized
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Examples of stimuli
Needle prick
Skin cut
Burn
Electric shock
• Neo spino thalamic
tract
• Diffuse
• Tissue destruction
• Paleo spino thalamic
tract
• A Delta fibres
• Terminate in Lamina I
Lamina Marginalis
• Excite 2nd order
neurons
• Cross to opp side
thru Ant commissure
• Pass upward in
Anterolateral pathway
• Type C fibres
• Terminate in Lamina
II & III substantia
gelatinosa
• Signals thru short
fibre neurons
• Reach Lamina V
• Last neuron give rise
to long axons
• Cross to opp side
thru Ant commissure
• Pass upward in
Anterolateral pathway
• Neospinothalamic
• Few
– Reticular areas of
brain stem
• Most
– Thalamus
– Ventro basal
complex
– Post nuclear gp
• Somatosensory
cortex
• Paleo spino
thalamic
– Reticular areas of
medulla and pons
– Tectal area of
mesencephalon
– Peri aqueductal gray
region
• From brain stem
– Intra laminar nuclei
– V/L Nuclei of
thalamus
– Hypothalamus
Body response to pain
• Motor reaction:
– Withdrawl reflex
– Muscle rigidity
• Autonomic reaction
– Mild pain
• Posterior hypothalamic nuclei
–Increased sympathetic discharge
–Tachycardia
–Increased Blood pressure
• Severe pain
• Anterior hypothalamic nuclei
–Increased Para sympathetic discharge
–Bradycardia
–Decreased Blood pressure
• Emotional reactions
– Anxiety
– Depression
– Crying
LO’s were
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•
Define pain
Properties of pain
Stimuli for pain
Receptors for Pain
Causes of pain
Types of pain w.r.t., Site
Fast vs Slow pain
Pain pathways
Body response to pain