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48 Somatic Sensations:
II. Pain, Headache,and Thermal Sensations
Dr. A.R. Jamshidi Fard2011
Types of Pain• Fast Pain
– sharp pain– pricking pain – acute pain – electric pain
• Slow Pain– Burning pain– Aching pain– Throbbing pain– Nauseous pain– Chronic pain
• Three Types of Stimuli Excite Pain Receptors:
» Mechanical» Thermal» ChemicalBradykinin, Serotonin, Histamine, Potassium, Ions, Acids, Acetylcholine,
Proteolytic enzymes. + ( Prostaglandins - Substance P)
Threshold of Thermal Stimuli
to Excite Pain Receptors
Other causes of Pain
Tissue DamageTissue IschemiaMuscle Spasm
Dual Pathways for Transmission of Pain Signals into the Central Nervous System
Capability of Pain Signals to Arouse Overall Brain Excitability
Pain Suppression (“Analgesia”) System in the Brain and Spinal Cord
periaqueaductalgray matterpons - medulla area seretonin releasing neuronenkephaline releasing neuronpainfiber
pre-synaptic inhibitionoccurs here via the release ofenkephaline, which blocksCa channels, subsequentlypreventing the release of acetylcholine+ +
ascending anteriolateralpain neuron going to the sensory cortex
spinal cord
free nerve ending
enkephaline releasing neuron
periaqueaductalgray matterpons - medulla area seretonin releasing neuronenkephaline releasing neuronpainfiber
pre-synaptic inhibitionoccurs here via the release ofenkephaline, which blocksCa channels, subsequentlypreventing the release of acetylcholine+ +
ascending anteriolateralpain neuron going to the sensory cortex
spinal cord
free nerve ending
enkephaline releasing neuron
periaqueaducta lgray m atter
pons - m edu lla
area
seretonin re leasing neuron
enkephaline re leasing neuron
pa infiber
pre -synaptic inh ib itionoccurs here v ia the re lease o fenkephaline , w h ich b locksC a channels, subsequentlypreventing the re lease o f acetylcholine
+ +
ascending an terio la tera lpa in neuron go ing to the sensory cortex
spina l cord
free nerve end ing
enkephaline re leasing neuron
Visceral Pain
True Visceral Pain- Ischemia - Chemical Stimuli- Spasm of a Hollow Viscus(cramps)- Overdistention of a Hollow Viscus
“Parietal Pain” Caused byVisceral Disease
Referred Pain
Some Clinical Abnormalities of Pain and Other Somatic Sensations
• Herpes Zoster (Shingles)
• Hyperalgesia
• Tic Douloureux
• Brown-Séquard Syndrome
Some Clinical Abnormalities of Pain and Other Somatic Sensations
• Herpes Zoster (Shingles)
• Hyperalgesia
• Tic Douloureux
• Brown-Séquard Syndrome
Some Clinical Abnormalities of Pain and Other Somatic Sensations
• Herpes Zoster (Shingles)
• Hyperalgesia
• Tic Douloureux
• Brown-Séquard Syndrome
Some Clinical Abnormalities of Pain and Other Somatic Sensations
• Herpes Zoster (Shingles)
• Hyperalgesia
• Tic Douloureux
• Brown-Séquard Syndrome
Headache• Headache of Intracranial Origin
– Meningitis - Low Cerebrospinal Fluid Pressure – Migraine – Alcohol –Constipation
• Extracranial Types of Headache– Muscle Spasm - Irritation of Nasal and Accessory Nasal Structures - Eye Disorders
Areas of the Head to Which Intracranial Headache Is Referred.
Inhibition of Pain Transmission by Simultaneous Tactile Sensory Signals
TENS
ranscutaneus
electrical
erve
timulation
Thermal Sensations
Receptors: - Cold receptors- Warmth receptors-Pain receptors “freezing cold” “burning hot”
Centers:-Reticular areas of the brain stem -Ventrobasal complex of the thalamus