Lecture 35. Nociception and Pain Flashcards
What is the 1979 IASP definition of pain developed by Harold Merskey ?
An unpleasant sensory and emotional experience associated with actual or potential tissue damage, or described in terms of such damage
What is the new IASP definition of pain ?
An unpleasant sensory and emotional experience associated with, or resembling that associated with, actual or potential tissue damage
What can pain be influenced by ?
Biological, psychological and social factors
Does everyone feel pain the same ?
No it is personal
What are pain and nociception ?
Different phenomena
What can pain not be inferred solely by ?
Activity in sensory neurons
How can individuals learn the concept of pain ?
Through their life experience
What does the inability to communicate not negate ?
The possibility that human or non human experiences pain
What animal is often used as a model system to understand nociception ?
Apylsia Californica
What is acute pain essential for ?
Avoidance of injury
What is an avoidance tactic of acute pain ?
Withdrawal reflex
What is chronic pain ?
Pain that lasts 3-6 months after initial injury
What is chronic pain not beneficial for ?
Survival
What may chronic pain be associated with ?
Cortical plasticity
What does the nociceptor contain ?
Free nerve endings
What detects pain ?
The free nerve endings of the nociceptors
What are the types of fibres in the free nerve endings ?
- C fibres
- A delta fibres
- A beta fibres
Where do C fibres terminate ?
Laminae I and Laminae II
What is laminae II also known as ?
The substantia gelatinosa
What does the substantia gelatinosa do ?
Modulates sensory input
What are the afferent or sensory nerves ?
- Ia (A alpha)
- Ib (A alpha)
- II (A beta)
- III (A delta)
- IV (C)
Where is Ia found ?
Muscle spindle, primary endings
Where is Ib found ?
Golgi tendon organ
Where is II found ?
Muscle spindle, secondary endings
Where is III found ?
Muscle deep pressure endings
Where is IV found ?
Nociceptors (pain)
What are the efferent or motor ?
- A alpha
- A beta
- A gamma
Where is the A alpha found ?
Skeletal muscles
Where is A beta found ?
Muscles and spindles
Where is A gamma found ?
Muscle spindle
What does the peripheral immune system work with to protect the body ?
Immune system
What are the danger signal receptors ?
- TRP channels
- P2X channels
- Danger associated molecular pattern (DAMP)
What are transient receptive proteins (TRP) used for ?
Molecular mediators of nociception
What are the pain pathways ?
- Spinothalamic tract
- Spinoparabrachial tract
- Spinoreticular tract
- Spinomesencephalic tract
What are unmyelinated C fibres and small diameter A delta stimulated by ?
Injury
What do C fibres and small diameter A delta do when stimulated by injury ?
Convey impulses to transmission cells in the spinal cord
What do transmission cells receive input from ?
Large A beta fibres
What do transmission cells receive inhibition from ?
Interneurons
What influences inhibitory interneurons ?
Descending pathways
What do large diameter and small diameter fibres project to in the gate theory
The substantia gelatinosa and the first central transmission cells
What is inhibition from the substantia gelatinosa onto the afferent fibre terminals increased and decreased by ?
- Increased by L fibre activity
2. Decreased by S fibre activity
What is the brain region involved in nocebo responses ?
Hippocampus
What does direct electrical stimulation of the periaqueductal grey in a rodent produce ?
Analgesia
What is analgesia ?
Pain relief
What periaqueductal grey block ?
The nociceptor response
What are the critical components of descending pain modulation ?
- Periaqueductal grey
2. Rostroventral medulla
What does the periaqueductal grey coordinate ?
The defensive response to threat
What are some interventional treatments for neuropathic pain ?
- Spinal cord stimulation
- Cortical stimulation
- Deep brain stimulation
- Intrathecal drug delivery
What are the main component of phantom limb pain ?
Central changes
What is there some evidence for regarding phantom limb pain ?
Peripheral changes
In the brain what alters in amputees with chronic pain ?
Cortical representation
What is a possible therapy for phantom limb pain ?
Mirror therapy
