creation date: 2026-02-02 17:48
tags: Anatomy & Physiology
Pain
Physiology of Pain Signals
Nociception is the transmission of noxious stimuli from peripherty to the brain to protect against harm.
Impulses to the brain can travel through Aδ fibres (for fast/sharp sensation) or C-fibres (for slow/dull sensation).
Types of Pain
Neuropathic
Characteristics
Damage or dysfunction of the neurvous system results in abnormal signals.
Pain is often described as:
- Burning
- Tingling
- Stabbing
- Shooting
Examples
Peripheral neuropathic pain:
- Postherpetic neuralgia
- Diabetic neuropathy
- Pain following chemoradiation
- Complex regional pain syndrome
Central neuropathic pain: - Pain following CVA
- Multiple sclerosis
- Spinal cord injuries
Nociceptive
Characteristics
Most common type of pain caused by tissue damage that trigger nerve endings. Pain receptors known as nociceptors send signal to brain.
Pain is typically:
- Acute
- Well-localized
- Described as aching or throbbing
- Subsides with healing
Examples
- Burns
- Contusions
- Sprains
- Postoperative pain
Musculoskeletal
Characteristics
Bone, joint, ligament, skeletal muscle, or tendon somatic pain.
Pain is typically:
- Localized
- Somatic nociceptive
- Worse with movement/use
- Improves with rest
Examples
- Back pain
- Myofascial pain
Inflammatory
Characteristics
Pain triggered by tissue damage or immune responses. Typically involves heightened sensitivity due to inflammatory mediators.
Pain is typically:
- Localized
- Throbbing/aching
- Worsens with movement
- Eases with rest or antinflammatory
- Associated with signs of inflammation (eg. warmth)
Examples
Autoimmune disorders:
- Rheumatoid arthritis
- Fibromyalgia
- Gout
Others: - Infection
- Cancer-related pain
Psychogenic
Characteristics
Pain isn’t associated with peripheral nociceptor activation but instead due to altered central processing in the brain.
Typically:
- Fluctuating in intensity/location
- Non-anatomical (diffuse/shifting)
- Disproportionate to any minor finding
- Worsens with emotional triggers
- Resistant to analgesics
Examples
Psychological, emotional, and behavioural factors:
- Tension headaches
- Functional abdominal pain
- Somatization disorder
Mechanical
Characteristics
Pain due to mechanical deformation or disruption of MSK tissues. Involves the activation of high-threshold mechanoreceptors.
Pain is typically:
- Sharply localized
- Worsens immediately with weight-bearing, movement, or palpation
- Improves with immobilization
- May be present at night
- Point tenderness, crepitus, or swelling may be present
- Lacks inflammatory signs
Examples
Structural distortion or compression of tissues:
- Expanding malignancies
- Benign tumours
- Advanced ascites
- Fractures
- Retained hardware pain