🔗 The Pain Transmission Process (a.k.a. Nociceptive Pathway)

Think of it as a 4-step relay race from the site of injury to the brain.

1. Transduction – Turning damage into signals

• When tissue is damaged (e.g., cut, burn, pressure), nociceptors (pain receptors) in the skin or organs detect it.

• These receptors convert the damage into electrical signals.

• Chemical messengers like prostaglandins, bradykinin, and substance P are released and sensitize the area (like sounding the alarm).

🧠 Pain signal is born.

2. Transmission – Sending the signal up

• The electrical signal travels along afferent nerve fibres:

  • A-delta fibres: fast, sharp pain (e.g., needle prick)

  • C fibres: slow, dull, aching pain (e.g., lingering burn)

• The signal enters the spinal cord (dorsal horn) and is relayed to the brainstem and thalamus via the spinothalamic tract.

🚦 Pain signal is on the highway to the brain.

3. Perception – Feeling the pain

• The thalamus acts as the brain’s relay station and sends the signal to:

  • Somatosensory cortex (what and where the pain is)

  • Limbic system (emotional response)

  • Prefrontal cortex (attention and interpretation)

• Now you’re consciously aware of pain — it hurts!

🧠 Pain becomes an experience.

4. Modulation – Turning the volume up or down

• The brain can amplify or dampen pain through descending pathways.

• It releases chemicals like endorphins, serotonin, and noradrenaline to inhibit the signal at the spinal level.

• This is where pain relief therapies (like medications, TENS, PBM, acupuncture, etc.) work — by enhancing this inhibition.

🔧 The brain adjusts the pain dial.

🐾 Bonus: What About Dogs?

This process is the same in dogs (and other mammals) — which is why pain relief and emotional safety are so important in training, handling, and rehab. Chronic or poorly managed pain can lead to behaviour changes, sensitisation, and fear-based responses.