Anatomy and Physiology of pain 21.02.23 Flashcards
(44 cards)
What is the definition of pain?
Pain is an unpleasant sensory and emotional experience associated with, or resembling that associated with, actual or potential tissue damage
Why do we have pain?
Immediate pain warns of imminent tissue damage so we withdraw from the source of injury
- gives damaged tissues the best chance to heal
What is Nociception?
This describes the neural processes involved in producing the sensation of pain
What is an overview of the nociceptive pathway?
- Transduction in the periphery
- Through transmission to the dorsal horn of the spinal cord
- Then onto the brain
What is acute pain?
Pain for less than 12 weeks
What is chronic pain?
- Continuous pain lasting more than 12 weeks
- Pain that persists beyond the tissue healing
There is a sub classification into chronic non-cancer and cancer pain
What is Nociceptive pain?
Pain that arises from actual or threatened damage to non-neural tissue and is due to the activation of nociceptors
What is neuropathic pain?
Pain caused by a lesion or disease of the somatosensory nervous system
What is nociplastic pain?
pain that arises from altered nociception despite no clear evidence of actual or threatened tissue damage
What are 2 examples of neuropathic pain?
- Trigeminal neuralgia
- glossopharyngeal neuralgia
E.g stinging and burning
What is allodynia?
Pain due to a stimulus that does not normally provoke pain
What is dysesthesia?
An unpleasant or abnormal sensation, whether spontaneous or evoked
What is hyperalgesia?
Increased pain from a stimulus that normally provokes pain
What is hypoalgesia?
Diminished pain in response to a normally painful stimulus
What type of receptor detects pain stimulus?
Peripheral receptor will detect the relevant stimulus
What does the 1st order neuron do?
- Enters spinal cord through spinal nerve through the trigeminal nerve
- Enters ipsilateral to peripheral receptor
- Remains ipsilateral and synapses with 2nd order neuron
What does the 2nd order neuron do?
This crosses to the contralateral cord and ascends to the thalamus (the ‘relay’ station)
What does the 3rd order neuron do?
From the thalamus to the midbrain and higher cortical centres (somatosensory cortex)
What is transduction pathway with pain?
- This is turning a physical stimulus into an action potential
- Most are poly-modal (thermal/ chemical/ mechanical)
What are the primary afferent neurons?
Primary afferents are sensory neurons (axons or nerve fibres) in the peripheral nervous system that transduce information about mechanical, thermal, and chemical states of the body and transmit it to sites in the central nervous system.
What are nociceptors?
These are the free nerve endings of primary afferent neurons and can be:
- A fibres (fast acting): terminals release glutamate
- C fibres (slow acting): terminals release glutamate and substance P
Where are nociceptors found?
- In any area of the body that can sense pain either externally or internally
External: skin, cornea, mucosa
Internal: Viscera, joints, muscles. connective tissue
What ganglion do the cell bodies reside in?
Dorsal root ganglion - body
Trigeminal ganglion - face/ head/ neck
What type of fibres do the ganglions relay?
Sensory (afferent)
