Flashcards in Nociception Deck (37):
What is pain?
An unpleasant sensory and emotional experience associated with actual or potential tissue damage.
What is nociception?
The neural process of detecting, coding and processing noxious stimuli - a purely physiological response.
What are the reasons pain is good?
It is an early cue to protect the body from serious harm.
It protects us by allowing us to sense damaging stimuli.
It teaches us to avoid harmful situations, and avoid similar danger in the future.
It forces us to rest an injured part of the body and allow time for tissue repair, this helps prevent infection.
It makes us toss and turn during sleep which prevents skeletal strain and bed sores.
What are the reasons pain is bad?
If it is chronic and serves no useful function e.g cancer pain, amputation pain, neuropathic pain, rheumatoid arthritis.
It persists even when the tissue injury is healed.
What are the three categories of pain based on its origin?
Somatic superficial - skin, a pinching, pinprick, cut resulting in a sharp brief pain.
Somatic deep - muscles, joints, deep skin layers, connective tissue, e.g muscle cramps and headaches, a burning, aching or itch that lasts longer than superficial pain.
Visceral - thoracic or abdominal internal organs, e.g appendicitis, billiary colic, peptic ulcers, dull aching pain or vague burning, poorly localised because pain receptors are less dense on viscera.
What are the characteristics of acute pain?
Resolved when injury is healed.
Recent, well-defined onset.
Expected to end within days or weeks.
Plays a vital warning function.
Forces rest so the injury can heal.
Examples are childbirth, sports injuries, skin abrasions/lacerations, muscle ligament/tendon damage, dental pain, post-operative pain.
What are the characteristics of chronic pain?
The pain persists and is not expected to resolve.
There is an ill-defined, gradual onset.
There is a long duration.
The pain is unpredictable and serves no biological function.
Resting doesn't improve the pain, and the pain persists even after the tissue injury is healed.
The pain is poorly treated.
Examples are lower back pain, inflammatory pain from rheumatoid arthritis, migraine, headache, cancer pain, neuropathic pain, pain from damage to brain or spinal cord, visceral pain.
Which pathway carries pain, temperature, crude touch?
Lateral spinothalamic = pain, temperature
Anterior spinothalamic = crude touch
What type of receptors do the first order neurones have?
Free nerve endings that are stimulated by noxious stimuli.
Which is the only part of the body with no nociceptors?
Where do the second order neurones run?
The decussate within two spinal segments of synapsing with the first order neurones and run contralaterally up the spinal cord, through the spinal lemniscus in the medulla and synapse with third order neurones in the thalamus.
What are the 5 types of nociceptors?
Sleeping/silent (activated by inflammation so produce pain once an injury has occurred)
What type of fibre are thermal and mechanical nociceptors?
A delta - first pain
What type of fibre are polymodal nociceptors?
C fibres - second pain
What is the difference between first pain and second pain?
First pain is rapid, sharp, has a short duration and is easily localised. It originates from thermal or mechanical nociceptors.
Second pain is slower onset, dull aching or burning, that has a long duration and is poorly localised. It originates from polymodal nociceptors.
What are the neurotransmitters released at the synapse between the nociceptors and second order neurones in the substantial gelatinosa?
Glutamate, Substance P.
What is the pathway that is like the spinothalamic tract but carries pain and temperature from the face and head via cranial nerves?
Spinal trigeminal tract of afferent first order neurones to the medulla, trigeminothalamic tract of second order neurones to the thalamus.
What is another term used to describe Brown-Sequard syndrome?
Dissociated sensory loss.
What causes referred pain?
Nociceptors from visceral and cutaneous tissues converging on the same second order neurone in the substantial gelatinosa, so visceral nociceptor activation can be perceived as a cutaneous sensation.
Where does the bladder refer pain?
Where do the ureters refer pain?
Lower abdomen and back
Where does the prostate refer pain?
Lower trunk and legs
What is phantom limb pain?
Sensation that a missing limb is still attached to the body, with chronic pain in the phantom.
What causes phantom limb pain?
Reorganisation of the somatosensory cortex so that the area previously dedicated to the limb is taken over by another body part.
What is Gate theory on the central modulation of pain?
Stimulation of Aalpha or Abeta fibres will stimulate an interneurone that inhibits the C fibre from stimulating the second order neurone, so the pain is suppressed. This is why rubbing an affected area stops it hurting.
Increased pain response to noxious stimuli.
What is allodynia?
A pain response to stimuli that wouldn't normally cause pain (Abeta afferents).
What is the difference between primary hyperalgesia and secondary hyperalgesia of an injury?
Primary hyperalgesia is in the site of an injury, secondary hyperalgesia is around the site of an injury.
What is fibromyalgia?
Widespread chronic pain, with allodynia and hyperalgesia.
What are four ways to pharmacologically manage pain?
NSAIDs e.g aspirin
Opioid receptor agonists e.g morphine
Local anaesthetics e.g lidocaine
What are 4 types of stimulation used to manage pain?
TENS (transcutaneous electrical nerve stimulation)
Gate theory - stimulate Aalpha and Abeta fibres
What is analgesia?
Absence of pain in response to normally painful stimuli.
What are some side effects of opioids?
Constipation, confusion, respiratory depression, addiction.
Which receptors in the brain do opioids target?
Mu, Kappa, Delta opioid receptors.
Which descending pathways decrease the release of nociceptive neurotransmitters glutamate and substance P?
Periaqueductal grey matter in the midbrain, raphe nucleus, affected by opioids.
What is naloxone?
Opioid receptor antagonist which reverses opioid overdose.