Physiology of pain Flashcards
What is the definition of pain?
An unpleasant sensory and emotional experience, associated with actual tissue damage or described in terms of such damage
What are the 4 processes in the physiology of pain?
Transduction
Transmission
Modulation
Perception
What is transduction?
Translation of noxious stimulus into electrical activity at the peripheral nocicpeto
What is transmission?
Propagation of pain signal as nerve impulses through the nervous system
What is modulation?
Modification of pain transmission in the nervous system e.g. by inhibitory neurotransmitters like endogenous opioids
What is perception?
Conscious experience of pain. Causes physiological and behavioural responses
What is a nociceptor?
Specific primary sensory afferent neurones normally activated by intense noxious stimuli (e.g. mechanical, thermal or chemical)
First order neurones that relay info to second order neurones in CNS via chemical synaptic transmission
What neurotransmittors are involved in the nociceptive pathway?
Glutumate and pepties (substance P and neurokinin A)
Where is the cell body in the nociceptive pathway found?
Dorsal root ganglion
Where will you find second order neurones?
In the anterolateral system
They terminate in the thalamus
What is the spinothalamic tract?
Involved in pain perception (location, intensity)
What is the spinoreticular tract?
Involved in autonomic responses to pain, arousal, emotional respones and fear of pain
Where will the pain impulse go after the thalamus?
Sensory information is relayed (3rd order) to the primary sensory cortex
What kind of stimulus can activate a noiceptive receptor?
Mechanical
Thermal
Chemical
What are the different types of nocicpetors?
A-delta
C-fibres
What is an A-delta fibre?
Mechanical/ thermal nociceptors that are thinly myelinated.
Respond to noxious mechanical and thermal stimulus
Mediate first/ fast pain
What is a C-fibre?
Nociceptors that are unmyelinated
Collectively respond to all noxious stimulus
Polymodal
Mediate second/ slow pain
What type of pain with A-delta fibres produce?
Lancinating
Stabbing
Prickling
What type of pain will C-fibres produce?
Burning
Throbbing
Cramping
Aching
How can pain be classified?
Mechanisms (nociceptive, inflammatory, pathological)
Time course (acute, chronic, breakthrough)
Severity (mild, moderate, severe)
Source of origin (somatic or visceral)
What is nocicpetive pain?
Normal response to injury by noxious stimulus
Only provoked by an intense stimulus
Adaptive pain
What is inflammaory pain?
Activation of the immune system by tissue injury or infection
Variety of mediators released at the site of inflammation by leucocytes, vascular endothelium and tissue resident mast cells
Adaptive - promotrs repiar until healing occurs
What is hyperalgesia?
Heightened pain sensitivity to noxious stimuli
What is allodynia?
Pain sensitvity to innocuous stimulus
What causes neuropathic pain?
Damage to neural tissue
What are examples of neuropathic pain?
Compression neuropathies Peripheral neuropathies Central pain Postherpetic neuralgia Trigeminal neuralgia Phantom limb
What type of pain will neuropathic pain cause?
Burning
Shooting
Numbness
Pins and needles
What is dysfunctional pain?
No identifiable damage or inflammation
What are some examples of dysfunctional pain?
Fibromyalgia Irritable bowel syndrome Tension headache Temprormandibular joint disease Interstitial cysititis
What type of drugs can be used to treat dysfunctional pain?
Antidepressants
Anti-epileptics
What are the 2 different types of pathological pain?
Neuropathic
Dysfunctional
What is referred pain?
Pain developed in one part of the body felt in another structure far from the place of development
Why does referred pain occur?
Convergene of nociceptive visceral and skin afferents upon the same spinothalamic neurones at the same spinal level
Where can cardiac pain refer to?
Left arm and jaw
Where can gall bladder and liver pain refer to?
Right shoulder
Where can stomach/ pancreatic pain refer to?
Epigastric area
Where can appendix pain refer to?
Umbilical area
