PAIN Flashcards
Give 3 aspects of the definition of pain
Sensory, Emotional, Homeostatic response.
Define Pain In terms of the Sensory component.
PAIN = A sensation evoked by injury
Define Pain in terms of the Emotional component
PAIN = An unpleasant and aversive experience (affective)
Outline the possible purposes of pain.
- Response to potential tissue damage
- Avoidance/defence
- Warning/Protection
- Rest
- LEARNING
Give an example of how Pain can be caused directly by injury
David Lawrence (cricket player), knee-cap split, in obvious pain, last time he played.
Give an example of where there is an absence of Pain following injury
Manteo MItchell (sprinter) broke his left fibula halfway through his run of relay but continued without pain.
What was Descartes definition of Pain?
Fast moving particles of fire that pass along the nerve filament and reach the brain
What are Nociceptors?
The sensory receptor that transduce painful stimuli to electrical signals and transmit them to higher centres in the CNS
What is Microneurography?
a Neurophysiological method to visualise and record traffic of impulses in peripheral nerves of awake human subjects. Its used to record nociceptor activity
With what type of Nociceptor is pain sensation transmitted>
Unmyelinated C fibers (primarily) and lightly myelinated A-delta fibres.
What are the main features of C fibres?
- Are polymodal; respond to noxious mechanical, heat and even chemical (histamine)
- Have small receptive fields
- Have slow conduction velocities 0.5-1.5m/s
What are the TRP family with regards to sensation and nociception?
Transient Receptor Potential Cation Channels. They open in the membrane of the C fibre in response to specific modalities
What are TRPV1, TRPV2 and TRPA1 responsible for in the C-fibre?
TRPV1 = detection of temperature provides sensation of scalding heat (43 degrees up). Responds also to Capsaicin (in pepper) TRPV2 = detection of higher temps (52 degrees up) TRPA1 = mechanical stress sensor.
What is the sodium channel expressed by nociceptors?
Nav1.7 which is encoded by the gene SCN9A. It amplifies small depolarisations and is a threshold channel that regulates excitability. It is required for pain sensation
Name the three pain disorders caused by mutations of the SCN9A gene.
- Primary Erythromelalgia (PE)
- Paroxysmal Extreme Pain Disorder(PEPD)
- Congenital Insensitivity to Pain (CIP)
Outline the symptoms of PE
Severe burning pain and skin redness in extremities triggered by heat, pressure and exertion Inheritance is Dominant. Nav1.7 function is increased
Outline the symptoms PEPD
Pain in mandibular, ocular and rectal areas. Nav1.7 function is increased.
Outline the symptoms of CIP
Insensitivity to Pain, otherwise the individual is normal. Nav1.7 function is absent
Name the 7 factors that affect an individuals perception of pain.
- Site of origin
- Duration
- Context
- Cultural Background
- Past History
- Expectation
- Mood (depression)
What 2 principles show that Nociceptive input is modified by CNS?
Pain without injury: back pain, migraine. neuropathic pain
Injury without pain.
What is Neuropathic Pain?
The pain following a peripheral nerve lesion produces one of the worst pains.
Outline the importance of the Dorsal Horn
It is the site of first synapse for nociceptive fibres it’s the site of integration and modulation of info.
Outline the important features of the Gate Theory
- nociceptive signal is modified at the Dorsal Horn
- Low Threshold A-Beta mechanoreceptor input inhibit nociceptor input
- Descending info from brain can alter nociceptive signal.
What is the difference between Pain and Nociception?
Nociception is the processing of signals from nociceptors but Pain is the subjective experience in the brain
