Pain Flashcards
Define pain.
An unpleasant sensory and emotional experience associated with actual or potential tissue damage.
Two types of pain?
Nociceptive
Neuropathic
Difference between acute and chronic pain?
Acute: less than 12 weeks
Chronic: more than 12 weeks, or pain that occurs after healing should have been completed
What is nociceptive pain?
Activation of nociceptors (pain receptors) found in skin, joints, bones, organ and NOT neural tissue.
What is neuropathic pain?
Pain due to lesion or dysfunction of neural tissue: nerves, spinal cord, brain
Name 2 types of axons that transmit pain from nociceptors.
C fibres
A delta fibres
What are characteristics of C fibres?
Small Unmyelinated Slow Mechano-, thermo-, chemo-sensitive Diffuse, dull, burning pain
What are characteristics of A delta fibres?
Large Myelinated Fast Mechano-sensitive Localised, sharp, stinging
What is an anaesthetic?
A drug that reversibly eliminates all sensation
By causing a block of conduction along nerve fibres.
Blocks Na+ channels preventing generation of action potentials
What is an analgesic?
Selectively suppress pain without affecting consciousness or other sensations.
Opioid analgesics are used in moderate to severe non-neuropathic pain
Acts on opioid receptor, diminishing its function
It releases histamine
What on earth is meant by periaqueductal grey?
It is grey matter located around the cerebral aqueduct
It is neurons that bear opioid receptors
When activated, the neurons inhibit release of substance P
The stimulus of the periaqueductal grey area can result in immediate analgesia.
What is substance P?
A neuropeptide that transmits pain to the CNS
Name the ascending pain pathways?
Spinothalamic tract
Spinoreticular tract
Are there mechanisms that act to inhibit pain transmission?
Yes
What is the Melzack & Wall gate control theory of pain?
Describes a process that inhibits pain transmission at the spinal cord level
Explains why the pain from banging your head is helped by rubbing it.
Rubbing activates A beta fibres with non-painful stimuli which inhibit pain signals transmitted by C fibres
