pain mechanism 1 Flashcards
what is pain?
unpleasant phenomenon uniquely experienced by each individual
three systems that produce pain?
- sensory
- motivational
- cognitive
what does the sensory system do?
a discriminative system that processes info about strength, intensity, quality and spatial aspects of pain.
what does the motivational system do?
an affective system that determines the persons approach-avoidance behaviour
what does the cognitive system do?
it evaluates the individuals behaviour concerning their experience of pain.
what is somatogenic pain?
pain with a localised cause.
two types of somatogenic pain?
- nociceptive
2. neuropathic
what is psychogenic pain?
pain where there’s no physical cause - more to do with CNS process is disturbed
what is acute pain?
a protective mechanism that alerts the individual to a condition or experience that is immediately harmful to the body
what nervous system is associated with the perception of pain?
autonomic nervous system
what is chronic pain?
persistent or intermittent usually defined as lasting at least 3-6 months. (continues when it should not)
what decreases pain tolerance?
- with repeated exposure to pain,
- by fatigue, anger, boredom, apprehension
- sleep deprivation.
what increases pain tolerance?
- by alcohol consumption,
- medication, hypnosis,
- warmth, distracting activities
- strong beliefs or faith.
what effect does age have on pain threshold?
threshold increases with age
what is the gate theory of pain?
signals received and sent to the spinal cord (the gate), which decides whether to amplify the pain or attenuate it.
what type of afferent nociceptors do bone and visceral tissues have?
peptidergic C afferents
where are nociceptors localised to?
muscle skin and viscera
which are more and least myelinated out of A-beta, A-delta and C fibres?
A-beta= msot myelinated (thick myelin sheath) C= least myelinates (no myelin sheath) A-delata= thin myelin sheath
what are A-delta fibres useful for
crucial for fast signalling of injury
what fibres are 1st and 2nd pain detected by
1st pain is mainly detected by A-beta and delta whilst 2nd pain is detected by C fibres
what are TRP (VR) classes of nocieptors for
thermal sensitivitiy
what are TREK classes of nociceptors for
co-expressed with TRP and K+ channels for heat sensitivity. acitivity is reduced by heat
what are ASICS and DRASICS classes of nociceptors for
detect H+ and are cation selective
DRASICS also detect mechanical stimuli
what are MDEG classes of nociceptors for
SENSITIVE TO SODIUM CHANNELS
where are nociceptive inputs received in the spinal cord
at the superficial laminae i and II
where are mechanoreceptor afferents received in the spinal cord
at the superficial lamiae III to VI (3-6)
3 major types of superficial dorsal horn neurons
projection neurons
excitatory interneurons
inhibitory interneurons
what is the effect of acute pain on DH neurones
fast and slow depolarisation of DH neurones
what causes chronic pain
prolonged input from A-delta and C afferents activate NMDA
this triggers sensitation hyperglesia and allodynia
what does the nesopinothalamic tract do
carries information to the mid brain, thalamus and pons, limbic system, and mid brain ( more synapses to different strucures of brain)
what is the thalamus sensitive cortex used for in pain
percieves
describes
localises pain
what do the thalamus brainstem and reticular fomration do
identify dull longer-lasting, and diffuse pain
what do the reticular formation and limbic system do
control the emotional and affective response to pain
what does the efferent analgesic system do
inhbits afferent pain signals
how does the efferent analgesic system work
- pain afferent stimulates the neurons in periaquedectal gray
- then impulses are transmitted through the spinal cord to the dorsal horn
- here they inhibit or block transmission of nociceptive signals at the level of dorsal horn
