Define pain
Unpleasant sensory and emotional experience associated with actual or potential tissue damage
What is the epidemiology of pain
50% of patients experience moderate to severe post surgical pain 3-4.5% of the world suffer neuropathic pain
What is a synaptic transmission?
steps in the passage of a signal from one nerviest to another.
How do drugs affect the synaptic transmission
1) CA2+ block to prevent inflow (gabapentin) 2) block release of neurotransmitter 3) prevent neurotransmitter from binding with receptor
What is an active potential?
the movement of a signal along the axon of a nerve cel. channels are opened allowing flow of Na+ and Ca2+ into nerve cell. K+ close the channels returning to resting level
How are action potentials stoped?
nociceptive signals are blocked by blocking the action of the channels that control the movement of ons in the membranes.
How do local aesthetics work?
they stop Na+ channels from working, thus stop action potentials. (procaine)
What are the division and the definitions of the sensory systems?
1) Sensory system: transmits innocuous stimuli to touch pressurere warmth 2) Nociceptive: tissue damaged
Define Nociceptors:
free nerve ending that respond to stimuli that can cause tissue damage, or tissue damaged has been caused.
define transduction
the process of converting a stimuli into a nerve impulse
What causes a membrane potential to produce an action potential?
What is the transduction process at the periphery?
- chemical, mechanical, thermal stimuli
- changes in the receptor
- increase in ion flow across membrane (Na+ Ca2+)
- depolarisation of membrane potential
- action potential
What are transient receptor potential (TRP) channels?
TRP are receptor molecules that respond to strong stimuli
when mechanical, thermal and chemical stimuli produce a pain sentastion.
What are the characteristic of A type fibres
myelinated
action potential take 20m/sec
respond to mechanical and mechanothermal stimuli
what are the characteristic of C fibres?
Not myelinated
slow fibers 2m/s
polymodal fibres: respond to many modalities of stimuli
- chemical
- mechanical
- thermal
WHat is epicritic pain?
sharp fast pain felt as soon as the injury occured produced by A fibers
what is protopathic pain?
Secondary pain, dull aching and long-lasting. produced by C type fibers.
What is the trigeminal pain pathway?
Brings stimuli from the face about location intensity and quality of the pain. project the pain to the sensory cortex
What is the spinothalamic pain pathway?
Brings stimuli from the body about location intensity and quality of the pain. project the pain to the sensory cortex
Define nociceptive pain?
pain due to activation in cutanous, somatic and visceral structures. Tissue injury pain. physiological alarm system.
Define neuropathic pain
Pain arising as an indirect consequence of a lesion or disease affecting the somatosensory nervous system either periphery or CNS
Example
- alcoholism
- entrapment syndrome
- iatrogenic causes
- spinal cord trauma
- post-stroke pain
- MS
Define Acute pain
Occurs as a direct result of tissue damage or potential tissue damage.
it's a symptom
well defined onset, with clear pathology
acute serves to protect tissue damage
can be treated with drugs and manual techniques
Define chronic pain
Outlasts more than 3 to 6 months of healing time
the impairment is greater than expected from the physical findings of injury
pain occurs
**chronic pain does not serve a biological purpose
what are the three dimensions of pain?
- sensory discriminative
- motivational affective:
- cognitive evaluative
What is hyperalgesia?
increased pain sensitivity
What is allodynia
painfull response to stimuli that would normally be painfull
what is hypoalgesia
absence o pain in response to stimuli that would be painful
what is Dysesthesia?
an unpleasant abnormal sensation whether spontaneous or evoked
what is neurogenic pain?
pain caused by primary injury or dysfunction or disruption in PNS or CNS
what is a pain threshold?
the least experience of pain a subject can identify
