pain physiology - transduction and transmission Flashcards
what is the definition of pain
an unpleasant sensory and emotional experience associated with actual or potential tissue damage
what is nociception
the neural process of encoding noxious stimuli `
what are examples of noxious stimuli
pressure
stretch
pinch
extreme temperature
what is transduction
free nerve endings of the PNS being stimulated to generate an action potential
what is transmission
transport of action potential from the PNS to the ANS
what are the three classifications of pain
nociceptive, nociplastic, neuropathic
what is nociceptive pain
pain that arises from actual or threatened damage to non neural tissue (pain due to activation of nociceptors)
what is nociplastic pain
pain that arises from altered pain reception despite no clear evidence of actual or threatened tissue damage causing the activation of nociceptors
what is neuropathic pain
pain caused by lesion or disease of the somatosensory nervous system
radicular pain is an example of what kind of pain
neuropathic pain
what is radicular pain
pain caused by irritation of the sensory root or dorsal root ganglion of a spinal nerve.
this irritation causes ectopic nerve impulses perceived as pain in the distribution (dermatome) of the axon
what is allodynia
pain due to stimulus that should not provoke pain
what is hyperalgesia
increased pain from a stimulus that normally provokes pain
allodynia can be present when a patient is experiencing
severe swelling
what is referred pain
pain felt in a part away from the cause of the pain
what is sensitisation
increased responsiveness of nociceptive neurons to their normal input
a response to a stimuli that would normally be considered sub-threshold
what is the classification of a first order neuron
unipolar
what is the classification of a second and third order neuron
multipolar
what is a nociceptor
free nerve endings (dendrites)
what stimuli do nociceptors respond to
mechanical - excessive pressure, stretch, pinch, sharp pricking
chemical - inflammatory mediators (h+) (protons)
thermal - extreme heat or cold
what determines the speed of action potential
axon diameter
degree of myelination
A delta type nerve fibres are responsible for transmitting
fast sharp and local pain
C type nerve fibres are responsible for transmitting
slow dull achey pain
are c type nerve fibres myelinated
no
are a delta nerve fibres myelinated
yes
what is the myelin sheath made up of in the PNS
schwann cells
the indentations in the myelin sheath are called
node of ranvier
what is the purpose of the nodes of ranvier
they allow for specialised ion exchange
between laminae in the dorsal horn there are
vast interconnections between laminae 1-7
the first order neuron is located in?
the dorsal root ganglion (input from body)
trigeminal ganglia (input from face)
the second order neuron is located in
the dorsal horn
where to neurons communicate
at chemical synapses using neurotransmitters
at the synaptic cleft, voltage cannot be transferred across the gap, what helps to bridge this gap
neurotransmitters
describe neuronal communication
neurons communicate at chemical synapses using neurotransmitters
binding of these neurotransmitters to the post synaptic neuron drives ionic flow - this initiates a post synaptic potential (a change in the electrical charge)
post synaptic potentials can either be excitatory (EPSP) or inhibitory (IPSP)
EPSPs will summate to reach the threshold and then
the neuron will fire
