Pain Flashcards
What is pain
it is an unpleasant sensory and emotional experience associate with actual or potential tissue damage, or described in terms of much damage
what does pain need
pain needs nociception- nociceptors- can occur without tissue damage
perception- sensory receptors (senses and somatic senses)
these relay information to our brains from- special senses- vision, hearing, balance, taste, smell
somatroy senses- tactile (touch, pressure, vibrations), thermal, proprioception, pain
transmission- sensory neurones- A delta fibres
nociceptors- small medium diameter/ myelinated, fast pain, response to thermal and mechanical stimulate, responses to acute pain- carry rapid and sharp pain, responsible for reflex response, information related to proprioception
transmission- sensory neurones- C fibres
nociceptors- small diameter/ non-myelinated, slow pain conduction, response to chemical, mechanical and thermal stimuli, slow burning type of pain
transmission- sensory neurones- a beta fibre
mechanoreceptors- large diameter/ myelinated, mechanical stimuli (heat or cold), allow rapid conduction, low activation threshold, usually response to light touch, transmit non painful information
pain pathway- stimulus
activates specific pain receptors called nociceptors (these are free nerve ending that respond to different stimuli, found in skin, joints etc.)
pain pathway- action potential
when these are stimulate an action potential is generated and A delta and C fibres transmit pain stimulus along the first order neuron to the spinal cord
pain pathway- nociceptors
the information from nociceptors then passes from the first to second order neuron via junction (use neurotransmitter
pain pathway- brain
pain signals travels to opposite side of spinal cord before ascending up to the brain, descending pathways- important in pain inhibition
how does pain move from PNS to CNS- 1
nociceptors are stimulated and send message along afferent nerve fibre (AKA first order neurone) to the spinal cord, A delta and C fibres transfer information to specific neurons in dorsal horn known as reclamae 1 and 2
how does pain move from PNS to CNS- 2
information crossed from first order neurone to second order neurone due to neurotransmitter glutenate and substance P that carry info over junction, the second order neurone then connects with the third order neurone
2 main pain pathways to brain
ascending and descending
2 main ascending pathways
spinothalamic tract and spinoreticular tract
2 main ascending pathways- spinothalamic
carries main pain signals, transmits info from dorsal horn via second order neurone, projectio to periaqueductal gray matter, terminates in thalamus where it connects with the third order neurone
2 main ascending pathways- spinoreticular
also ascending pathway in spinal cord, positioned closely to spinal flamed tract, ascends to reticular formation then the thalamus where it connects to the third order neurone, plays a role in memory and emotional pain
descending pathways
responsible for controlling and inhibiting information send along ascending pathway, neurones from periaqueductal gray go to nucleus raphe magnus they synapse here with the second and third order neurone ,, these descending pathways communicate at this junction- can stop transmission of messages
what are the important areas of descending pathway
important area- periaqueductal gray and nucleus raphe magnus
what is the role of descending pathway
they can inhibit pain transmission- by inhibiting the neurotransmitter, also stimulates neurone in substantia gelatinosa- when stimulated it releases an opioid- stops transmission of signals along second order neurone
registering pain- brain
receive the information, process information,execute an appropriate response
what determines the speed the information is transferred to the brain
it is dependant on the type of pain and the severity
registering pain- thalamus
sorting office, transfers information to the limbic system
registering pain- limbic system
emotional link, transfers info to somatosensory cortex, produces emotions that accompany pain, they can affect the intensity of pain
registering pain- somatosensory cortex
sensation explained as pain, this reacts to pain locating the source of injury, severity of pain, and plans a response, relays info to automatic response system
what does the automatic response system
these direct blood flow and nutrients to heal tissue and release pain suppressing chemicals that stops pain response
why do reflexes develop
reflex developed to deal with situations that need immediate response, initiates a reflex arc pathway
what is spinal reflex
integration occurs in the spinal cord (gray matter)
Simple spinal reflex response- sensory
sensory receptor (responds to a stimulus by producing a generator or receptor potential
Simple spinal reflex response- sensory neuro
sensory neuron axon conducts impulse from receptor to integrating centre
interneuron allow bypass to anterior horn of spinal cord where it can signal a motor signal to transfer to limb to be automatically moved
Simple spinal reflex response- integrating centre
one or more regions within the CNS that relay impulses from sensory to motor neurones
Simple spinal reflex response- motor neurones and effector
motor neurons- axon conducts impulses from integrating centre to effector, effector- muscle or gland that responds to motor nerve impulses
pain gate theory- ascending
ascending inhibition- activate A beta fibres, inhibit pain transmission- by rubbing it
pain gate theory- descending
descending inhibition- mind over matter, mid brain- axon descend to posterior horn of spinal cord and directly inhibit pain transmission
what is pain gate affected by- stimulus
if no stimulus gate is closed
what is pain gate affected by- A beta
if A beta are activated e.g. pressure, inhibitory interneuron is inhibiting P gate closed, substantia gelatinosa is excited and the gate is blocked/ closed to pain impulses which do not travel to the brain
what is pain gate affected by- A delta and C fibres
if A delta and C fibres activated, carry pain impulse to the gate in spinal cord, inhibitory interneuron is inhibited, the gate is open, and the impulses can carry the pain messenger to brain
what is pain gate affected by- unmodulated pain
activation of C fibres- info sent to junction connecting first order neurone and second order neuron and signals crossover with neurotransmitters
what is pain gate affected by- modulated pain
C fibres sent signals to same junction but this time an inhibitory interneuron is being activated because the A beta fibres are also sending information to the junction, which is crossing over at this junction and travelling up the second order neuron, this is reducing the transmission of pain from the C fibres
treatments to close pain gates- state of mind
the substantia gelatinosa at the pain gate can be affected by the person’s state of mind, e.g. anxiety causes impulses from the brain to open the gate and increase pain perception and being relaxed can activate the SG to close the gate
treatments to close pain gates- encephalins and endorphins
pain impulses reaching the brain cause messages to be sent to increase the release of endorphins/ encephallins from posterior horn and SG in the spinal cord and act to close the pain gate. levels of chemicals are also raised by exercise and acute trauma
treatments to close pain gates- central control
the brain can affect the gate as response to memories, past experiences and previous response strategies. all of these factors amy happen separately or at the same time
treatments to close pain gates- other
exercise, massage, electro therapy
pain types- acute and chronic
lasts a few months and chronic- persistent lasts for a prolonged period of time
pain types- nociceptor pain
pain caused by stimulation in soft tissue
pain types- neuropathic pain
causes by damage to nervous system- disorder of PNS and CNS- burning sensation
pain types- psychogenic pain
affected by psychological factors
what is chronic/ persistent pain
pain lasting beyond the time of healing of an injury and frequently there may not be any clearly identifiable cause, may be due to dysfunctional nociceptive system (e.g. hypersensitivity), some are due to ongoing tissue damage (e.g. arthritis, cancer)
what is peripheral sensation
increased sensitivity to an afferent nerve supply- modifies CNS so more pain is felt with less stimuli
what is a central sensitization
persistent nociceptive input from the knee drives the central neural changes within the spinal cord and brain resulting in pain amplification
what does central sensitization lead to
it leads to widespread hyperalgesia- due to changes to CNS, allymia-malfunction of descending pathways- more sensitive to pain at lightest of touches, chronic pain stage
example of central sensitization
pain starts in knee OA- from synovitis, subchondral bones, periosteum,
ascending C and A delta fibres activation to dorsal horn in spinal cord then to brain
