Pain Flashcards
5 examples of relevance for pain……GO
- Approx 10 million brits suffer pain- affecting their quality of life - causing them to have more days of work (British pain society, 2014)
- 8 Million people have chronic pain of at least moderate intensity.
- 6-8% of the population have severe pain that prevents some or most of their daily activities.
- It is a warning system telling us that something isn’t right
- The prevalence of pain doubles after the age of 65 but chronic pain can be experienced by anyone.
What is chronic pain?
- This is a persistent pain which continues after healing or is the result of ongoing damage.
- Chronic pain Is recognised as a long term condition in its own right.
What is acute pain?
- This relates to pain occurring during tissue damage and repair for example during sudden illness, surgery, trauma and burns 🥵.
- The pain typically improves with tissue healing.
What are the 5 types of pain?
1- Cutaneous pain - originates from the skin
2- Somatic pain - generated from deeper connective tissue - muscle, tendons and joints
3- Visceral pain - from internal organs
4- Referred pain - `perceived in an area away from the site of origin.
5- Neuropathic pain - resulting from the damage to i nerves or nerve endings.
What are the 3 classic physiological causes of pain?
1- Nociception- Pain caused by actual or potential injury
2- Inflammatory pain - Caused by the inflammatory process
3- Neuropathic pain - Caused by damage to nerves.
What are the 5 stages of nociceptive pain?
1- Transduction 2- Conduction 3- Transmission 4- Modulation 5- Perception
What is the nervous system comprised off?
Central= Brain and spinal cord Peripheral = Sensory ( afferent nerves) Motor = Efferent nerves
What do dendrites do in a neurone?
They percieve information from the body.
What does the cell body (stoma) do in a neurone?
Organises information.
What doors the axon do in the neurone?
It transmits information to other parts of the nervous system.
What is the space between 2 nerves meeting called?
Synapse
Pain is detected by specialised nerve endings what are these called?
- Nociceptors
- These are highly specialised primary sensory neurones mainly located in the skin, joints and walls of organs.
How do nociceptors work?
- They contain specialised protein receptors within their membrane.
- Once stimulated by noxious stimuli
- The protein receptors re- shape to create ion channels causing ions to flow through.
- This stimulates an action potential
- these nerve endings convert noxious stimuli into an electrical current (action potential)
What do mechanoreceptors do?
They respond to pinch and prick pain sensation
What do silent nociceptors do?
They respond to inflammation.
What does Polymodal mechanoheat do?
These are nociceptors that respond to heat and cold
Stage 1 of pain
What is TRANSDUCTION?
- A process where noxious stimuli are translated into electrical activity.
- It occurs at the sensory endings of nerves
- It refers to how the noxious (pain) stimuli causes the release of chemical mediators from damaged cells to cause an action potential
What are Free Nerve Endings (FNE)?
- These are afferent nerve endings meaning it brings info from the bodies periphery towards the brain.
- In the case of pain FNE are called nociceptors
- They function as cutaneous receptors and are essentially used to detect pain
What mediators are released following tissue injury?
- Prostaglandin
- Bradykinin
- Serotonin
- Potassium
- Histamine
- Substance P (The most famous pain mediator)
What do the pain mediators do?
- They produce reactions at the sites such as, vasoconstriction, vasodilation, increased permeability and inflammation.
- The consequence of mediator activity is the conversion of cell trauma into an electrical impulses. This istransduction
- Pain sensation requires sufficient chemical mediator action to stimulate nociceptors above a physiological point known as the ‘pain threshold’
- The bigger the stimulus the bigger the pain sensation.
What do the pain mediators prostaglandin and bradykinin do?
They reduce the threshold of pain receptors subsequently increasing the sensation of pain.
What does the pain mediator histamine do?
- They bind to receptors sites present on nociceptors directly stimulating receptors to begin the cause of pain.
How does lactic acid effect pain mediators?
- Lactic acid production lowers the pain threshold and both hydrogen and potassium ions released by damaged cells sensitise pain receptors making them more sensitive to low intensity stimuli.
- This means anyone producing Lactic acid can be in pain.
How is a pain impulse generated?
- There is an exchange of sodium and potassium ions (depolarisation and depolarisation) occurs at the cell membranes
- This results in an action potential and generation of a pain impulse (transduction)
Stage 2 of pain
What is CONDUCTION?
- This refers to to the collection of impulses throughout the sensory nervous system.
- Primary afferent neurone project the electrical pain impulse to the dorsal horn of the spinal cord ( this is where the peripheral nervous system and the central nervous system meet)
- Ascending relay neurones project this impulse from the spinal chord to the brain stem and thalamus via the thalamo- cortical projections
- Conduction is simply the electrical impulse moving through the nervous system
What is the process of conduction?
- Pain impulse is sent along the first order neurones to the dorsal horn located in the spinal cord.
- Here you have 2nd order neurones. The impulse the synapses between the two
- The 2nd order neurones relay the impulses via the sympathetic tract up to the brain which will synapse with the 3rd order neurones in the thalamus.
- From here it will process the info and various areas will perceive the pain
What are sensory afferent nerves?
- These nerves are relatively thick in size and allow the pain to be transferred very fast (5-30 m per second)
- These nerves make the body withdraw immediately from the painful and harmful stimulus.
- Produces sharp pain
What are C- fibres (also afferent nerves) and what do they do?
- They transmit impulses more slowly
- Produces a throbbing, burning pain, starts immediately following the the fast pain.
- They have very thin
- Pain impulses via C- fibres are transmitted slowly at a spread of less then 2m per second.
- The bodies response to this is immobilisation (guarding, spasm, or rigidity) so that healing can take place.
What is fast pain?
- Fast pain is associated with ‘A fibres’
- The sensation is experienced as sharp.
What is slow pain?
- This is a more dull burning sensation
- Occurs after a short if amount of time and can last days or weeks/
- Chronic pain is inappropriately processed by the body it can last several ,months.
- Slow pain is associated with C fibres
Where do C- fibres and delta fibres terminate?
- Terminate at the Dorsal horn of the spinal cord.
- Here there is a synaptic cleft between the terminal ends of these fibres (1st order neurones) and the nociceptive dorsal horn neurones (ADHN) (2nd order neurones).
- At this point the conduction ENDS and transmission begins
Stage 3 of pain
What is TRANSMISSION?
- In order for the pain to be transmitted across the synaptic cleft to the Nociceptive Dorsal Horn Neurones (NDHN) excitatory neurotransmitters are released which bind to specific receptors in the NDHN.
- After transmission from the spinal cord to the brain 🧠 stem via the spinothalmic and spinearabrachial pathway once again as an electrical impulse along the 2nd order neurones
- Spinothalmic = up the vertebrae
- Spinearabrachial = up the arm
What are the neurotransmitters involved in stage 3 of pain TRANSMISSION?
- Adenosine triphosphate (ATP)
- Glutamate
- Bradykinin
- Nitrous oxide
- Substance P (this is the most famous neurotransmitter)
Briefly explain what happens in the stages of pain up to stage 3.
- The electrical pain impulse is sent along the first order neurones to the dorsal horn at the spinal chord
- At this point is where the second order neurones are located and the impulse travels along the synapse between the 2
- The second order neurones then relay this impulse via the spinothalmic (vertebrae)tract up to the brain 🧠
- Here the impulse with travel along the synapse between the 2nd order neurones and 3rd order neurone in the thalamus.
- From here it will then process the information and various areas will perceive the pain
Stage 4 pain
What is MODULATION?
- Transmission of a painful stimuli is modified by a number of influences and this is known as MODULATION
- It is best considered and explained through the Gate control theory.
- E.G if you bump your head and put ice on it your head will stop hurting and will start to feel cold.
Explain the gate control theory in terms of MODULATION
- According to the Gate control theory, stimulation of the fibres that transmit non-painful stimuli can block the pain impulses at the gate of the dorsal horn.
For example - I’d A- beta fibres (touch receptors) are stimulated they dominate and close the gate.
- This ability to block pain impulses is the reason a person is prone to immediately grab and rub a stubbed toe.
- Desending fibres of the central nervous system have the ability to excite inhibitory neurones which then release endorphins, dynorphins which inhibit substance-P release.
-By locally coding the nerve supplying the injured tissue slows the rate of transmission of nerve impulses reducing the number of pain signals transmitted to the brain.
Explain the Phenomena of referred pain.
- The proximity of the skin and heart neurones is very close.
- Meaning the brain sometimes cant differentiate and process them separately.
- This is known as the Phenomena of referred pain
- For example if someone has a heart attack they can feel pain in the chest and all over the skin.
Stage 5 pain
What is PERCEPTION?
- This is the unique psychology of the individual and the conscious experience of pain.
- Pain signals are sent from the thalamus to the higher brain 🧠 centres including the anterior cingulate cortex and the somatosensory cortex where pain perception occurs.
What is the Limbic system?
- This is the area of the brain thought to influence the emotional response to pain.
- It deals with the feelings of pain, pleasure affection and anger
- The limbic system also evaluates the seriousness of pain and helps individuals remember why the pain occurred.
What is the stomatosensory cortex?
- This is the area of the brain that allows individuals to locate pain and describe it
What is the anterior cingulate cortex?
- A number of imaging studies show this region is activated during the perception of pain.
- It plays an important part in Chronic pain
What are the physiological consequences of pain?
- Due to the elevation in hormones and the sympathetic nervous response individuals in pain will experience:
- Increase in heart rate
- Increase in BP
- Both cardiac output and O2 consumption will also increase
- Pain instigates the bodies stress response increasing circulating catecholamine’s which subsequently causes vasoconstriction and impaired tissue perfusion.
- Can promote anxiety and sleeplessness
- Can lead to hyperglycaemia, lipolysis, and the breakdown of muscle mass.
- Pain can suppress natural killer cell activity critical for immune system function.
Please explain the relation to pain and vomiting.
- Low BP can make you vomit
- Chemoreceptors trigger zone at the base of the 4th ventricle has receptors including substance P and serotonin.
- Lots of receptors are involved in common pathways leading to vomiting. The final common pathway Substance P is involved
- If you release/ produce substance P you are at risk of vomiting because substance- P acts of the 4th ventricle of the brain.
- Vomiting can interfere with normal sodium potassium pump for normal electrical activity in the heart and brain.
- Excess vomit can cause cardiac arrest due to the failure of the heart.
- It can also cause seizures
How can pain be adequately managed?
- Pain cannot be adequately managed if its impact is not assessed regularly using valid and reliable tools. (British Paine society, 2018)
- In acute settings pain should be considered as the 5th vital sign and should be measured alongside temp, pulse, BP, and resps.
How can pain be monitored?
- Verbal- none, mild, moderate
- Numerical - 1-10
- Visual :) :(
- Behavioural- expressions, body language.
What is the PQRST pain assessment (Hudack, 1998)?
P= Precipitating Factors Q= Qualitative data R= Radiation S= Symptoms T= Time
