Pain Flashcards
How does pain motivate us (3 different ways)
- Reflexively, we can immediately withdraw ourselves from it
- It is a disincentive for potentially self damaging behaviour (learning)
- It can show down behaviour and force us to rest and recover once damage has occurred
How is pain a reflex?
There are several modes in which pain acts - the simplest being a reflex arc (hand, hot stove)
How is pain a disincentive?
Linked to inhibitory mechanisms involving learning
Punishment and negative reinforcement
Punishment can involve adding a painful stimulus contingent on a behaviour (parent spanking, or electric shock for rats in learning experiments)
How can negative reinforcement be involved in a disincentive?
Can involve removing an aversive stimulus contingent on a response
(e.g immersing a burned hand in cold water to relieve the pain may increase this behaviour)
How can pain act as a recovery?
When recovering from injury, pain can be adaptive because it causes us to rest the injury
Rest allows the body to physiologically channel resources to the injured site
Rest is the often the best prescription
How are some psychological variability to pain involved
Tremendous differences in variability occur among individuals
Some with massive injuries report little pain while others with rival injury can be consumed by it
Exists despite the universal “hard wiring” for pain sensation and perception
Explain how pain is adaptive
We have been prepared by evolution for this
Pain can often be reported despite any obvious tissue damage or trauma
Pain is influenced by many factors besides the extent of tissue damage or pain stimulus
How does pain perception differ?
Often differs in context specific (child hurt in front of mom vs. friend)
Childbirth is very painful yet it can bring joy with excitement
Pain is consistent with the tissue damage that occurs at childbirth
What is the neural structures of pain
Pain has an innate physiological basis.
There are free nerve endings in the periphery which transmit information to the spinal cord
Information is carried up tracts to the midbrain and thalamus where it reaches conscious attention in the brain
What are receptors in the neural pain structure?
Not complex specific receptors that filter information
What are nocicpetors in the neural pain structure?
Free nerve endings that can respond to mechanical thermal (heat or cold) and various chemical stimuli off by tissue damage
Where can the free nerve endings be found?
-Skin, muscles
-Internal organs
-The membranes around bone
-The cornea of the eye
-The pulp of the teeth
What are fibers in pain neurons
Carry information to the spinal cord.
Comes in 2 types and are associated with different subjective sensations of pain
What are A-fibers in pain neurons
Thick, myelinated (fatty substance that covers some neural axons and increases the speed of conduction)
Extremely fast
What are pain neurons responsible for?
Thermal and mechanical nociceptors
Thought to mediate sharp, pricking pain sensations
What are C-fibers in pain neurons?
Thin, myelinated fibers that conduct information more slowely
Associated with nociceptors, and are believed to be responsible for dull, ongoing aching pain sensations
What are spinal cord tracts (Tracts to the brain)
Fibers enter the spinal cord through the dorsal roots and enter the dorsal horm where they synapse
What is a tract?
Group of neurons with a common origin and common destination
What are 3 of the most important tracts?
- Spinothalamic - spine to thalamus
- Spinoreticular - spine to brain stem
- Spinomesencephalic - spine to midbrain
Where does the spinothalamic tract lead (3 components)
Spinothalamic -> Thalamus -> Cortex (somatosensory and limbic cortex)
Controls emotional responses
Where does the spinoreticular tract lead (3 components)
Spinoreticular -> Reticular activating system (brain stem) -> arousal
Where does the spinomesencephalic tract lead (3 components)
Spinomesencephalic -> midbrain -> periaqueductal gray -> pain inhibition
What does the PAG and the hypothalamus do together? - exam question
The PAG links with the hypothalamus with connections sending information in both directions (up and down the spinal cord) and through the hypothalamus it connects with the limbic system
What did Gate control theory (Melzack) discover
Interneurons
What happens with interneurons synapse in pain inhibition
Interneurons synapse at the postsynaptic neurons of the ascending tracts of the spinal cord and may act in an inhibitory fashion
What does direct stimulation of the PAG do in pain stimulation
Direct stimulation of the PAG can lead to analgesia and does not reduce other tactile discrimination
What is PAG the origin off?
The PAG (where interneurons are released and allows suppression of pain) is the origin of several descending pathways that synapse on the interneurons and can modulate pain perception
What do touch sensors (A-beta fibers) do in the skin for the reduction in the perception of pain?
Touch sensors in the skin, when stimulated b y rubbing the skin, can disrupt the sensation of pain arising in a nearby structure such as a muscle
What can psychological variation in pain be also attributed to?
Psychological variation in pain can also be attributed to neurochemical changes that can occur during psychological stress and dull pain perception
What led to the discovery of endorphins?
Opioid drugs can allevate pain
This evolved a close receptors match from the opioid poppy as we have a neuron in our brain that can bind to the substance
How do opioids disrupt pain?
Activating descending modulating pathways from the PAG pathways with the interneurons
The active areas are the same as with electrical stimulation (PAG)
Where do endorphins and enephalins found?
Leu and met enkephalin and dynorphin can be found localized in the PAG and the dorsal horn of the spinal cord
Where are endorphins secreted?
Is actually secreted in the anterior pituitary and parts of the hypothalamus - they can be secreted into the ventricular system (PAG and SC)
What happens to endorphines under psychological stress
Under psychological stress, descending pathways - with their inhibitory interneurons and endorphins and enkephalins may act to suppress pain
How long does pain have to last in order to be considered chronic?
More than 6 months
What is chronic recurrent pain?
Does not get worse, but comes and goes with varying intensity
What is chronic intractable beneign pain?
Having pain all the time with varying intensity (back pain)
What is chronic progressive pain?
Is continuous and gradually gets worse (cancer)
What are some symptoms of chronic pain?
- Often irritable
-May lose sleep - Drained of energy
- May quit their job
- Social withdrawal
- Depression
Which gender has a lower pain tolerance?
Women tend to have a lower pain threshold and tolerance than men
What is a pain threshold?
The amount of time it takes for a painful stimulus to cause the subject to report pain
What is pain tolerance?
The amount of time a subject will endure a stimulus once it has become painful
Why is there thought to be differences in pain between each gender
May be due to social stereotypes
Social consequences of reporting pain factor in to reporting pain
How is pain measured? Can it even be measured?
Pain is very subjective
Numerous physiological measures that do not work well when assessing pain
X-rays, visual inspection, palpation and other imaging techniques can diagnose pathology, but cannot assess pain level
How do clinicians measure pain?
Clinicians assess pain-related behaviour such as verbalizing pain, medication requests, requesting help with or avoiding everyday activities
What are self reports of pain include?
- Interviews
- Rating scales
- Pain questionnaires
What is the McGill Pain Questionnaire?
Most widely used pain questionnaire
Allows for the description of pain on 3 broad dimensions
What are the 3 dimensions of pain in the McGill Pain Questionnaire?
Sensory - includes temporal, spatial, pressure and thermal properties
Affective - includes fear, tension, and autonomic properties
Evaluative - includes the subjective overall intensity of the pain experience
What does the pharmacological control includes?
The use of analegesics
What is a peripherally acting analgesics?
Peripherally acting analgesics inhibit the synthesis of chemicals that promote pain neural impulses
What are centrally acting analgesics - narcotics?
Bind to opiate receptors
These bind to and activate receptors normally activated by endorphins and enkephalins (the body’s endogenous system for pain killing)
This blocks the transmission of the pain signal
What do local anaesthetics do?
Blocks nerve impulses at the site of injection (muscle is also blocked)
What do tranquilizers do?
Slow down and decrease the amount of neural impulses
What does tranquillizers and local anesthetics both do to pain repression?
These do not directly affect the pain, but do relax patients and reduce anxiety about the pain (you just don’t care that it hurts)
How does surgery control pain as an alternative?
This is usually done in extreme cases and pain can easily find another route
How does acupuncture control pain as an alternative?
No one is sure how or why this works, but it seems to in many cases
How does physical therapy control pain as an alternative?
In maintaining flexibility and muscle tone, most muscular and joint pain will be reduced
How does transcutaneous electrical nerve stimulation (tens) control pain as an alternative?
This is similar to acupuncture except the skin is not punctured
How does massage control pain as an alternative?
This stimulates blood circulation and human touch is known to change the levels of many hormones (sex and pain)
How does relaxation control pain as an alternative?
Progressive muscle relaxation and focusing on pleasant things can help reduce pain and stress
How does distraction control pain as an alternative?
This is limited as the pain usually returns when the patient is no longer distracted (soldier or athlete)
How does biofeedback control pain as an alternative?
While monitoring biological activity from the body, patients can induce changes in bodily temperature, heart rate, muscle tension and other bodily functions that can change pain levels
