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