Clinical Pain
• pain that requires some form of medical treatment
• chronic pain affects more than one third of all people world wide everyday
• Most common reason people seek medical treatment
Common types of pain
• Acute pain
• Recurrent pain
• Chronic pain
• Hyperalgesia
• Opioid induced
• Long term potentiation
Measuring Pain
• We can’t objectively measure pain itself
• We can measure associated physiological changes
Electromyography ( EMG)
• asses the amount of muscle tension that pain suffers experience
Autonomic Arousal
• heart rate , breathing rate. , blood pressure
Measuring Pain
• we can observe patients pain behaviour
• Pain behavior scale
Target Behaviours
• sighing ,grimacing , rubbing , altered posture , altered gait
Children’s anxiety and pain scales ( CAPS)
Children’s Fear scale
• Capture dimensions of pain and fear in children
• We can ask people about their pain
Self report measures
• pain rating scales
• Numeric rating scale
Standardized Pain Iventories
• McGill pain questionnaire : sensory quality , affective quality , evaluative
quality of pain
The physiolgy of pain
Pain pathways
• afferent neurons
Free nerve endings
• sensory receptors that respond to temperature , pressure and painful
stimuli
• Interneurons
Noicicreceptors
• specialized neurons that respond to painful stimuli
Fast Nerve Fiers
• large myelinated nerve bers that transmit sharp and stinging pain
• Fast pain system servicing the skin and mucous membranes
Slow Nerve bers
• small , myelinated nerve bers that carry , dull aching pain
• Slow paikn system servicing all body tissues except the brain
Pain Pathways
• Pain process begins with neural signals from free nerve endings and are
routed to CNS
• Via three nerve bre
A Delta - large myelinated , fast and acute pain
C bre - small , unmyelinated , slow burning pain
A beta - large myelinated , inhibition of pain
Substantial Gelatinosa
• The dorsal region of the spinal cord where both fast and slow pain bers
synapse with sensory nerves on the way to the brain
Referred pain
• pain in an area of the body that is sensitive to pain but cause by disease or
injury in an area that has few pain receptors
The Neurohemistry of Pain
Substance P
• neurotransmitter secreted by pain bers in the spinal cord that stimulate
the transmission cells to send pain signals through to the brain
• Along with glutamate , continuously stimulates nerve endings at the site of
an injury and within the spinal cord , increasing pain messages
Enkephalins
• endogenous opioids found in nerve endings of cells in the CNS that bind to
Ovid receptors
• Regulates how much of the slow pain system’s message reaches the brain
Periaqueductal Gray ( PAG)
• region of the midbrain that plays an important role in the perception of pain
• Activates a descending neural pathway to close the pain gate
Anterior Cingulate Cortex ( ACC)
• Resembles a collar in surrounding the corpus callosum
• Plays a role in cognitive modulation of paikn
Endogenous Opiate Peptides
• Opiate - like substances naturally produced by the body
• Function as information messengers
The Pain Inhibiting System
• neural activity resulting from stimulation of the mid brain’s
periaqueductual gray .
• Activate inhibitory neurons in the spinal cord .
• These act directly on incoming slow nerve bers to block pain signals from
being relayed to the brain
Stress induced Analgesia
• Stress related increase in tolerance to pain , presumbly mediated by the
body’s endorphin system
• Endorphins ( body’s natural morphine )
Naloxone
• opioid antagonist that bins to opioid receptors in the body to block the
effects of natural opiates and pain killers
Genes and Pain
• Genes mediate anxiety and depression
• Genes affect indivual sensitivity to painful stimuli
• SCN9A: encodes instruction for sodium channels that relay on painful
sensations
• Come : one of several enzymes involved in metabolism of cateholamine
neurotransmitters
Gate Control Theory
• Neural “gate “ in the spinal cord regulates the experience of pain
Tranmisison cells - relay pain messages to the brain when the gate is open
Central control mechanism - descending neural pathway by which the brain
shuts the gate
Neuromtrix
• neural network integrates sensory information with emotional and
cognitive states
The experience of pain
Phantom limb pain
• following amputation of a limb , false pain sensation that appear to originate
in the missing limb
• Cramping , shooting , burning , crushing
• Underlying mechanism for this remain a mystery
Age and Pain
• progressive increase with age in reports of pain and a decrease in tolerance
to pain
• A normal consequence of aging
Gender and pain
• compared to men : women are more likely tho a doctor
• Women are more likely to report medical symptoms to a doctor
• Experience more frequent episodes of pain
• Report lower pain thresholds and less pain tolerance
• Gender differences apparent by adolesce
• Certain analgesics maybe more effect for women than for men
Socioeconomic Status and Stress
• people at lower socioeconomic levels have greater morbidity and morality
across many diseases
• More stressful life events
• More stressful environments
• Fewer psychological resources
• More vulnerable to the harmful effects of stress on health and physical
functioning
Culture and Ethinicty
• groups differ greatly in their norms for the degrees to which suffering
should be openly expressed and then form that pain behaviours should take
• Pain tolerance vs pain threshold
• Caution advised in the nding
Personality and mood state
• acute and chronic pain suffers show elevated scores on two personality
scales
• hysteria - tendency to exaggerate symptoms and use emotional behaviour
• hypochondriasis - tendency to be overly concerned about health and to
overreport body symptoms
• people who are anxious , worried , fearful and negative in outlook report
more pain
Types of patients
Dysfunctional patients
• report high levels of pain , feel they little control over their lives and are
extremely inactive
Interpersonally distressed patients
• Perdue little social support and feel other people in their lives don’t take
their pain seriously
Adaptive coppers
• report lower levels of pain and distress and continue to function at a high
level
Social Learning
• Social and cultural factors can in uence people’s experience of pain and
actually lead to the social construction of an illness
• Provide earlies model fo pain behaviour
• Determine future processing of pain experience
• Serve and adaptive function
• Operant conditioning model of pain
Treating pain
Medical Treatments
Analgesic
• drugs that are the main stay of pain control
Central acting
• narcotics
Peripherally acting
• non steroidal anti - in amaltorfy
Surgery
• destroys cells in the thalamus may alleviate some deep burning pain
Counter irritation
• Analgesia in which one pain is relived by creating another counter acting
stimulus
