Pain Flashcards
• Pain is protective
– Brings into consciousness the awareness of tissue damage
• Pain doesn’t feel protective
– It is accompanied by motivational and behavioral responses:
• Crying,Fear, Withdrawal
Physiology of Pain
– Mechanical nociception • Mechanical damage to body tissue – Thermal nociception • Damage due to temperature exposure – Polymodal nociception • General category • Pain triggers chemical reactions from tissue damage
(pain perception) NOCICEPTION
conveys information about the senses to and from the brain[all motor nerves to skeletal muscles]
Somatic nervous system
convey info about the sense organs to the CNS
Afferent (sensory) neurons
convey info from CNS to muscles, organs, and glands
Efferent (motor) neurons
connect sensory to motor neurons
Interneurons
all motor nerves to smooth and cardiac muscles, galnds
autonomic system
Nociceptors in peripheral nerves first sense ____
injury
In response, release chemical messengers
which travel to spinal cord and brain ,____ neurons
afferent
Brain regions identify the site of the injury and
send messages back down spinal column, ____ neurons
efferent
• Leads to muscle contractions, helps block pain
• Changes in other bodily functions, such as
breathing
nociceptors
- Acts in spinal cord
* Involved in the transmission of pain impulses from peripheral receptors to the CNS
Substance P
- Acts in spinal cord
- Amplifies pain signal transmitted from spinal cord to brain
- Implicated in chronic pain
– Glutamate
- Released by tissue damage
* Prolong the experience of pain by continued stimulation of nociceptors
Bradykinin & prostaglandins
- Released by the immune system to signal the nervous system
- Produce responses such as decreased activity, increased fatigue, increased pain sensitivity
- May sensitize structures in the dorsal horn of the spinal cord to promote the development of chronic pain
Inflammatory cytokines
Head and neck pain is directly transmitted to
brain via the 12 ____ nerves
cranial
For the rest of the body, the peripheral nervous
system must send impulses to the brain via ___ ___
spinal cord
small, myelinated fibers that transmit sharp
pain
• Especially mechanical or thermal pain
• Regulate sensory aspects of pain by projecting onto areas of the
thalamus and sensory areas of the cortex
A-DELTA fibers
– large, myelinated fibers
• Conduct impulses 100x faster than C-fibers
• Easily stimulated
A-BETA fibers
– unmyelinated fibers transmit dull, aching pain
• >60% of all sensory afferents
• Require more stimulation
• Polymodal pain
• Regulate affective and motivational elements of pain by projecting onto thalamic, hypothalamic, and cortical areas
C-fibers
- Primary & secondary somatosensory cortices
- Anterior cingulated cortex (ACC)
- Thalamus
- Cerebellum
Brain areas involved in pain:
– The affective dimension of pain
– Feelings of unpleasantness and negative emotions
– Psychological and neural mechanismsinvolved
– Processed in the cerebral cortex are involved in
cognitive judgments about pain
Secondary Affect
Electrical stimulation of a rat’s brain produced a
high level of analgesia
– The rat did not feel the pain of surgery
• Conclusion: The brain can control the amount of
pain experienced
-substances like heroin or morphine,
but they are produced by the body
• These substances constitute an internal painregulation system
opioids
– Produce peptides that project to the limbic system,
brain stem, & elsewhere
Beta-endorphins
– Peptides that have widespread neuronal, endocrine, & CNS distributions
Proenkephalin
– Found in the gut, the posterior pituitary, & the brain
Prodynorphins
• Highly complex system (receptor sensitivity)
• Important in natural pain suppression
• Must be triggered
– Released by stress (Stress-Induced Analgesia)
• Suppress immune functioning
• Also implicated in cardiovascular control
• used for treating chronic pain
endogenous opioid peptides
• Typically results from a specific injury
– Wound or broken limb
• Disappears when damaged tissue is repaired
• goes on for six months or less
• During there is an urgent search for relief
acute pain
– Typically begins with an acute episode – Pain does not decrease with treatment – Pain does not decrease as time passes • Three types : – benign pain – recurrent pain – progressive pain
chronic pain
– Persists more than 6 months – Varies in severity – Any number of muscle groups – Relatively intractable to treatment – Ex: Chronic low back pain & myofacial pain
Chronic benign pain
– Intermittent episodes of acute pain
– Chronic because the condition lasts more than 6 months
– Ex: Migraine headaches & TMJMD
chronic recurrent pain
– Increases in severity over time – Persists longer than 6 months – Typically associated with malignancies or with degenerative disorders – Ex: Rheumatoid arthritis & cancer
Chronic progressive pain
Chronic pain may result from a predisposition to
respond to a bodily insult with a specified bodily
response
Prechronic pain – most crucial stage
– Time between acute and chronic pain
– Do you get better?
– Do you develop chronic pain?
- To soldiers, pain means, “I’m alive”
* To civilians it interrupts activities
Beecher’s study of WWII injuries
– Classical conditioning • Dentist office, hospital – Operant conditioning • Rewards for pain behaviors may promote development of chronic pain – Attention, sympathy, relief from normal responsibilities, disability compensation – Secondary gains – Personality – Psychopathology
individual diff of experience of pain
– Specific pain fibers and pain pathways exist, making the experience of pain virtually equal to the amount of tissue damage or injury
– Pain is a physical experience largely uninfluenced by psychological factors
– In reality, specificity is limited
– Pain is a complex, multidimensional phenomenon
Specificity Theory
– Structures in the spinal cord act as a gate for the sensory input that the brain interprets as pain
• Increase pain (open gate)
• Decrease pain (close gate)
– Gate located in substantia gelatinosa in the dorsal horn
• A-delta, A-beta, and C fibers regulate the “gate”
– Central control trigger consists of nerve impulses that descend from the brain and regulate the “gate”
• Periaqueductal gray matter supports this theory
• Affected by beliefs & prior experience
Gate Control Theory
– Extension of Gate Control Theory
– Stronger influence of the brain in pain perception
– The neuromatrix is a network of brain neurons that processes sensory information but can act even in the absence of sensory input (e.g., phantom limb)
Neuromatrix theory
- Rating scales
- Large informal vocabulary
- Questionnaires
Measuring Pain - Verbal Reports
• Multidimensional Pain Inventory
– Pain characteristics, interference with lives and
functioning, mood
Measuring Pain: Self-report
• Dysfunctional
– Higher pain, interference & distress, lower activity
• Interpersonally distressed
– Support persons not providing necessary support
• Adaptors
– Lower pain, interference & distress and higher functioning
• Repressors
– Report high pain & low activity but report low distress
Group patients into 4 categories for multidemensional pain inventory
• Beck Depression Inventory (BDI)
– Chronic pain patients present with a different profile than do depressed patients without pain
• Symptom Checklist 90-Revised (SCL-90-R)
– Can differentiate between pain patients and people pretending to have pain
Measuring Pain: Standardized Tests
\_\_\_ \_\_\_\_are behaviors that arise as manifestations of chronic pain – Distorted gait or posture – Facial/audible expressions of distress – Avoidance of activities
pain behaviors
– Measures muscle tension
– Little relationship with self-report pain
Electromyography (EMG)
Hyperventilation, blood flow in the temporal artery,
heart rate, hand surface temperature, surface
temperature, finger pulse volume, skin resistance level
Autonomic indices
• Acute Pain
– Advantages: signals injury and promotes healing
– Disadvantages: it hurts!
– Advantages outweigh disadvantages
• Chronic Pain
– No Advantages
– Syndromes of pain based on symptoms
– Recurrent attacks of pain that vary in intensity, frequency, & duration
• Symptoms: loss of appetite, nausea, vomiting, & exaggerated sensitivity to light and sound
• 30-50yrs of age
migraine headaches
– Muscular in origin, accompanied by sustained
contractions of the muscles of the neck, shoulders, scalp, and face
– Includes mechanisms in CNS
• Symptoms: gradual onset; sensations of tightness; constriction or pressure; highly variable intensity, frequency,
and duration; dull, steady ache on both sides of head
– 40% of US population affected
Tension headaches
– Severe headache that occurs in daily or nearly daily clusters
– Symptoms similar to migraines but much briefer, rarely last longer than 2 hours
– Localized on one side of the head; the eye on the other side often becomes bloodshot and waters
– Men > women at 10:1
Cluster Headache
• Very common; 80% of people in US
• Most people recover
• Those who do not recover develop chronic pain
problems
• Substantial cost: > $90 billion a year
• Causes:
– Most frequent: injury or stress resulting in
musculoskeletal, ligament, and neurological in the lower back
– Infections, degenerative diseases, cancer, stress & psychosocial factors
Low Back Pain
• Experience of chronic pain in the absence of a
body part
• Amputation removes the nerves that produce the impulses leading to the experience of pain but not the sensations
• Not limited to limbs, also found with breasts and teeth
• Severity and frequency varies
• Decreases over time
• Cause is debated but evidence supports the
Neuromatrix Theory
Phantom Limb Pain
– Rheumatoid arthritis
• Autoimmune disease characterized by swelling & inflammation of joints, cartilage, bone, & tendons
• Can occur at any age & more frequent in women
– Osteoarthritis
• Progressive inflammation of joints; dull ache
• Most common form; especially among elderly
athiritis pain
