Week 6 - Lecture 1b - Pain

Question 1

mechanism of acute pain (5)

Answer 1

nociceptor receptors are activated by chemical, mechanical or thermal stimuli

pain impulses are then transmitted to the dorsal horn of the spinal cord (first order neurone)

contacts with second order neurones that cross to the opposite side (decussate) of the spinal cord

impulse ascend by the spinothalamic tract to the reticular activating system (RAS) and thalamus

the localisation and meaning of pain occur at the level of the somatosensory cortex

Question 2

transduction

Answer 2

signal initiation - stimulation of free nerve endings

transduction of noxious stimuli into a nerve impulse and depolarisation of the nerve stimulate the conduction of the sensory impulse

Question 3

transmission of nerve impulses from tissues to the CNS

Answer 3

occurs along type A (delta) and type C fibres

rapidly conducting type A fibres

• produce sensation of sharp , stinging, or pin-prick type local sensations
• induced by mechanical or thermal stimuli

impulses along type C fibres

• produce a dull ache or burning general response
• induced by chemical stimuli
• responses of the brain resulting from the transmission of impulses must be delivered back to the original site of stimulation

Question 4

modulation of pain

Answer 4

occurs during transmission of the impulse

• located in pathways of nervous system
• triggered by pain (tissue injury and or inflammation)
• excitatory neuromodulation
  
  • substance P, glutamine, somastostatin

-inhibiory neuromodulation
GABA, glycine, serotonin, norepinephrine
endorphins
enkephins

alter or inhibit the transmission of the pain impulse by slowing the release of nociceptive neurotransmitters

Question 5

The path of pain relief 6 steps

Answer 5

pain begins as a message received by nerve endings (burned fingers)
2. the release of neuromodulators sensitise the nerve endings (helping to transmit the pain from the site of injury toward the brain)

3. the pain signal travels as an electrochemical impulse along the length of the nerve to the dorsal horn on the spinal cord, thalamus and then to the cortex
4. pain relief starts with signals from the cortex
5. pain relief descend by way pf the spinal cord

6, chemicals such as endorphins are released in the dorsal horn to diminish the pain message

Question 6

Perception of the pain response

Answer 6

involves multiple parts of the brain ( the somatosensory cortex and the limbic systems)

perception is varied among individuals because of the influence of

• pain threshold : the intensity of the pain required to achieve a response
• perceptual dominance : the existence of pain at another location which is given more attention
• Pain tolerance : the degree to which pain is endured (duration or intensity) before initiating a response

autonomic response varies : tachycardia, tachypnoea, increased blood pressure, sweating, nausea and vomiting

Question 7

Pain classification

Answer 7

nociceptive pain : stimulus initiated outside of the nervous system
- involves specific receptors and pathways

non-nociceptive pain: originating within the nervous system

• neuropathic or neurogenic pain
• does not activate these receptors
• does not follow a typical transmission pattern

Question 8

acute pain

Answer 8

relatively brief sensation, usually less than three months duration
usually a response to a specific trauma - forms the basis for danger warnings and subsequent learning

Question 9

chronic pain

Answer 9

lasts more than three months - exists beyond the time or normal organic healing

pain begins to impair other function

• originate with acute pain
• develop for no apparent reason

Question 10

What Is visceral pain

Answer 10

stimulation of visceral organ receptors
felt as vague aching, gnawing, burning
associated with nausea, vomiting, hypotension, restlessness, shock
activated by tissue stretching, ischaemia, chemicals, muscle spasms

Question 11

what is referred pain

Answer 11

pain from one part of the body region perceived from a different region
visceral and somatic pain fibres travel in the same nerves
-brain cannot distinguish between the sources
-brain assumes stimulus from common (somatic) region
-number of receptors is greater superficially (skin)
-Brain accustomed to deal with superficial stimuli
- eg. left arm pain during heart attack

can be chronic *

Question 12

chronic pain

Answer 12

serves no purpose

poorly understood

imaging studies demonstrate that brain changes in individuals with chronic pain

• cognitive deficit
• decreased ability to cope with pain
• does not respond to usual therapy
• not possible to predict when an acute pain will become chronic

Question 13

cognitive behaviour interventions (nonpharmacologic)

Answer 13

relaxation - focus on lessening muscle tension
distraction - focus attention on stimuli not associated with pain
cognitive reappraisal - self distraction, focus on the positive aspects of the experience

imagery - use of imagination to develop a soothing mental picture

biofeedback - awareness of bodily function on a cognitive level

Question 14

Physical agents (non-pharmacologic

Answer 14

heat - increase in local circulation, reducing local ischemia, and nociceptive stimulation
modulation of pain
release of endogenous

cold - vasoconstriction to decrease swelling and stimulation of nociceptive pain fibres
reduced afferent activity

Question 15

other (non-pharmacologic )

Answer 15

transcutaneous electrical nerve stimulation

acupuncture (17)

Question 16

Pharmacologic

Answer 16

non narcotic analgesia

opioid analgesias

adjuvant analgesics (18)

Question 17

surgical intervention

Answer 17

severe chronic pain

inadequately controlled

especially effective if pain is unilateral

cut axons of the spinothalamic tract at the upper cervical level