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Chapter 10

Chapter 10 Notes.doc

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PSYC 328
Blaine Ditto

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PSYC328 Chapter 10 Notes WHAT IS THE SIGNIFICANCE OF PAIN? • Pain is critical as low-level feedback about functioning of body as a basis for making minor adjustments. • Pain makes person more likely to seek treatment. • Relationship between pain and the severity of an underlying problem can be weak. • Depression and anxiety worsen the experience of pain. • Pain is most common fear from illness/treatment. • Inadequate relief from pain is the most common reason for requests for euthanasia. • Chronic pain rates were highest among those with a lower level of education, Aboriginal, living in rural area, lower income and being unmarried (Southern Ontario) WHY IS PAIN DIFFICULT TO STUDY? Beecher: Found that ¼ war-wounded soldiers request morphine, civilians 80% request painkillers; thus meaning of pain sub- • stantially determines how it is experienced. • Culture, gender, coping styles, context all affect pain/difficulty in studying pain. Culture and Pain • No ethnic/racial differences in ability to discriminate pain. • Differences in culture; how soon report pain and reaction intensity differ. • Chinese students compared to European report lower pain tolerance for pain. • Cultural differences may derive from differences in cultural norms of pain expression and different pain mechanisms. Gender and Pain • Women show greater sensitivity to pain; can be a lot of variation in gender differences depending on the type of pain and when the pain is assessed. • Hormonal fluctuations in menstrual cycle known to influence pain perception in women. • Women more likely to report phantom limb pain. • May be due to ways men/women experience and emotionally process pain; women may respond to threatening stimuli with greater negative affect which in turn can amplify the response to pain. Coping Styles and Pain • Catastrophizing related to rumination, magnification, and feel helpless about how to manage pain; leads to more dramatic pain reports, also established as a risk factor for prolonged pain/disability; also leads people to estimate greater pain beha- viours displayed by others. • Resilience appears to be protective for pain catastrophizing; individual are able to bounce back by experiencing positive emotions. Measuring Pain • Barrier to treatment of pain is difficulty people have describing it objectively. Verbal Reports • One way to measure pain is to draw on large/informal vocabulary people have to describe pain. • McGill Pain Questionnaire (MPQ). • These things typically provide indications of the nature of pain, such as throbbing/shooting, as well as its intensity. • Measures developed also to address the psychosocial components of pain, such as fear or degree to which it has been cata- strophized (Pain Catastrophizing Scale). • Often use combinations of different measures. Pain Behaviour • Other measures focus on pain behaviour. • Pain behaviours are observable behaviours that arise as manifestations of chronic pain. • 4 Types: 1. Facial and audible expressions of distress. 2. Distortions in posture or gait. 3. Negative affect. 4. Avoidance of activity. • Analysis of pain behaviours provides a basis for assessing how pain has disrupted life. • Because pain behaviour is observable and measurable, the focus on pain behaviours has helped define the characteristics of different kinds of pain syndromes. • Pain now recognized as involving psychological, behavioural, and physiological components. Physiology of Pain • The experience of pain is a protective mechanism to make you aware of tissue damage. • Unlike other bodily sensations, the experience of pain is accompanied by motivational and behavioural responses; now re- cognized as important in its diagnosis and treatment. • 3 Types of Pain Perception: 1. Nociception: Pain perception that results from mechanical damage to the tissue of the body. 2. Thermal Damage: The experience of pain due to temperature exposure. 3. Polymodal Nociception: A general category referring to pain that triggers chemical reactions from tissue damage. Nociceptors in peripheral nerves first sense injury and in response relate chemical messengers, which are conducted to the • spinal cord, where they are passed directly to the reticular formation and thalamus and into the cerebral cortex. These areas then identify the site of injury and send messages back down spinal column, which lead to muscle contractions, • which can help block the pain and changes in other bodily functions (ex breathing). Peripheral Nerve Description Type of Pain Function Pain Gate Modula- Fibre tion A-Delta Small, myelinated Transmit first pain; Affects sensory as- Opens Gate sharp pain; rapidly pects of pain C Unmyelinated Transmit secondary Affects motivational Opens Gate dull or aching pain and affective ele- ments of pain A-Beta Large diameter, my- Transmit info about Concurrent stimula- Closes Gate elinated vibration and posi- tion can suppress tion pain transmitted by C fibres Theories of Pain • Before GCT, models suggested that pain resulted from transmission of pain signals from the site of injury to the brain, and that the amount of pain experienced was directly proportional to the amount of tissue damage. • Gate Control Theory: Ronald Melzack and Patrick Wall. • GCT: Challenged theory that pain resulted from a linear process from nerve stimulation to brain reception, and instead pro- posed that psychological factors play a significant role in the experience of pain. • GCT: There is a neural pain gate that can open and close to modulate pain signals to the brain. Modulation can occur at the spinal column level by the dorsal horn, through the activity of A-Delta and C-Fibres, which tend to open the gate. A-Beta fibres are involved in closing the gate. • GCT: However, signals descending from the brain can also modulate pain through central control trigger, a system of large- diameter, rapidly conducting fibres that activate cognitive processes. • GCT: According to this view of pain, physical/emotional/cognitive factors can make substantial contributions to the experi- ence of pain by either opening or closing the gate. Type of Factor Factors That Open The Gate Factors That Close The Gate Physical Extent of injury; Inappropriate activity Medication; Counter stimulation (e.g. level Massage, heat) Emotional Anxiety/Worry; Tension; Depression Positive emotions (e.g. Joy, interest); Re- laxation Cognitive Focusing on pain; Boredom Distraction or intense concentration on other things; Involvement and interest in life activities • GCT: Significance of psychological process in pain experience forced researchers to view pain and role of brain and other CNS regions in a different way. Ex, brain now viewed as actively selecting, filtering, and modulating signals rather than simply passively receiving them. Similarly, the dorsal horns, which were originally seen as being passive transmission sta- tions, were now viewed as dynamic sites involved in the inhibition and amplification of neural transmission. • Periaqueductal gray (a structure in the midbrain) also now known to lead to pain relief when stimulated. • Processes in the cerebral cortex are involved in cognitive judgments about pain, including evaluation of its meaning. • Affective dimension of pain made up of feelings of unpleasantness and negative emotions associated with future concerns; called secondary affect. • The overall experience of pain is a complex outcome of the interaction of these elements of the pain experience (nociceptive input, contextual information, exacerbated by strong emotions). • GCT: Can be used to explain several pain-related phenomena such as injury without pain. GCT Limitations: Cannot explain several types of chronic pain, including phantom limb pain (experiencing pain in a limb that • is not there). • Neuromatix Theory: Melzack proposed this to explain the above limitation. This theory states that there is a network of neur- ons that extends throughout areas of the brain to create the felt representation of a unified physical self, called the bod-self neuromatrix. Neuromatrix is genetically determined initially but open to changes from sensor inputs from experience. The neuromatrix generates nerve impulses that are continuously and cyclically processed and synthesized into a characteristic pattern called the neurosignature. Thus, for each pain experience a neurosignature is created that reflects the sensory/cog- nitive/emotional factors that are unique to that particular experience of pain. So the neurosignature (generated from body-self neuromatrix) and not sensor inputs that give rise to pain accordingly and explain phantom limb pain and other phenomena. Sensory inputs merely modulate that experience; they do not directly cause it. Neurochemical Bases of Pain and Its Inhibition • Brain can control the amount of pain an individual experiences by transmitting messages back down the spinal cord to block the transmission of pain signals. • DV Reynolds Study: Stimulation produced analgesia in mice. Lead to discovery of existence of endogenous opiod peptides. • Opiods are opiote-like substances produced in the body, that constitute a neurochemical based, internal pain regulation sys- tem. Opiods produced in many parts of the brain and glands of body, and project onto specific selective receptor sites in vari- ous parts of body. • Endogenous Opiod Peptides fall into 3 families: 1. Beta-endorphins, which produce peptides that project to the limbic system and brain stem, among other places. 2. Proenkephalin, which are peptides that have wide-spread neuronal, endocrine, and central nervous system distribu- tions. 3. Prodynorphins, found in the gut, the posterior pituitary, and the brain. • Particular factors must trigger the arousal of this system. • Stress might trigger it; acute stress reduces sensitivity to pain (stress-induced analgesia/SIA). • Physical activity might trigger the release as well; can enhance immune functioning. • Can be found in adrenal glands, pituitary gland, and hypothalamus. WHAT ARE THJE CLINICAL ISSUES IN PAIN MANAGEMENT? • WHO: Pain is a disease in its own right. • Traditional pain management systems: pharmacological, surgical, sensory techniques. • Increasingly psychologists involved; leading to biofeedback, relaxation, hypnosis, acupuncture, distraction, guided imagery, and other cognitive techniques. • Responsibility and commitment of patients to the pain treatment became central in the management of chronic pain. Acute and Chronic Pain • Two types of clinical pain; acute and chronic. • Acute typically results from specific injury that produces tissue damage; as such it is self-limiting and typically goes away when tissue damage is repaired; short in duration; defined as pain that goes on for 6 months or less. Types of Chronic Pain • 3 Types of Chronic Pain (Pain beginning with acute pain but does not decrease with treatment over time): 1. Chronic Benign 2. Recurrent Acute Pain 3. Chronic Progressive Pain • Chronic Benign: Persists for longer than 6 months and is relatively intractable to treatment. Pain varies in severity and may involve a number of muscle groups. Ex chronic low back and myofascial pain syndrome. • Recurrent Acute Pain: Involves a series of intermittent episodes of pain that are acute in character but chronic inasmuch as the condition persists for more than 6 months. Ex migraines, temporomandibular disorder, trigeminal neuralgia (spasms of face muscles). Chronic Progressive Pain: Persists longer than 6 months; increases with severity over time. Typically associated with malig- • nancies or degenerative disorders such as cancer or rheumatoid arthritis. 1/3 of Canadians suffer from chro
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