Class Notes (806,888)
Canada (492,503)
Psychology (3,452)
PSY333H1 (68)
Lecture 7

Lecture 7.docx

10 Pages
Unlock Document

University of Toronto St. George
Nevena Simic

LECTURE 7 – Pain  Final exam chapter 10-12  Pain can cause unconscious response (example: putting your hand on a hot stove and you automatically take it off) Significance Of Pain  Pain = symptom of chief concern to patients -Leads them to seek medical attention  Pain often considered of secondary importance to MD  Physicians are interested in what’s causing the pain because they want to find out the underlying cause of symptom  Patients fear pain in illness and treatment most -Fearing that they can’t relieve suffering  inc anxiety -Most common reason for euthanasia  $4 billion is spend annually in Canada on over-the- counter pain meds Why Do We Feel Pain?  Pain is adaptive -Tells us to avoid behaviors that may hurt us -Forces us to rest & recover after an injury  Can be reflexive & unconscious -Hot stove burner  Can be used as a learning mechanism -Electric shock for rats -Spanking for children Pain As An Inhibitory Mechanism  Operant Conditioning -Learning based on consequences -Positive = add; Negative = take away  Reinforcement: consequence increases likelihood of behavior in the future -Positive Reinforcement - application of a desirable stimulus (reward; candy) -Negative Reinforcement - removal of a negative stimulus (don't have to do a chore if good)  Punishment: consequence decrease likelihood of behavior in the future -Positive Punishment - application of aversive stimulus (spanking) -Negative Punishment - take away something good (tv time)  Using pain to learn  Positive Punishment and Negative Reinforcement involve aversive, potentially painful stimuli -Electric shock -Spanking -Soothing burns How Do We Know When Someone Is In Pain?  Pain behaviors are behaviors that occur in response to pain such as 1) Facial & audible expressions of distress 2) Distortions in posture or gain 3) Negative affect 4) Avoidance of activity What Is Pain: Elusive Nature  Pain is a subjective experience -Degree to which pain is felt and how incapacitating it is depends on how it is interpreted  Heavily influenced by context in which it is experienced -Beecher’s example of soldiers versus civilians o 25% wounded soldiers ask for morphine versus 80% of civilians after surgery o What is pain for the soldier? For the patient?  Stereotype that soldiers are supposed to be strong and manly and not feel pain  Elevation of opioid  For soldiers the symptom of pain meant they survived but for the civilian it was a life threatening as opposed to life affirming -Sports injury continue to play o SNS arousal diminishes pain sensitivity What Is Pain?  Can refer to many different sensation -Sharp pain: cut yourself on glass, step on nail -Dull ache: lower back pain, migraine, headaches -Blistering: sunburn, burn on hand -Small but irritating: cut your finger with paper cut  Acute Pain -Intense -Short-lived -Disappears as injury heals -<6 months  Chronic Pain -Begins as acute pain -Doesn't go away -E.g., Lower-back pain, headaches, arthritis -Recurrent acute vs. Intractable-benign (not threatening - headaches) vs. Progressive (increases in intensity over time – cancer, as the condition worsens the pain does too)  Pain: An unpleasant sensory and emotional experience associated with actual or potential tissue damage, or described in terms of such damage Pain Physiology  Despite enormous variability in how we perceive pain, there is an innate and hard-wired physiological basis for pain  Overview: -Free nerve endings in periphery -Send messages to spinal cord -Spinal tracts carry message to midbrain & thalamus -Conscious attention in brain Nociception  Contact with stimulus – Stimuli can be mechanical (pressure, punctures and cuts) or chemical (burns)  Reception – A nerve ending senses the stimulus  Transmission – A nerve sends the signal to the central nervous system. The rely of information usually involves several neurons within the central nervous system  Pain center reception – The brain receives the information for further processing and action  Can be conscious or unconscious)  3 kinds of pain perceptions (nociception) -Mechanical (crushing, tearing, etc.) -Thermal (heat or cold) -Chemical (iodine in a cut, tear gas)  Differences in types of pain attributed to differences in pain receptors (nociception)  Unevenly distributed in body -None in brain  Patients undergoing brain surgery don't need anesthetics  Location: any area of the body that can sense pain either internally or externally -External: skin, cornea and mucosa -Internal: muscles, joints, bladder, gut  a) Pain in internal organs is often sensed on the surface of the body  Types Of Nociceptors  Classified based on which environmental modalities they respond to -Thermal nociceptors activated by noxious heat or cold at various temperatures -Mechanical nociceptors respond to excess pressure or mechanical deformation (incisions) -Chemical nociceptors respond to spices (capsaicin) and chemical agents (acrolein) -Polymodal nociceptors respond to more than one of these modalities  2 different types of axons:  A-delta fiber axons -Myelinated -Action potentials travel at 20 meters/sec -Sharp pain -Thermal & mechanical  C fiber axons -Unmyleinated -Action potentials travel at 2 meters/sec -Dull or aching pain  Significance of myelination: increases speed of transmission, and so, sudden intense pain is more rapidly conducted to cerebral cortex than is slower, dull, aching pain of C-fibers  Axons extend into peripheral nervous system (PNS)  Cell bodies located in dorsal root ganglia of spinal cord Pain Pathway  Peripheral nerves (first order neurons) enter spinal cord at dorsal horn  Dorsal horn divides into distinct layers (laminae) -A-delta fibers connect to lamina I and V -C fibers connect with lamina II  In spinal cord, first order neurons project to second order neurons and cross midline to ascent spine  Left part of the brain picks up sensory information (pain) from right side of the body and vise versa  3 pain tracts: -Spinothalamic -Spinoreticular -Spinomesencephalic  Sensory aspects of pain -A delta fibers – project onto thalamus & sensory areas of cerebral cortex  Motivational/affective aspects -C fibers – thalamic, hypothalamic, cerebral cortex areas The Brain Can Influence Pain Perception  The pain from the cut of your hand eventually subsides or reduces to a lower intensity  If you consciously distract yourself, you don't think about the pain and it bothers you less  People given placebos for pain control often report that the pain ceases or diminishes Descending Pain Pathway  Ascending pain pathway to brain initiates conscious realization of pain  Descending pathway from brain modulates pain sensory -Sensations modulated at dorsal horn Despite a clear physiological role for pain, we know psychosocial factors also produce pain Up to 85% of back pain complaints don't have a clear physical basis (White & Gordon, 1982) Variables Contributing To Pain Perception  Stress -Sternbach (1986): headaches in low
More Less

Related notes for PSY333H1

Log In


Don't have an account?

Join OneClass

Access over 10 million pages of study
documents for 1.3 million courses.

Sign up

Join to view


By registering, I agree to the Terms and Privacy Policies
Already have an account?
Just a few more details

So we can recommend you notes for your school.

Reset Password

Please enter below the email address you registered with and we will send you a link to reset your password.

Add your courses

Get notes from the top students in your class.