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PSYCH 3M03 (10)
Chapter 6

Lecture Notes Week 6 - Oct 4 - Chapter 6 - PSYCH 3M03

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Aadil Merali Juma

LECTURE 6 PSYCH 3M03 Chapter 6: Pain and Fear October 4, 8, 2013 Pain and Fear Thermoregulation  Cutaneous receptors o Receptors in skin  Reflexes o Eg/ Withdrawal of hand when touch hot object; pain of heat straight to spinal cord then rapid involuntary response  Integration of autonomic, endocrine, and skeletomotor mechanisms o Eg/ panting  Hypothalamic regulation o Presumably integrates into drives and behaviour o Specific regions of hypothalamus that are more implicated than other areas o Heat dissipation response  Anterior regions (hot; dissipate) (in dogs)  Stimulate area – panting response  Lesion area – panting diminishes  Posterior regions (cold; conserve)  Stimulate area – shivering response  Lesion area – shivering response is lost  Behaviour  Mechanisms are very well understood Pain  Highly adaptive – necessary for survival o If you cannot feel pain, it will result in physical damage; eg/ if you do not withdraw your hand from heat, it will result in bad burns  Psychological dimensions that are confusing – become very focused on trivial injuries, yet pain is innate  Subjective  Amount perceived often not proportional to injury  Body language associated with pain  Clear “hard-wired” basis – innate  Adaptive Value o Disincentive for maladaptive and self-injurious behaviour  Where fear comes from o Punishes activity when rest and recovery are needed  Physiology o Receptors (nociceptors)  In most organs of the body (not the brain), skin, muscle – full of receptors  Free nerve endings (will leave to pain following injury)  Mechanical and thermal o Fibers  C fibers  Unmyelinated (lack of fatty acid sheath that surrounds neurons that help in rapid conduction)  Slow, dull aching pain  A∂ fibers  Thick, myelinated  Sharp, fast, pricking  Eg/ stub toe, burn hand  Quickly subsides  Synapse  Dorsal horn of spinal cords o Fibers project to the dorsal (back) horn of the spinal cord and synapse – nerve doesn’t go straight to the brain; if chemical transition occurs, then it is sent up to the brain  Messages can be blocked – message may not reach consciousness due to blockage of ascending messaged o Endorphin dynamics o Interneurons – short axons, may modulate critical synapse that sends the message to the brain o Pain tracts to the brain – 3 primary (total 5) 1 LECTURE 6 PSYCH 3M03  Spinothalamic  thalamus  Spine to thalamus – thalamus relays sensory information to other parts of the brain (?)  Spinoreticular  reticular system  Pons, medulla, oblongata, midbrain interconnecting to other areas related to reticular formation  Wakefulness, general activating systems in the brain  Spinomesencephalic  midbrain  Mesencephalon – midbrain  Sensory processes  Ascending tracts; brings information to brainstem then to other areas of the brain  Natural Analgesia o Dulled pain; pain suppression o Endorphins – from pituitary during stress  B-endorphin – comes from the anterior pituitary; released in response to CRF/CRH (hypothalamus, stimulates anterior pituitary to stimulate ACTH simultaneously); ACTH and B-endorphin come from the same split off molecule  Competitive sports, physical activity that requires intense attention – will sustain a minor injury and won’t feel it o Enkephalins – small peptides, diverse sources  All over the brain; from adrenal medulla and other places in the body  Don’t entirely understand; know chemical map around body  Cause pain suppression o Descending tracts, from brain to spinal cord, can inhibit pain messages at spinal synapses  Fewer than those that ascend o PAG – locus of opiate action, stimulation produces profound analgesia; endorphin receptors present here  Periaqueductal grey th  Largely around 4 ventricle and other parts of the central canal of the spinal cord (also carries CSF)  Critical for analgesia  Drugs that suppress pain are acting on endorphin receptors in the area of the midbrain where cell bodies that descend originate  Electrically stimulate a live animal near in PAG, can make them impervious to painful stimuli (won’t react); locally give drugs (opiate drugs; like morphine) to PAG, won’t show pain  Anticipation of pain is often far worse than the relative – anticipation leads to motivation Fear  Nature of fears stimuli o Constrained by innate processes  Eg/ crawling babies display innate fear of heights; coaxed to crawl across a table with a portion of clear glass, can see the height and will not cross the glass o Ancestral dangers (eg/ heights, predators, snakes, spiders, darkness); yet do not fear cars, traffic etc even though they are very dangerous because we have not yet adapted to it  do not fear the dangers of today, but the dangers of our ancestors environment o Less fear of novel but real dangers o Rapid one-trial conditioning occurs, very resistant to extinction  Conditioned avoidance and social transmission o Some stimuli associated with rapid, one-trial conditioning, others learned slowly if at all  Eg/ Alligators vs. rabbits; difficult to teach a monkey to fear a rabbit; teach monkey to fear alligator is rapid  Eg/ Keep monkey in captivity and isolation; first time shown a snake, shows fear response o Social transmission of fear widely observed (words can be sufficient for people and some other species)  Eg/ Baboons – when one had been shot in particular location, baboon troop no longer came to location  Eg/ Mad cow epidemic – human meat eating behaviour; AIDS – human sexual behaviour o Single traumatic event or series of sub-traumatic events can lead to very strong conditioned avoidance  Eg/ Postman condition fear of dogs slowly o Once learned, avoidance responses can be very difficult to unlearn o Tend to avoid more than we need to  Nature of response to dancer o Constrained by innate processes o Some responses cannot be easily learned o Other responses (fleeing, freezing, fighting, hiding) may occur without learning and can interfere with learning  Species-specific defense reactions o Eg/ Cannot teach rat to press a bar to rid of shock because rats are too focused on jumping out of the cage o Responses  Fleeing, hiding, freezing 2 LECTURE 6 PSYCH 3M03  Eg/ Deer in close proximity to predator; running will alert the predator, freezing it may not see deer  Fighting  Burying, burrowing  Species-specific  Eg/ Put smell of death in a rats cage, will bury
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