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Chapter 4

Ch. 4 - Causes of Pathology.docx

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PSYC 208
Paul Wehr

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Causes of Pathology 10/10/2012 10:03:00 AM Announcements  October 24 : review session from 2pm – 6pm @ Kenny 1910 Introduction  All pathology has a genetic basis, pathology decreases fitness  Why does pathology exist? Why has natural selection failed to eliminate pathology?  Medicine & Social Sciences focus on proximate explanations of disease o E.g. psychiatrists o Focuses on proximate explanations – how does… (ignores ultimate explanation) o In medicine, there is no room for evolutionary biology to be added  Teleology: error of explaining in terms of purpose or goal: what is the function of the sun? o Explaining the past from the future is an error (teleology)  Saying that the sun’s purpose is composed of sunsets, photosynthesis, light, heat, gravity suffers from teleology  The sun was created before the earth; it could not have predicted that there would be life, so it’s purpose is not any of the above o Explaining the future from the past is not an error (evolution)  Evolution of bipedalism  Causes of pathology o Infections o Defenses o Diseases of civilization o Genetic quirks o Design compromises o Evolutionary legacies Infection  Bacteria and viruses o Pathogen-host coevolution: never-ending evolutionary war  Bacteria evolves against our immune system  Viruses live inside your cells, bacteria lives outside o Pathogens attempt to subvert our defenses  Major cause of death  Antibiotics o Penicillin attacks and kills bacteria (tuberculosis & pneumonia)  Found in fungus (antibiotics are used by mushrooms to fight off bacteria) o Rates of infectious disease quickly began to decrease o Bacteria began to evolve defenses against antibiotics  Staphylococcal bacteria  In warfare, most soldiers died from this  Soldiers get injured  try to patch them up  they die anyway  1941: all strains vulnerable  1944: strains begin evolving enzymes that break down penicillin  1994 – 95% of strains at least partially resistant o Overuse in hospitals and factory farming has led to an increase in infection rates (faster evolution)  Salmonella, E. coli, and tuberculosis  The more often you use bacteria, the more you expose the bacteria, hence the faster they are able to evolve  Bigger problem is factory farming (bring thousands of animals together to make them cost effective + increase profits)  Animals are incredibly stressed because they weren’t evolved to live in such close proximity  If one of them develops an infection  infection spreads to all the animals, so to counteract this, factory farmers feed all the animals antibiotics  Antibiotics are used to prevent infections and make the animals bigger  How does this occur? o Lots of bacteria with a few resistant strains  antibiotics kill all the normal bacteria, but the resistant strains stay alive  resistant strains reproduce  new resistant strain is born Defenses  Responses to disease that are sometimes confused with disease (definitely NOT disease) o Expulsion: mucus, cough, sneezing, nausea & vomiting, diarrhea & menstruation are all functions to remove disease agents o Fever: increase in temperature kills microorganisms; survival rate for syphilis increase when infected with malaria to induce fever  Prevents microorganisms from reproducing  Syphilis by itself does not provoke fever  Fever-reducing medication prolongs sickness (less expulsion of disease) o Iron-depletion: bacteria consume iron  Body reduces iron levels in response to infection  Reduce consumption of iron-rich foods  Body reduces iron absorption  Treating/blocking a defense can be detrimental o Fever reducing medication prolongs illness o Iron supplements increase infection rates o Anti-diarrheic doubles recovery time from Shigella infection Anxiety as a Defense?  Anxiety is a non-specific increase in physiological activity and has a negative subjective experience  Anxiety is an adaptive response to stress o Fight or flight response: Hypothalamus-Autonomic-Adrenal response  Uses autonomic nervous system  Communicates with adrenal medulla (inner part of adrenal gland) o Chronic stress: Hypothalamus-Pituitary-Adrenal Response (HPA) increases  E.g. before exams, during public speaking…  Uses endocrine system  Communicates with adrenal cortex (outer part of adrenal gland)  Anxiety in guppies confronted with smallmouth bass: o Three groups: timid (hiding), ordinary (swam away, didn’t hide), and bold (vigilant, keeps eye on bass, but doesn’t swim or hide) o 6 hours later: 40% of timid, 15% of ordinary, and 0% of bold remain  Is it a good idea to treat anxiety with medication? o Hasn’t been a well thought out question o Medical research does not ask this question (if someone is anxious, they give them anti-anxiety medication) Causes of Disease  Diseases of civilization: mismatch between design and environment o Cause of much preventable disease o High-fat diet: heart disease & Type II diabetes  Because of ancestral humans  needed to eat more fat o Toxins: cancers o Competition for resources, social status, and romantic partners is more intense: chronic activation of HPA stress reaction  More intense competition in modern day o Separating mother and child following birth; infant sleeping in separate room: insecure attachment  Used to take newborn to an incubated area right after birth to ensure that the newborn isn’t exposed to infections (run tests on them first) o Substance abuse  Opiates (morphine, opium…) stimulate endorphin receptors in the brain  THC (marijuana) stimulates receptors in the brain  Alcohol increases GABA activity  Cocaine increases catecholamine activity  Modern forms of these products are more potent and more readily available  leads to diseases of civilization Genetic Quirks  Genes that only express their negative effects in the modern environment  Some cases of heart disease caused by allele that codes for abnormal metabolism of cholesterol o Inconsequential except when combined with high-fat diet o Would not have occurred in ancestral societies  Myopia: makes far objects more difficult to see o 25% of Americans have Myopia, but hunger-gatherer populations have very low incidence of Myopia. Why?  Should have been selected out in hunter-gatherer societies because it’s bad if you can’t see predators in the far distance  Myopia doesn’t appear in kids of hunter-gatherer societies, only modern societies o Incidence of Myopia increased to 25% in Native peoples when children started attending school. Reading and writing at a young age causes impaired vision later in life. Why?  Eye growth depends on feedback from the brain, which is sensitive to blurring  When you perceive something as blurry, the brain instructs the eyes to grow in that direction  Ensures coordinated development of the eye, but close work leads to an oblong shape  When you’re focused on something, your peripherals are blurred, so your brain instructs the eye to grow in that direction  oblong shape  Reason for Myopia: school  focusing on one thing for a long time  Reading, writing, staring at computers Design Compromises  Costs associated with adaptations appear as flaws o Adaptations are not optimal: sufficiently well designed to perform their function for as long as normally needed  Anxiety o Prolonged stress response uses extra calories, interferes with attention, and damages tissues and the immune system  You become scared unnecessarily  Using the fear system is costly, not free o Fight/flight response: “misses” are more costly than “false alarms”  Miss: stimulus is present, but response is absent  False alarm: stimulus is not present, but response is  Hit: stimulus is present, response is present  Correct rejection: stimulus is absent, response is absent  Natural selection allows for more false alarms, since they’re better than more misses (even though it’s costly) o Low threshold leads to many “false alarms” o Adaptive conservatism or “smoke detector principle”  “False alarms,” but the fear system rarely misses when there actually is danger o Too costly to design a system with no errors Theory of the Mind  Theories about the nature of “mind” o Ability to recognize other minds as distinct from own  I can try to anticipate what your knowledge base is o Ability to know the contents of other minds o Ability to know that thoughts and desires motivate behavior  Content of minds leads to behavior o False beliefs: a belief that does not reflect reality  Under four years cannot appreciate false beliefs (e.g. candy box full of crayons)  We are not born with theory of mind  Children rarely lie (requires theory of mind to lie)  Understand that somebody can believe something that is not necessarily true  Design Compromise o Benefits: predictability and enormous flexibility o Cost: long developmental period makes it vulnerable to disruption (pathogens, toxins, malnutrition)  The longer the developmental period, the greater the chance that it will be disrupted o Cost: potential dysfunctional development (e.g. paranoia: others can read their mind, mistake own thoughts for insertions) Evolutionary Legacies  Evolution makes small modifications to existing structures  Evolution cannot create new traits de novo  Back pain and bipedalism o o There is weight pushing down on the concave curvatures  back pain o Travel long distances using minimal energy and use hands for carrying o Complex reorganization of the pelvis and vertebral column o Double “S” curve centers weight over the feet and reduces muscle tension required to maintain balance o Vertical alignment of internal organs and higher center of mass lead to lumbar and cervical prolapses (slip discs) o Double “S” structure begins developing at 3 months, when infant begins to control the head Canadian Cancer Statistics  Estimated 186,400 diagnoses in 2012 o 28% of cancers for women is breast o 27% of cancers for men is prostate  Prognosis: 38%
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