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Why We Get Sick: Chapter 3

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Tend to avoid substances and people who may be a source of ... Encourage inactivity. Encourages effective immune responses and repair of damaged tissue ... – PowerPoint PPT presentation

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Title: Why We Get Sick: Chapter 3


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Why We Get Sick Chapter 3
  • Signs and Symptoms of Infectious Disease

By Derek Caplan
Book By R.M. Nesse and G.C. Williams
3
Types of Host Defenses
  • Hygiene
  • The Skin
  • Pain and Malaise
  • Expulsion-Based Defense
  • Defense Mechanisms

4
Hygiene
  • Best defense Avoidance of danger
  • Tend to avoid substances and people who may be a
    source of contagion
  • Feces and vomit
  • Tendency to defecate away from others
  • Social pressures may protect us from infection by
    others

5
The Skin
  • like a wall around an ancient city
  • Provides superior protection
  • Parasites
  • Mechanical, thermal, and chemical forces
  • Pathogens cannot penetrate the skin
  • Adjustable armor
  • Hygiene helps maintains the skins barrier

6
Pain and Malaise
  • An adaptation that works with the skin to cause
    avoidance and escape
  • Continued pain is adaptive, use of damaged tissue
    compromises effectiveness of adaptations
  • tissue reconstruction, antibody response to
    bacteria
  • Aches and pains are adaptive
  • Encourage inactivity
  • Encourages effective immune responses and repair
    of damaged tissue

7
Expulsion-Based Defense
  • All bodily openings provide possible entrance for
    pathogens
  • Sneezing- a defensive adaptation
  • Coughing
  • Nausea and Vomiting
  • Diarrhea
  • Urinary Tract and Reproductive System

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Defense Mechanisms
  • Macrophages
  • Helper T Cells
  • Major Histocompatibility Complex (MHC)
  • ID card
  • Immune system
  • inflammation and specialized antibodies

9
Host Adaptation
  • FeverBeneficiary?
  • Decreasing a fever when sick may cause one to
    heal more slowly
  • Withhold iron when sick?
  • Taking iron supplements when sick may cause death
  • High iron foods seem disgusting to us when sick

10
Pathogen Strategies
  • Evasion of Defenses
  • Attack on Defenses
  • Vector Transmission
  • Host Manipulation

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Evasion of Defenses
  • Door-to-Door Salesman Tactic
  • Rabies, neurotransmitter Epstein-Barr, C4
    receptor
  • Evasion of Immune System
  • African sleeping sickness, trypanosome changes
    disguises
  • Malarial Parasites, bind to walls of blood
    vessels
  • Spy Tactic
  • Some bacteria and worms have very similar
    external chemistry to human cells, difficult to
    differentiate

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Attack on Defenses
  • Pathogens seek not only to evade, but to use
    their own weaponry to gain the upper-hand
  • Staphylococcus aureus, blocks useful inflammation
  • Streptococcal infection secretes streptolysin-O,
    kills white blood cells
  • Some bacteria cause shock caused by the formation
    of of lipopolysaccharide (LPS)

13
Vector Transmission and Host Manipulation
  • Diseases may be spread through vector
    transmission by insects, carrying transport
    agents.
  • Malaria is a well known pathogen, spread by
    Mosquitoes.
  • Parasites have adapted to use the host as they
    want, called host manipulation
  • Rabies Virus

14
Conclusion
  • Host organisms have developed a number of
    defenses against pathogens
  • Pathogens have developed a number of strategies
    against the defenses of the host
  • weapons of both parties are growing, leading to
    an arms race without end (Chapter 4)

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