fever

• how do above normal temps defened against microbial invasion?

  Stimulate motion, activity and multiplication of WBC and increase antibody production

  Directly kill/inhibit some bacteria/virus growth (tolerate narrow range)
• what is fever

  Defensive reaction when pathogen invades body and injures tissue, 1 response is to produce pyrogens.
• what do pyrogens do to heat-sensing & cold-sensing neurons?

  Heat: inhibit

  Cold: Excite
• Why do pyrogens inhibit/excite heat/cold- sensing neurons?

  Deceive hypothalamus -> Thinks body cooler than it is -> Raise body temp above normal range
• Fever (steps)

  1. immune cells activated (infection by-product) and secretes pyrogens
  2. pyrogens -> hypothalamus (travel by blood)
  3. Increase thermoregulatory set point, but core body temp is lower than TSP (shiver, feel cold, seek warmth)
  4. Body adjusts to increase core temp (vasoconstriction, metabolic heat rises)
  5. Now core temp = TSP, when infections cleared immune cells stop pyrogen production -> TSP revert to normal
  6. Core temp higher than TSP
  7. body adjusts (sweat, feel hot) until core temp = normal TSP
• Fever (steps)?

  1. immune cells activated (infection by-product) and secretes pyrogens
  2. pyrogens -> hypothalamus (travel by blood)
  3. Increase thermoregulatory set point, but core body temp is lower the TSP (shiver, feel cold, seek warmth)
  4. Body adjusts to increase core temp (blood vessels constrict, metabolic heat rises)
  5. Now core temp = TSP, when infections cleared immune cells stop pyrogen production -> TSP revert to normal
  6. Core temp higher than TSP
  7. body adjusts (sweat, feel hot) until core temp = normal TSP
• explain how bacterial pathogens stimulates hypo to rest thermostat and thus result in a fever:

  Macrophages respond to pathogen entry & ingests pathogen

  • Macrophages produce interleukin 1/chemicals
  • pathogen releases pyrogen
  • cytokines produce pyrogen
  • pyrogens released into blood
  • pyrogens later body temp sensors

  hypo responds to pyrogens
• Increase body temp assist in fighting pathogen:

  • Increase production of killer T cells which speed up CMI
  • increase metabolic rate = speed up tissue repair
  • increase blood flow (heart rate) -> allow lymphocytes to reach infection site faster
  • increase interferon effects -> interferes viral replication
  • creates non-optimum temp = inhibit pathogen