Histo Lecture 15

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Author:
paffman7
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74231
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Histo Lecture 15
Updated:
2011-03-21 16:10:02
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PT624
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Body Temperature Regulation
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  1. What are the 2 main ways systemic temperature is controlled?
    • Heat production
    • Heat dissipation
  2. What structure coordinates the body's response to change in core temperature?
    Hypothalamus
  3. What are some ways that the body produces heat?
    • Basal rate of ellular metabolism
    • Metabolism due to muscle acitivity
    • Increased metabolism due to thyroxine (thyroid hormone)
    • Norepi, epi, and sympathetic stimulation of cells
    • Increased cell metabolism with temperature increases
    • Cellular metabolism for digestion, absorption, and storage of food
  4. Most body heat is produced in what deep organs?
    Liver, brain, heart, skeletal muscles
  5. What does the body have as insulators?
    • Skin
    • Subcutaneous tissue
    • Subcutaneous fat
  6. What is a part of hte heat radiator system?
    Skin blood flow
  7. Degree of vasoconstriction of the skin vasculature determines what?
    Heat conduction by the skin
  8. Sympathetic system acts in response to:
    • Body core temperature
    • Changes in environmental temperature
  9. What is radiation?
    Transfer of heat in the form of infrared rays
  10. Radiation accounts for how much heat loss from the body?
    60%
  11. What is conduction?
    Kinetic energy of molecular motion is transferred (as heat) from the skin to the environment
  12. When does conduction NOT occur?
    What are and skin temperature are the same
  13. What is convection?
    Heat loss from the body due to air currents
  14. What two heat loss systems are increased when submerged in water?
    • Convection
    • Conduction
  15. Sweating is controlled by what?
    ANS (sympathetic) in response to body temperature
  16. What is responsible for signaling the sympathetics to increase sweating?
    Anterior hypothalamus
  17. Sympathetic system innervation to sweat glands utilizes what neurotransmitter?
    Acteylcholine
  18. What stimulates glandular cell secretion?
    Cholinergic fibers
  19. Composition of initial sweat is similar to what?
    Plasma
  20. Where are some temperature receptors?
    • Receptors in skin to monitor surface temperature
    • Deep body temp receptors (spinal coard, abdominal viscera, great veins)
  21. Deep receptors send their information where?
    Posterior hypothalamus
  22. Increased body temp stimulates:
    • Vasodilation of skin vessels (inhibit sympathetics)
    • Increased sweating (stimulate sympathetics)
    • Inhibition of excess heat production (chemical thermogenesis)
  23. Decreased body temp stimulates:
    • Vasoconstriction of cutaneous vessels
    • Piloeretion
  24. What are some ways we can increase thermogenesis?
    • Shivering
    • Sympathetic stimulation of chemical thermogenesis
    • Thyroxine secretion
  25. What is shivering?
    Increase in muscle tone beyond normal threshold stimulates shivering
  26. How much can shivering increase body heat production?
    4-5X
  27. What neurotransmitters are capable of "uncoupling" oxidative phosphorylation?
    Norepi and epi
  28. What is the cascade for creating tyroxine?
    Hypothalamus-> TRH -> TSH -> T4 (thyroxine)

    • TRH - thyrotropin releasing hormone
    • TSH - thyroid stimulating hormone
  29. What is the "set point"?
    98.6 degrees F
  30. What is fever?
    Body temperature above normal range
  31. What stimulates the hypothalamus to increase core body temperature?
    Prostaglandins
  32. What OTC medicines do we use to inhibit prostaglandin formation?
    Aspirin & Tylenol
  33. What are the 3 phases of fever?
    • Phase 1 - increase in core temperature
    • Phase 2 - Maintenance of increased temperature
    • Phase 3 - Resolution of fever; Return to normal core temperature; Crisis/Flush
  34. During phase 1 in fever, why do we feel chills?
    The hypothalamus has increased the set point and the actually body temp is below it, so shivering increases the body temp to reach the new higher set point.
  35. In phase 3, why do we sweat?
    When the fever breaks, the hypothalamus lowers the set point. At that point the body temp is still high from the fever, so we sweat to derease to try and reduce the temperature to return to the now-set-to-normal set point
  36. What causes spasms in muscles?
    • Fluid level and electrolyte imbalance
    • NaCl lost via sweat
  37. What are some symptoms of heat exhaustion?
    Weak, rapid pulse, low BP, headache, dizziness, general weakness
  38. What causes heat exhaustion?
    Excessive sweating causes ineffective circulatory adjustments (reduced perfusion to body)
  39. At what temperature is it considered heat stroke?
    104 degrees F
  40. What are the symptoms of heat stroke?
    Dry, hot skin, headache, fatigue, confusion, vomiting, unconsciousness

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