Physiology 3 (pt 3)

  1. Ventilation
    • Exchange of air between the atmosphere and the alveoli
    • Actual movement of respiratory gases at the terminal branches occurs due to diffusion
  2. Homeothermic
    • Maintaining body temperatures within very narrow limits despite wide fluctuations in ambient temperature
    • Allows chemical rxn in the body to take place regularly instead of fluctuating with a changing of internal temperature
  3. Shell body temperatures
    • Heat loss surface-- skin
    • Varies considerably
  4. Oral temperature at rest
    • 98.6 degrees
    • Shell
  5. Rectal temperature
    • Usually 0.7 degrees higher than oral 
    • Core
  6. Axillary temperature
    98.6 degrees but does not fluctuate with food, fluid intake
  7. Otic (ear) temperature resting
    • Shell 
    • 98.6 degrees
  8. Body temperature
    • Usually maintained between 96 degrees and 100 degrees despite changes in external air
    • Fluctuates about 1-1.8 degrees F in 24 hours (low in morning, high in late afternoon or evening)
    • Reflects the balance between heat production and heat loss and heat retention
  9. Why do women have higher temperatures during the second half of the menstrual cycle?
    • Effects of progesterone 
    • Spike on day 14, which is the basis of ovulation predictor kits
  10. What happens at 106 degrees F? 110?
    • 106: convulsions; protein denaturation
    • 110: absolute limits for life
  11. Skeletal muscle heat production during exercise
    30-40 times that of the rest of the body
  12. Radiation
    • Loss of heat in the form of electromagnetic or infrared waves (thermal energy)
    • Any dense object that is warmer than the objects in its environment will transfer heat to those objects
    • 60% of heat is lost through radiation
    • Also gain heat by absorbing electromagnetic waves from the sun
  13. Conduction
    • Transfer of heat between objects that are ihn direct contact with each other including the air or water
    • Water is a better conductor of heat so more heat is lost to water than to air
    • 15% of heat loss
  14. Convection
    • Body shell transfers heat to surrounding air
    • Process whereby conductive heat loss or gain is aided by movement of the air or water next to the body
    • Warm air expands and rises while cool air falls
    • Wind/fan is forced convection
  15. Evaporation
    • Water evaporates bc its molecules absorb heat from the environment and becomes energetic enough, vibrate fast enough, to escape as gas (vapor)
    • Removes large amounts of heat from the body surface
  16. Insensible perspiration
    • Evaporation through the lungs, mucosa of the mouth, and through skin
    • You can't feel it but you are sweating heat all the time 
    • 25% of heat loss
  17. Sensible perspiration
    • Increase temperature, exercise/stress
    • Sweat you can feel
  18. Why do people suffer heat exhaustion more frequently in humidity
    • When it is wet outside, then you loose less of your own hot, wet water
    • Dry heat allows you to sweat and you can be cooler
  19. Homeostasis of temperature
    • 37 degrees C or 98.6 degrees F
    • If heat producing mechanisms generate more heat than is lost, body temp rises
  20. Fever
    • Too high body temp destroys proteins
    • Controlled hyperthermia
    • Results from infection somewhere in the body
    • WBC release pyrogens which act directly on hypothalamus to reset thermostat to higher temperature
  21. Hypothermia
    Too low body temp causes cardiac arrhythmias
  22. Hypothalamus
    • The body's thermostat
    • Controls heat production, heat loss and heat retention
    • Receives input from peripheral thermoreceptors located in shell and central thermoreceptors 
    • Fever
  23. Two types of thermoreceptors
    • Peripheral thermoreceptors (skin)
    • Central thermoreceptors (deep body structures including the abdominal organs and hypothalamic neurons)-- Much more essential as core temperature must be kept constant
  24. Mechanisms of heat production
    • Increase of metabolic rate (NE)
    • Shivering (muscle contraction)
    • Enhanced thyroxine release
  25. Increased metabolic rate for heat
    • Norepinephrine release is stimulated by sympathetic fibers
    • Increases metabolic rate which enhances heat production
  26. Shivering in heat production
    Stretch receptors in antagonistic muscles are stimulated causing involuntary shuddering of skeletal muscles and therefore increase temperature
  27. Enhanced thyroxine release
    • When environmental temperature decreases gradually (summer to winter), the hypothalamus releases thyrotropin releasing hormone, TRH
    • Activates TSH and then more thyroxine which increases metabolic rate and increase body heat
  28. Vasodilation
    • Heat loss mechanism 
    • This of cutaneous blood vessels by inhibition of sympathetic fibers causing vessels serving the skin to dilate
    • Skin swells with warm blood
    • You turn red
    • Heat is lost by radiation, conduction and convection
  29. Sweating
    • Sweat glands strongly activated by sympathetic fibers
    • Heat is lost by evaporation 
    • Less so in humid air
  30. Decrease in insulation
    Burning of fat stores causes a decrease in insulating subcutaneous layer, therefore heat loss increases
  31. Vasoconstriction of cutaneous blood vessels
    • Blood vessels to the skin constrict keeping the blood closer to the core (heat stays in)
    • Prolonged constriction leads to tissue damage (frostbite)
  32. Raynaud's syndrome
    • Issue with blood vessels
    • Prone to migraines
    • No blood flow to fingers but there's flow to hands
  33. Other factors for heat retention
    • Decrease sweat production
    • Increased insulation (build fat)
  34. Piloerrection
    • Arrector pili muscle contraction forces hair to stand straight up while dimpling skin
    • Insulator mechanism for animals bc traps warm air in the layer of hair
  35. Mechanism of fever
    • Phagocytes enter, they secrete chemical pyrogens that circulate to the hypothalamus which releases prostaglandins 
    • This increases the hypothalamic thermostat

    Aspirin, ibuprofen, Tylenol all inhibit prostaglandins so reduce fever
  36. Chill stage of fever
    • Increased pyrogens in blood raises the thermostat setting
    • Causes the hypothalamus to respond to too low of body temp by stimulating heat production
    • Even though body core's temp is rising, the skin remains cold and shivering occurs
  37. Fever breaks
    • Decreased pyrogens in blood lowers the thermostat setting back to normal
    • Causes hypothalamus to respond to too high of body temp
    • Skin becomes warm and person sweats
  38. Crisis stage of fever
    • Danger of fever that is if the thermostat is set too high
    • Proteins may denature and permanent brain damage may occur
  39. Danger ranges body temp
    Above 110 and below 75
  40. Hypothermia
    • Decrease in body temp, reduces metabolic rate, can be deliberate (surgery) or accidental 
    • Subdivided into 4 different degrees: mild
    • (90–95 °F); moderate, (82–90 °F); severe, (68–82 °F) and
    • profound (at less than 68 °F)
  41. Difference between mild/moderate and severe/profound hypothermia
    • Mild/Moderate Hypothermia: discomfort, shivering, apathy
    • Severe/Profound Hypothermia: depressed body temp, absence of shivering, unconsciousness

  42. Heat exhaustion
    • Body is trying to cool you
    • Sweating, heat loss mechanisms caused by dehydration
    • Temp may be elevated but not above 104
  43. Two types of heat exhaustion
    • Water depletion: signs include excessive thirst, weakness, headache, and loss of consciousness
    • Salt depletion: signs include nausea, vomiting, muscle cramps and dizziness

  44. Heat stroke
    • Homeostasis fails, the body cannot control heat/temp anymore, rapid rise in temperature, rises to the point at which brain damage or damage to other internal organs may result
    • Temperature may reach 105oF or greater
    • Red, hot, dry skin

  45. Biggest differences between heat stroke and exhaustion
    • Exhaustion: sweaty skin
    • Massage cramping muscles
    • Spray cool water
    • Take cool shower
    • Remove clothing

    • Stroke: red, hot, dry
    • Elevate pts feet higher than their head to reduce shock
    • Remove clothing and cool with water
    • Use ice packs and cool drinks
Card Set
Physiology 3 (pt 3)