Physiology 3 (pt 3)

• Exchange of air between the atmosphere and the alveoli
• Actual movement of respiratory gases at the terminal branches occurs due to diffusion

• 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

• Heat loss surface-- skin
• Varies considerably

• 98.6 degrees
• Shell

• Usually 0.7 degrees higher than oral 
• Core

98.6 degrees but does not fluctuate with food, fluid intake

• Shell 
• 98.6 degrees

• 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

• Effects of progesterone 
• Spike on day 14, which is the basis of ovulation predictor kits

• 106: convulsions; protein denaturation
• 110: absolute limits for life

30-40 times that of the rest of the body

• 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

• 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

• 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

• 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

• 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

• Increase temperature, exercise/stress
• Sweat you can feel

• 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

• 37 degrees C or 98.6 degrees F
• If heat producing mechanisms generate more heat than is lost, body temp rises

• 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

Too low body temp causes cardiac arrhythmias

• The body's thermostat
• Controls heat production, heat loss and heat retention
• Receives input from peripheral thermoreceptors located in shell and central thermoreceptors 
• Fever

• 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

• Increase of metabolic rate (NE)
• Shivering (muscle contraction)
• Enhanced thyroxine release

• Norepinephrine release is stimulated by sympathetic fibers
• Increases metabolic rate which enhances heat production

Stretch receptors in antagonistic muscles are stimulated causing involuntary shuddering of skeletal muscles and therefore increase temperature

• 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

• 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

• Sweat glands strongly activated by sympathetic fibers
• Heat is lost by evaporation 
• Less so in humid air

Burning of fat stores causes a decrease in insulating subcutaneous layer, therefore heat loss increases

• Blood vessels to the skin constrict keeping the blood closer to the core (heat stays in)
• Prolonged constriction leads to tissue damage (frostbite)

• Issue with blood vessels
• Prone to migraines
• No blood flow to fingers but there's flow to hands

• Decrease sweat production
• Increased insulation (build fat)

• 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

• 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

• 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

• 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

• Danger of fever that is if the thermostat is set too high
• Proteins may denature and permanent brain damage may occur

Above 110 and below 75

• 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)

• Mild/Moderate Hypothermia: discomfort, shivering, apathy
• Severe/Profound Hypothermia: depressed body temp, absence of shivering, unconsciousness

• Body is trying to cool you
• Sweating, heat loss mechanisms caused by dehydration
• Temp may be elevated but not above 104

• Water depletion: signs include excessive thirst, weakness, headache, and loss of consciousness
• Salt depletion: signs include nausea, vomiting, muscle cramps and dizziness

• 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

• 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