Regulation of Body Temperature Flashcards
What does homeothermic mean?
Homeothermic: capable of mantaining body temperature within very narrow limits. (37C)
How do you calculate core temperature?
Rectal Temperature
What are the exogenous factors that affect body temperature?
Name 5
- Climatological environment
- Peripheral Insulation
- Diet
- Physical Activity
- Drugs
What are the endogenous factors that affect body temperature?
Name 6
- Rhythms- Circadian
- Gender (menstrual Cycle and Pregnancy)
- Age and Body Size
- Subcutaneous insulation
- Water Content
- Psychological State
What are the channels of heat transfer?
Conduction (C)
Convection (K)
Radiation (R)
Evaporation (E)
What is the formula for total energy expenditure ?
Total Energy Expendature = Internal energy produced + External work performed + Energy Stored
What is radiation?
heat transferred via emitted electromagnetic waves.
What is conduction?
Heat transfer by conduction occurs within a solid or between two or more solids in close contact.
What is convection ?
Heat transfer between a fluid or gas and a solid. Heat will be transferred and displaced.
What is evaporation?
Heat transfer occurs by means of a change in state from a liquid to a gas.
Can you ever gain heat through evaporation ?
Never. Evaporation is always heat loss.
What does the ratio of surface area to volume do to heat loss?
Higher (SA / V) = Higher Heat Loss
What does the lower temperature of the extremities in a windless environment represent?
The large SA/V ratio relative to the trunk.
What is the main component of the brain that regulates body temperature ?
Hypothalamus
What is thermoregulatory non-shivering thermogenesis?
Sympathetic nervous system stimulation. Liberation of Epi which increases metabolic rate of many tissues. SNS activation will also result in vasoconstriction.
Are thyroid hormones thermogenic?
Yes They act on Na-K ATPase increasing O2 consumption and increasing metabolic rate
What does hyopthyroidism do to body metabolism?
Thyroiditis, surgical removal of the thyroid or iodine deficiency will decrease metabolic rate and decrease heat production.
When working under conditions of high temperature you should increase your intake of what?
NaCl
What are the three things stimulated by cold that will decrease heat loss?
- Vasoconstriction
- Reduction of surface area
- Behavioral responses (warmer cloths and changing the thermostat)
What are the 4 things stimulated by cold that increase heat production?
- Increased Muscle Tone
- Shivering and increasing voluntary activity
- Increased secretion of epinephrine
- Increased appetite
What are the three things stimulated by head that increase heat loss?
- Vasodialation
- Sweating
- Behavioral changes ( turn on fan, put on cooler clothes)
What are the three things stimulated by heat that decrease heat production?
- Decreased muscle tone and coluntary activity
- Decreased secretion of epinephrine
- Decreased food appetite.
What are the risk factors of heat stroke ?
- . Elderly and bedridden patients
2. Use of anticholergenics
What is head exhaustion ?
The body’s response to increased temp included vasodialation and sweating. Excessive sweating decreases ECF volume, decreases blood volume, and decreases arterial pressure which leads to fainting
What is heat stroke?
Body temperature increases to a point of tissue damage. Usually the normal response to elevated temperature is impared (ie sweating) core temperature increases to dangerous limits.
What is malignant hyperthermia ?
A rare life threatening condition ( usually hereditary) wherein, there is a massice increase in metabolic rate, increase O3 consumption in response to inhalation anesthetics (Haloethane)
What are some exogenous pyrogens that induce fever? (Microbial)
Viruses Bacteria Mycobacteria and Fungi
What are some non-microbial pyrogens that induce fever?
Antigens
Inflammatory agents
Plant Lectins
Host derived Ab-Ab complexes.
What are the benefits of fever?
Increased neutrophil migration
Enhanced Phagocytosis
“ Interferon production
