7: Feedback control of body temperature Flashcards
Temperature is an example of a variable which must be maintained within narrow limits in the human body. This process is called _______.
Homeostasis
What is the definition of core body temperature?
The temperature of structures deep within the body
What is the average core temperature of a human (to 3 significant figures)?
37.8 degrees Celsius
Why isn’t the skin a good site for monitoring body temperature?
The temperature of the skin varies widely
The core body temperature is kept ____ despite changes in the environment.
constant
What is nomrothermia?
The normal core body temperature
What is ear drum temperature also known as?
Tympanic temperature
Name three areas where body temperature can be taken.
Ear drum, rectum, orally
What is diurnal variation in body temperature?
Changes in body temperature during the day
To maintain a constant core body temperature, heat ___ and heat ___ must be in balance.
gain , loss
What is a source of heat gain within the body?
Metabolic heat
What is Basal Metabolic Rate (BMR)?
Minimum amount of energy required to sustain vital body functions
Which hormones increase the Basal Metabolic Rate (BMR)?
Adrenaline, noradrenaline, thyroxine
Shivering increases ___ production by increasing ___ ___.
heat , muscle activity
What is radiation?
Emission of heat energy from a surface as electromagnetic waves
The human body both ___ and ___ radiant heat.
emits , absorbs
How much of the body’s heat loss occurs through radiation?
Around 50%
What is conduction?
Transfer of heat between objects in contact
In conduction, heat moves from the ___ to ___ object.
warmer , cooler
What is convection?
Transfer of heat energy away from the body by air or water currents
Warm air ___, cool air ___.
rises, falls
Convection and ____ often work together to dissipate heat from the body.
conduction
What is evaporation?
Conversion of water into vapour using energy
Where does evaporation occur in the body?
The skin surface, lining of the respiratory tract
Sweating is an ___ form of evaporative heat loss.
active
Sweating is controlled by the _____ nervous system.
sympathetic
What kind of feedback control system regulates core body temperature?
Negative feedback
What is the temperature control centre called?
The hypothalamus
The posterior hypothalamic centre is activated by ___.
cold
The anterior hypothalamic centre is activated by ___.
warmth
What do skin arterioles do in response to cold?
Vasoconstrict
What does vasoconstriction result in?
Decreased heat loss / heat conservation
What do skeletal muscles do in response to cold?
Increase their muscle tone Shiver
What do skin arterioles do in response to warmth?
Vasodilate
How does vasodilation increase heat loss?
Increases blood flow to the skin, increased radiation/convection/conduction
Macrophages release chemicals in response to infection or inflammation. What do these chemicals act as?
Endogenous pyrogens
Endogenous pyrogens stimulate the release of which chemical in the hypothalamus?
Prostaglandins
What do prostaglandins to the body’s internal thermostat?
Reset it at a higher temperature
Is the resetting of the body’s internal thermostat reversible? How?
Yes When pyrogen / prostaglandin release stops
Fever is a core body temperature between…
38 - 40 degrees Celsius
What is hyperthermia (definition, not values)?
Extreme uncontrolled increase in body temperature
What body temperature constitutes hyperthermia?
Any body temperature above 40 degrees Celsius
What is hypothermia (definition, not values)?
Drop in body temperature below that required for metabolism and function
What body temperature constitutes hypothermia?
Any body temperature below 35 degrees Celsius
