Temperature homeostasis Flashcards
What does it mean that humans are homeothermic?
They are warm-blooded.
Why does the body temperature need to be maintained within narrow limits?
It is essential for the maintenance of normal bodily processes.
What is the normal human average body temperature?
36.7+/- 0.5 degrees celsius.
What can alter the measured human body temperature?
Sampling site, age, gender and time of day e.g. oral, rectal or tympanic.
Why does the body temperature increase during the second half of the menstrual cycle?
The effects of progesterone.
What are sources of heat input?
Internal production and external input such as metabolism and muscle contraction and from the environment via radiation or conduction.
What are some sources of heat losses to the environment?
Radiation, conduction, convection and evaporation.
What accounts for heat losses in the body?
20-30% is from sweating and respiration and 70% is from radiation.
What is the thermoneutral zone?
The range of ambient temperature over which the heat from the basal metabolism is sufficient to maintain the body core.
What is the ambient temperature?
The environmental temperature.
What is the main physiological thermoregulatory challenge?
Low temperature.
What temperature can naked humans thermoregulate at?
Between 10-55 degrees celsius.
Where is the thermoregulatory centre?
In the hypothalamus.
What does the hypothalamus do?
It integrates sensory input from thermoreceptors located in the core and periphery (skin).
Where is an increase blood temperature detected?
The anterior hypothalamus.
Where is a decrease in blood temperature detected?
The posterior hypothalamus.
What might happen if the temperature is above 37 degrees?
Sweating, cutaneous vasodilation.
What might happen if the temperature is below 37 degrees?
Cutaneous vasoconstriction and horripilation, non-shivering thermogenesis in infants and shivering in adults.
What detects a change in environmental temperature?
Peripheral thermoreceptors.
What detects a change in core body temperature?
Central thermoreceptors.
How does vasodilation cause heat loss?
Blood flows closer to the skin so heat can be lost.
How does vasoconstriction cause heat gain?
There is decreased blood flow towards the surface of the skin so there is decreased heat loss.
What does the effectiveness of sweating as a way to lose heat dependent on?
Low environmental humidity and free access to water and sodium.
What is shivering?
Voluntary and involuntary muscular thermogenesis.
What is non-shivering thermogenesis?
A hormone induced uncoupling of mitochondrial oxidation from phosphorylation in brown adipose tissue. It is only significant in infants.
What is hypothermia?
A reduced body temperature outside of the normal range.
What is hyperthermia?
An increased body temperature above the normal range.
What is a fever?
The result of a chemical resetting of the thermal set point - temperature above 38 degrees. The body temperature stabilises at a new elevated set point.
What is the effect of endogenous pyrogens being released into the body?
They cause an increase in the thermoregulatory set point in the hypothalamus.
