Feedback Control: Temperature and Vital Signs Flashcards
what are all the vital signs?
pulse (60-100)
blood pressure (120/80)
resp. rate (12-20)
oxygen saturation (96%+)
temperature (37degrees)
consciousness (AVPU)
capillary refill time (<2 seconds)
what is meant by core body temperature
the temp. of blood and internal organs (37.8 degrees Celsius)
what is meant by normothermia
the optimum for cellular function and metabolism
*very important to maintain body temperature in a narrow range ie overheating would lead to proteins denaturing and decreased wouldn’t be enough for metabolic activities and cellular functions to be carried out
what is normal tympanic temperature
36 - 37.5 degrees
what is the temperature of a fever
38 - 40 degrees
Abnormal
what is the temperature of hyperthermia
40 + degrees
Abnormal
when would hyperthermia be considered
<35 degrees Celsius
what sites should be avoided when finding out core body temperature
peripheral sites ie sublingual/oral/axilla
where would you examine to find out a direct estimate of core body temperature?
rectal or oesophageal
when does body temperate vary
> in each individual - ie everyones normals are different
usually lower in the morning and higher in the evening - diurnal variation
may be altered by exercise, activity, emotions or exposures to certain temperatures
varies during the menstrual cycle - ie higher in the 2nd half of the cycle (from the time of ovulation)
how does our body gain heat
internally from metabolic heat game
externally from radiation
how do our bodies lose heat
externally from radiation conduction convection and evaporation
what is the BMR
basal metabolic rate : it is the minimum amount of energy required to sustain vital body functions
- it also leads to a basic level of heat production
- the BMR can be increased by hormones such as adrenaline, noradrenaline and thyroxine
other than the BMR what’s another way of gaining heat
muscle activity/shivering
where are the central thermoreceptors in the negative feedback control mechanism for temperature?
in the hypothalamus, abdominal organs
where are the peripheral thermoreceptors
in the skin
what are the effectors in this negative feedback system
- skeletal muscles
- skin arterioles
- sweat glands
where is the temperature control centre
hypothalamus
what are the two centres of the hypothalamus, and what stimuli activates each one?
there is the posterior and anterior hypothalamic centre
posterior is activated by the cold
anterior is activated by the warm
what are the neural connections associated with the hypothalamus
- limbic system
- cerebral cortex
- motor neurons
- sympathetic nervous system
what is the posterior hypothalamic centre response when activated by cold?
vasoconstriction (skin arterioles)
increased muscle tone and shivering (skeletal muscles)
postural changes and warm clothing (behavioural adaptations)
what is the anterior hypothalamic centre response
vasodilation
sweating
decreased muscle tone, decreased
voluntary movement
cool clothing
how does the set point of body temperature change in fever?
-if we have infection of inflammation this leads to the release of endogenous pyrogens ie interleukins (from macrophages)
-these pyrogens then stimulate the release of prostaglandins in the hypothalamus and this then resets the temperature set point in the hypothalamus to be higher
-this then activates the ‘cold response’ (the set point is now higher but core body temperature will be the same)
this then results in increased heat production and decreased heat loss
(which raises body temp)
= fever
how would the hypothalamic temperature set point be restored to normal?
if the body manages to fight the cause of pyrogen release ie the cessation of pyrogen release / antipyretics
or
if prostaglandin synthesis is decreased / ceased
how does the hypothalamus restore the set point back to normal ?
the hypothalamus initiates mechanisms to cool the body ie ‘hot response’ to reduce the body temperature to the normal set point
ie feeling sweaty and hot after feeling shivery and cold is a good thing
