warmer core
37oC
central thermoreceptors
hypotalamus, spinal cord
perpheral (skin)
thermoreceptors
centre of thermoregulation
hypotalamus
TSH-RH
TSH
T3, T4
ANS - sympathicus
somatomotor NS
metabolism
brown adipose
tissue
sweat glands
vazomotor
activity
muscle
shivering
muscle
activity
Mechanisms of heat production
• metabolism
• skeletal muscle tone
• muscle shivering
• chemical thermogenesis in brown adipose tissue
And helping
• vasoconstriction – heat saving
• voluntary mechanisms - behaviour
Mechanisms of heat loss
• radiation
• conduction
• convection
• evaporation
And helping
• vasodilation
20oC
30oC
36oC
radiation
61%
46%
0%
convection
26%
27%
0%
evaporation
13%
27% 100%
Fever
stages
•
•
•
•
prodromal stage
stadium incrementi - temperature raise
stadium acme – culmination of fever
stadium decrementi – decrease of temperature
Fever – prodromal stage
exogenous pyrogens
lipopolysaccharides
endogenous pyrogens
IL-1, IL-6, TNF
hypotalamic thermostat
arachidonic acid
cyclooxygenase
PGE2
increased set point
ASA
ibuprofen
Stadium incrementi
• increase of heat production and saving of
heat
•
•
•
•
vasoconstriction – white, cold skin
higher muscle tone
muscle shivering
behaviour – warm dress, warm covers
Stadium acme
• body temperature is maintained at the new level until
the fever breaks.
• endogenous antipyretics
– arginine vasopressin
– melanocyte-stimulating hormone
– ACTH-RH
• exogenous antipyretics
– acetylsalicylic acid
return the set point
to normal
Stadium decrementi
• decrease of heat production and heat loss
• vasodilation
• sweating
Difference between fever and hypertermia
39
Hypertermia
real temperature
38
37
set point
thermoregulation failure
Difference between fever and hypertermia
39
Fever
real temperature
38
37
set point
thermoregulation failure
NO! normal thermoregulation
Classification of fever
Intensity
• subfebrility + 0,5oC
• middle fever + 2oC
• high fever
+ 3oC
• very high fever + > 3oC
Classification of fever
febris continua (pneumonia)
febris remittens (infective endocarditis)
febris intermittens alternation of febrile and
nonfebrile periods (sepsis)
undulant fever (brucellosis)
febris recurrens return of fever (malaria)
febris atypica fever in the morning (typhus abdominalis)
Classification of fever
Length
• febris ephemera
• febris acuta
• febris chronica
1 day
Benefits of fever
• kills thermolabile microorganisms
• it has adverse effects on growth and replication of
some microorganisms
• decrease of serum level concentration of iron, zinc,
copper which are needed for some microorganism
• lysosomal breakdown
• effect on phagocytosis
• production of antiviral interferon