The document discusses the mechanisms of fever and thermoregulation in the hypothalamus. It explains that fever occurs in three stages: 1) increased heat production causes a rise in body temperature and chills, 2) temperature stabilizes as heat production and transfer balance at a higher level, and 3) heat production decreases below transfer levels, reducing temperature through sweating. The hypothalamus contains heat production and transfer centers that are impacted by exogenous and endogenous pyrogens to shift the thermoregulatory set point and trigger the mechanisms of each fever stage.

1. Fever

2. Functional organization of the
thermoregulatory center of the
hypothalamus
setting point
Cold
neurons
Thermal
neurons
Heat Production Center
Heat transfer center
Central thermoreceptors

3. Exogenous Pyrogens
Endogenous pyrogens (IL-1, IL-6,
γ - interferon, TNF)
Center Neurons
hypothalamic thermoregulation: the formation of prostaglandinE2
Increased sensitivity of cold receptors hypothalamus
Hypothalamic «setting point» offset
Activation mechanisms
heat products
Reduced efficiency
heat transfer mechanisms
Fever
The reasons
fever

4. Mechanisms for changing heat transfer and heat
production in various stages of fever
I stage. Increase in body heat
(HT>HP)
heat production heat transfer
the formation of heat by the body heat transfer
due to evaporation, radiation
convection
contractile non-contractile by
thermogenesis thermogenesis
(дрожь) (oxidative peripheral vasoconstriction
processes)
reduce skin blood flow,
decreas sweating
The emergence and intensification of a feeling of cold
(chills)

5. Mechanisms for changing heat transfer and heat
production in various stages of fever
2nd stage - standing temperature
(HP=HT)
Thermoregulation balance is set at a higher level than normal
HP HT
the formation of heat by the body heat transfer by the body by
radiation, convection
due to by
non-contractile expansion of the peripheral
thermogenesis vessels of the skin, thermal
(oxidative processes) dyspnea (respiratory
function activation)
The emergence and intensification of a feeling of heat

6. Mechanisms for changing heat transfer and heat
production in various stages of fever
3rd stage - temperature reduction
(HP<HT)
HP HT
Normalization of heat production heat transfer
by the body evaporation, radiation,
convection
due to by
non-contractile peripheral sweating
thermogenesis vasodilation diuresis
(oxidative processes)
cutaneous
blood flow
Decreased feeling of heat, sweating