hypothalamus, temperature regulation. the balance between heat production and heat loss, determine...
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Hypothalamus, temperature regulation
The balance between heat production and heat loss, determine body temperature
Heat production
From all vital process in the body, endocrine, muscular exercise & foods intake
Heat loss
Radiation, conduction & evaporation
Normal body temperature 36.3 - 37.1 CCore temperature undergo regular
circadian fluctuation of 0.5 - 0.7 C
Temperature regulating mechanisms
Skin, deep tissues, spinal cord, extrahypothalamic region of the brain & hypothalamus (send information about body temperature through sensory receptors (cold receptors))
Hypothalamus integrate information, then produce integrated body temperature
Temperature regulating mechanisms
Heat conserving mechanisms: Shivering Hunger Increased voluntary activity Increase secretion of A & NA Cautious vasoconstriction Curling up horripilation
Temperature regulating mechanisms
Heat loosing mechanisms Coetaneous vasoconstriction Sweating Increased respiration Anorexia Apathy & inertia
Fever
During fever the thermoregulatory mechanism behave as if they were adjusted to maintain body temperature at higher levels
Resetting of the thermostat to new temp. above 37C
temp. receptors then signals that the actual temp. is below the new set point
Temp. raising mechanisms activated
Pathogenesis of fever
Indotoxins (from bacteria), inflammation
»»»»» act on monocytes, kupffer cells & macrophages to produces cytokines (act as endogenous pyrogens)
»»»»» activation of preoptic area of hypothalamus
»»»»» prostaglandin release in hypothalamus
»»»»»raise temp. set point »»»»» Fever
Benefit of fever
Inhibit microrganisms growthAntibody production increase when temp.
elevatedSlow growth of some tumours (lymphoma)
High temp. is harmfulPermanent brain damage if rectal temp.
above 41C Above 43C heat stroke develop & death
Malignant hyperthermia (gene mutation)
Excess Ca released during muscle contraction
»»»»» contracture of muscle
»»»»» increased muscle metabolism
»»»»» increased heat production
»»»»» increased body temp. which it is fatal if not treated
Hypothermia
Decreased body temp. »»»»» slow metabolic rate & physiological process (low HR, RR, PB & loss of consciousness)
If temp. below 28C loss of spontaneous return to normal state but if warmed
externally »»»»» individual survive
If care is taken in preventing the formation of ice crystals in tissues, then no damage is produced after subsequent warming
Human can tolerate body temp. of 21-24C during which it is possible to perform open-heart surgery & brain surgery