Fever---上海交通大学医学院精品课程.pptVIP

Fever Fever Normal body temperature: 37oC (set point，体温调定点) Circadian variation 1o C ：36.3 - 37.2oC Definition of fever: An elevation of core body temperature above the normal range rectal T 0.5oC oral T 0. 5oC axillary T（腋温） Fever Hyperthermia (过热） fever due to a disturbance of thermal regulatory control excessive heat production (e.g. vigorous exercise, a reaction to some anesthetics) decreased dissipation (e.g. dehydration) loss of regulation (injury to the hypothalamic(下丘脑的) regulatory center) Hyperthermia Pathophysiology Body temperature is determined by two opposing processes heat production heat loss They are regulated by the central nervous system Energy in the form of heat is generated by living tissues (thermogenesis 生热作用) Energy may be passively absorbed from the environment and transfer the energy to the surrounding medium Heat production Increased BMR, by varying the level of circulating thyroxine （甲状腺素) ( controlled by hypothalamus 下丘脑) Increased muscle sensitivity (shivering) Heat loss By varying the volume of blood flowing to skin’s surface (100 fold) By vaporization (exocrine sweating) Pathophysiology The body temperature is under control of the preoptic area of the anterior hypothalamus （视前区下丘脑前部） Thermostat （恒温器） It receives input from both central receptors and peripheral receptors Pathophysiology Elevation of body Temperature shivering thermogenesis and dermal vasoconstriction sympathetic (交感神经）outflow Cooling mechanism sweating and dermal vasodilation mixture of sympathetic and parasympathetic pathways Pathophysiology Hypothalamic thermostat Inherent Set Point: 37oC lowest: 4 a.m; peak: 6~10 p.m Fever follow this pattern Factors affect body Temperature exercise menstrual cycle environmental temperature Pathogenesis of fever Pyrogens (致热原） Substan