The right answer is C. cell, tissue, organ, organ system, organism.
The order is increasing from the smallest unit to the entire organism: Cell> Tissue> Organ> organ system> organism.
Take the example of the human being.
The human being is a homeothermic organism, which means that its body temperature is almost constant.
The usual basal body temperature is generally considered to be 37.0 ° C, however this value depends on the location of the body where the measurement is made, the time of day and the activity level of the body. no one. Normal values are between [36 ° C - 37,8 ° C].
The hypothalamus, which contains the thermoregulatory center, receives information from all the thermoreceptors (cutaneous and central); it constantly analyzes the temperature and compares it to a set point (around 37 ° C).
When the body temperature is higher than the set value, the hypothalamus causes the phenomenon of perspiration: the evaporation of sweat causes a lowering of the skin temperature. At the same time, the cutaneous arterioles dilate (increasing the diameter) to promote heat exchanges with the outside.
When the body temperature is below the set point, the hypothalamus activates several thermogenesis mechanisms:
*reduction of heat loss on the body surface: cutaneous vasoconstriction via the sympathetic nervous system (catecholamines act on alpha-1 adrenergic receptors) to reduce thermal exchanges between the skin and the surrounding environment. Goosebumps are also a mechanism of thermogenesis, not very effective in humans because of its low hair growth.
*increase in heat production:
**by the muscular activity: the chills are successions of clonic shaking of the striated musculature providing no mechanical work, all the energy being released in the form of heat;
**by metabolism: catecholamines released by the sympathetic nervous system increase metabolism by lipolysis and glycogenolysis, which induces the production of heat.
