As stated above, the resistance to asphyxia in the fetus and newborn is lost shortly after birth (Table 3.17). The actual degree of of resistance is dependent upon whether the species is precocious or altricial.
Precocious young (e.g. guinea pig) show reduced resistance, whereas altricial young (e.g. rat, mouse) show a higher resistance.
In general, resistance is less when the circulatory system is rendered non-functional, indicating that blood circulation is contributory. Resistance increases with decreasing body temperature, since lowered temperature decreases metabolism and the need for oxygen. Resistance is at least partially dependent upon stored carbohydrate such as glycogen in the tissues, especially in the heart.
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