A child shivers in the cold rain yet does not feel cold. The biochemistry involved is:
Newborn babies, infants and young children experience a greater net heat loss than adults because they cannot shiver to maintain body heat. They rely on non-shivering thermogenesis. A child has an increased amount of brown adipose tissue (increased vascular supply and high mitochondrial density), and, when cold-stressed, will have greater oxygen consumption, thereafter releasing norepinephrine. Norepinephrine then reacts with lipases in brown fat to break down fat into triglycerides. Triglycerides are metabolized to glycerol and non-esterified fatty acids. These are further degraded in the needed heat-generating process to form CO2 and water. Chemically, in mitochondria, proton gradient produces the proton electromotive force to synthesize ATP is now bypassed to produce heat directly. So, when a child shivers in the cold rain, he/she does not feel cold.
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