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Non-shivering thermogenesis is regulated mainly by thyroid hormone and the sympathetic nervous system. Some hormones, such as norepinephrine and leptin , may stimulate thermogenesis by activating the sympathetic nervous system.
However, brown adipose tissue is highly specialized for this non-shivering thermogenesis. First, each cell has a higher number of mitochondria compared to more typical cells. Second, these mitochondria have a higher-than-normal concentration of thermogenin in the inner membrane.
The UCP1, or thermogenin, gene likely arose in an ancestor of modern vertebrates, but did not initially allow for our vertebrate ancestor to use non-shivering thermogenesis for warmth. It wasn't until heat generation was adaptively selected for in placental mammal descendants of this common ancestor that UCP1 evolved its current function in ...
Both processes consume energy, however high-intensity shivering uses glucose as a fuel source and low-intensity tends to use fats. This is a primary reason why animals store up food in the winter. [citation needed] Brown adipocytes are also capable of producing heat via a process called non-shivering thermogenesis. In this process ...
UCPs contain the three homologous protein domains of MACPs. Although it was originally thought to play a role in non-shivering thermogenesis, obesity, diabetes and atherosclerosis, it now appears that the main function of UCP2 is the control of mitochondria-derived reactive oxygen species. [8] Chromosomal order is 5'-UCP3-UCP2-3'. [9]
The second is non-shivering, which occurs in brown adipose tissue. [19] Population studies have shown that the San tribe of Southern Africa and the Sandawe of Eastern Africa have reduced shivering thermogenesis in the cold, and poor cold-induced vasodilation in fingers and toes compared to that of Caucasians. [5]
Additionally, almost all eutherian mammals (with the only known exception being swine) have brown adipose tissue whose mitochondria are capable of non-shivering thermogenesis. [8] This process involves the direct dissipation of the mitochondrial gradient as heat via an uncoupling protein , thereby "uncoupling" the gradient from its usual ...
In horses, the lower critical temperature is 5 °C while the upper critical temperature depends on the definition used. [11] Their thermoneutral zone is roughly 5–30 °C (41–86 °F). [12] In mice, the lower critical temperature and upper critical temperature can be the same, creating a thermoneutral point instead of a thermoneutral zone.