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The low demands of thermogenesis mean that free fatty acids draw, for the most part, on lipolysis as the method of energy production. A comprehensive list of human and mouse genes regulating cold-induced thermogenesis (CIT) in living animals or tissue samples has been assembled [15] and is available in CITGeneDB. [16]
The human body has two methods of thermogenesis, which produces heat to raise the core body temperature. The first is shivering, which occurs in an unclothed person when the ambient air temperature is under 25 °C (77 °F) [dubious – discuss]. [18] It is limited by the amount of glycogen available in the body. [5]
As in other mammals, human thermoregulation is an important aspect of homeostasis. In thermoregulation, body heat is generated mostly in the deep organs, especially the liver, brain, and heart, and in contraction of skeletal muscles. [1] Humans have been able to adapt to a great diversity of climates, including hot humid and hot arid.
The energetic requirements of a body are composed of the basal metabolic rate (BMR) and the physical activity level (ERAT, exercise-related activity thermogenesis). This caloric requirement can be met with protein, fat, carbohydrates, or a mixture of those. Glucose is the general metabolic fuel, and can be metabolized by any cell.
During the termination of thermogenesis, thermogenin is inactivated and residual fatty acids are disposed of through oxidation, allowing the cell to resume its normal energy-conserving state. The Alternating Access Model for UCP1 with H+ as a Substrate. UCP1 is very similar to the ATP/ADP Carrier protein, or Adenine Nucleotide Translocator .
Its primary function is thermoregulation. In addition to heat produced by shivering muscle, brown adipose tissue produces heat by non-shivering thermogenesis. The therapeutic targeting of brown fat for the treatment of human obesity is an active research field. [10] [11]
Shivering (also called shuddering) is a bodily function in response to cold and extreme fear in warm-blooded animals. When the core body temperature drops, the shivering reflex is triggered to maintain homeostasis. Skeletal muscles begin to shake in small movements, creating warmth by expending energy.
Approximately all enzymatic reaction in the human body is thermogenic, which gives rise to the basal metabolic rate. [2] In bodybuilding, athletes wishing to reduce body fat percentage use thermogenics in order to attempt to increase their basal metabolic rate, thereby increasing overall energy expenditure.