Final answer:
Brown adipose tissue is the primary stimulator of non-shivering thermogenesis in infants, helping to maintain body temperature by breaking down fat to produce heat. This process is particularly crucial in newborns who lack a fully developed shivering mechanism and are prone to faster heat loss due to their body proportions.
Step-by-step explanation:
The stimulators of non-shivering thermogenesis in infants include brown adipose tissue and certain neural mechanisms. In infants, brown adipose tissue, which is found on the neck and along the back, plays a significant role in maintaining body temperature. This type of fat is different from the more common white adipose tissue found in adults as it contains a high number of mitochondria, whose main function is to facilitate the breakdown of fat to produce heat instead of ATP. This brown fat thermogenesis is essential in infants, who do not have the shivering mechanism well-developed and also possess a higher surface area to body mass ratio, contributing to increased heat loss.
During fetal development, the placenta helps to accumulate brown fat by secreting inhibitors that prevent its metabolism. Once an infant is exposed to cold, these stores of brown fat are mobilized to generate heat and regulate the infant's temperature. This process of breaking down brown adipose tissue to produce heat is known as the nonshivering thermogenesis process and is critical for newborns to maintain their body heat. Factors such as increased insulin levels and a reduced metabolic rate are not direct stimulators or inhibitors of this process in infants. Instead, brown adipose tissue and its controlled breakdown by neural mechanisms are the primary factors.