Final answer:
Newborns struggle with thermoregulation due to their higher surface area to volume ratio, thin layer of subcutaneous fat for poor insulation, and immature musculature and nervous system, which limit heat generation and conservation. However, they utilize nonshivering thermogenesis through brown adipose tissue to generate heat.
Step-by-step explanation:
The difficulty in thermoregulation that a newborn encounters primarily stems from their physiological characteristics and the adjustments they must make after leaving the womb. One of the significant factors is that newborns have a higher ratio of surface area to volume than adults, meaning they lose heat more rapidly and have less volume to generate warmth. Furthermore, newborns possess a relatively thin layer of subcutaneous fat that provides insufficient insulation, compounded by their immature musculature which limits their ability to shiver and generate heat. Lastly, the underdeveloped nervous system hinders their capacity to constrict blood vessels in response to cold, adding to their challenges in maintaining body temperature.
In light of these challenges, newborns rely on a special heat generation process called nonshivering thermogenesis, which involves the breakdown of brown adipose tissue, or brown fat. This type of fat, which is different from the more familiar white fat, has a high capacity for generating heat without the need for muscle contractions associated with shivering. It's located over areas such as the back, chest, and shoulders, and plays a critical role in keeping newborns warm.