A term newborn delivered in a delivery room maintained at 22 degrees C develops a core temperature of 36.0 degrees C over the first hour despite vigorous movement of all four limbs. The pediatrician notes abundant subscapular fat pad deposition on examination. Which cellular mechanism is the infant's principal defense against this cold stress?
- A Maximal hepatic gluconeogenesis generating metabolic heat
- B Synchronized skeletal muscle contraction driven by the posterior hypothalamic motor center
- C Uncoupling protein 1 mediated heat production in brown adipose tissue ✓
- D Cutaneous vasodilation with countercurrent heat exchange
Correct answer: C. Uncoupling protein 1 mediated heat production in brown adipose tissue
Explanation
Neonates cannot shiver effectively in the first days of life, so nonshivering thermogenesis in brown adipose tissue is their main heat source. Sympathetic norepinephrine activates hormone sensitive lipase, releasing free fatty acids that are oxidized locally, while uncoupling protein 1 (thermogenin) dissipates the mitochondrial proton gradient as heat instead of ATP. The rich brown fat depots around the scapulae and mediastinum warm the blood directly. Shivering is poorly developed at birth, which eliminates option B.
Reference: Nelson Textbook of Pediatrics, 21st ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.