hypothermia control

 Q: Heat is generated in human body by which set of two organs? (select one) 

A) heart and liver 

B) heart and lungs 

C) liver and lungs 

D) skin and lungs 

 E) skin and heart

Answer: A

Normally, the heat regulation in human body is balanced by four organs. 

• Heat production = heart and liver (ongoing cellular metabolism) 
• Heat loss = skin and lungs (ongoing evaporation, radiation, conduction, and convection)

The human's capacity to balance the temperature through the above mechanism is very limited. Hypothalamus acts as a mediator to regulate body temperature at 37±0.5°C. In response to cold, hypothalamus takes over the system! and stimulates heat production. The overt obvious mechanism is to induce shivering. Covertly it increases thyroid, catecholamine, and adrenal activities. Also, it sympathetically mediates the vasoconstriction to peripheral tissues. 

If the environmental cold persists, shivering declines and stops around 32°C. At this point, human metabolism (production) and cardiac output start to cease.

#hypothermia

References:

1. Hanania NA, Zimmerman JL. Accidental hypothermia. Crit Care Clin 1999; 15:235. 

2. Lee-Chiong TL Jr, Stitt JT. Disorders of temperature regulation. Compr Ther 1995; 21:697. 

3. Brown DJ, Brugger H, Boyd J, Paal P. Accidental hypothermia. N Engl J Med 2012; 367:1930.