Summary OCR A-Level Biology 5.1.4 Temperature Control in Endotherms

Endotherms
Endotherm – an organism that uses heat from metabolic reactions to maintain body
temperature

Advantages of Endothermy
 Maintain a constant body temperature regardless of external conditions
 Remain active even when external temperatures are low, allowing them to escape
potential predators or take advantage of prey that may be available
 Able to inhabit colder parts of the planet



Disadvantages of Endothermy
 Use a significant portion of their energy intake to maintain body temperature and less
for growth
 Require more food
 May overheat in hot weather



Temperature Regulation
 Thermoreceptors in the hypothalamus detect the change in core body temperature
 Hypothalamus will send signals using the neuronal and hormonal communications
systems
 Negative feedback is used to return the body temperature to the optimum
 Thermoregulatory centre on hypothalamus detects change in core body temperature by
monitoring blood temperature while peripheral receptors in the skin can inform the
hypothalamus of changes to temperature in the extremities as an early warning system,
allowing the hypothalamus to act before core body temperature drops



Precapillary Sphincters
 Vasodilation of arterioles and opening of precapillary sphincters directs blood to the
skin surface where more heat can be lost to cool the body down
 Vasoconstriction of arterioles and closing of precapillary sphincters directs blood away
from the skin surface so less heat is lost