Unit D

Module 7 ~ Lesson 3

Countercurrent Heat Exchange

Blood also plays a role in maintaining body temperature. Maintaining body temperature means that your body is balancing heat production with heat loss. This is achieved by a countercurrent heat exchange mechanism. On average, the recognized human core body temperature is 37°C. In the face of extreme exertion, cellular respiration within muscles generates a significantly higher amount of heat than resting muscle tissue.

Due to the high heat capacity of water in plasma, blood can absorb, transport, and release large amounts of thermal energy.


The video on homeostasis at the start of this unit used countercurrent heat exchange and selective vasoconstriction as an example of negative feedback. You can return to that video for a review or watch the video below on temperature regulation.


Read "The Functions of Blood", "Circulation and the Action of Capillaries", and "Blood Disorders" on pages 284 to 289 of your textbook.


Blood links the circulatory system with other systems by a network of blood vessels. These vessels allow substances to move in and out of the bloodstream to be transported to other parts of the body or to the external environment.
Factors that can trigger vasoconstriction are high blood pressure, drugs, and cold weather. Factors that can trigger vasodilation are physical exertion, low blood pressure, and drugs/chemicals such as caffeine.