Module 8 Intro
1. Module 8 Intro
1.22. Page 7
Module 8—Circulation, Immunity, and Excretion
Read
Homeostatic Regulation
countercurrent heat exchange: a mechanism used to transfer heat from one flowing current of fluid to another across a semi-permeable membrane
Birds use countercurrent heat exchange between blood vessels in their legs to keep heat concentrated within their bodies.
vasoconstriction: the constriction of blood vessels resulting from muscular contraction in blood vessel walls
When blood vessels constrict, the flow of blood is restricted or slowed. It is the opposite of vasodilation, the widening of blood vessels.
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. It can be 10 to 20 times more in some circumstances.
How does your body cope? Because plasma is mostly water, it has the capacity to absorb and release large amounts of thermal energy. (Remember specific heat capacity from Science 10.)
Watch and Listen
This animation illustrates peripheral heat loss, countercurrent heat exchange, and selective vasoconstriction. You may want to first read “Homeostatic Regulation” on pages 286 and 287 of the textbook.
Self-Check
SC 2. How does blood link the circulatory system with other systems?
SC 3. Name three factors that can trigger vasoconstriction or vasodilation.
Self-Check Answers
SC 2. 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.
SC 3. Factors that can trigger vasoconstriction are high blood pressure, drugs, and cold weather. Factors that can trigger vasodialation are physical exertion, low blood pressure, and drugs/chemicals such as caffeine.
Try This
TR 1. The Body’s Response to Temperature Change
Thermoregulation is the term used when biological systems attempt to maintain temperature. After watching the previous animations and reading the textbook, prepare a summary table. Outline the body’s thermoregulatory response to
- an increase in internal temperature due to exertion
- a colder external temperature than body temperature
Explain how peripheral heat loss, selective vasoconstriction, vasodilation, and countercurrent heat exchange are involved in each circumstance.
Record your responses/summary table in the Lesson 3 Assignment.