• Homeostasis is the stable internal environment that is maintained within the body. • Organisms maintain homeostasis by balancing each of the following factors: · nutrients · wastes · temperature · the immune system · reproductive cycles • A countercurrent exchange system involves the opposite flow of adjacent fluids in order to maximize rates of transfer between the two fluid systems. • The bluefin tuna maintains its body temperature through the use of a countercurrent exchange system.

countercurrent exchange system

- In a countercurrent exchange system, fluids flow in opposite directions. Notice in the diagram to the left that a hot fluid enters the upper vessel while cooler fluid enters the lower vessel. As heat is transferred from the warm vessel to the cool vessel, the warm vessel loses heat and the temperature goes down. - As heat flows into the cool vessel, the temperature rises. Since the fluids are flowing in opposite directions, heat transfer is maximized and what entered as cool fluid becomes much warmer. - The diagram to the left shows two adjacent fluid systems flowing in the same direction. As the fluids travel, heat from the top vessel transfers to the colder fluid. As heat is transferred, the temperature of the liquid in the top vessel goes down, while the temperature of the liquid in the bottom tube goes up. Eventually the two fluids reach an equilibrium temperature, and heat flow between the two liquids ends. - This is NOT an example of countercurrent exchange. Countercurrent exchange allows an animal to maximize transfers between adjacent fluids rather than causing transfers to stop.

- The bluefin tuna, an endothermic fish, is able to maintain a constant body temperature through the use of a countercurrent exchange system. - Cool water passes through the gills, causing blood vessels in the gills to lose heat. Vessels carrying cooled blood flow in toward the body and are heated by adjacent vessels carrying heated blood out towards the gills in a countercurrent exchange system.

The disadvantage in heat exchange for adjacent fluids moving in the same direction is that

- once the gradient has disappeared, no further transfer can take place

Countercurrent exchange is

- exchanging a component quantity (like heat) between two fluids with opposing flows

- the maintenance of a stable internal environment.

12.1.1 Animal Homeostasis Flashcards by Irina Soloshenko

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12.1.1 Animal Homeostasis Flashcards

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