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This chapter explores the circulation and gas exchange systems in arthropods, insects, and amphibians. Topics covered include the fluid movement in the circulatory system, the advantages of open circulatory systems in insects, the differences between two-chambered and three-chambered hearts, the mechanisms of contraction in atrial cells, the ability of a heart to beat after removal, the filtration and reabsorption of fluid in capillaries, the role of erythropoietin hormone in erythrocyte production, the efficiency of concurrent and countercurrent flow in exchange, and the minor physiological importance of CO2 and O2 exchange in certain organisms.
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Chapter 42 Circulation and Gas Exchange Questions prepared by Ruth BuskirkUniversity of Texas at Austin John LepriUniversity of North Carolina, Greensboro
The fluid that moves around in the circulatory system of a typical arthropod is • a) the intracellular fluid. • b) the interstitial fluid. • c) the blood plasma. • d) the digestive juices. • e) the cytosol.
Compared to other organisms with closed circulatory systems, the open circulatory system of insects • expends more energy to pump exchange materials. • exchanges CO2 and O2 directly with the environment. • independently regulates the distribution of exchange material to each organ in the body. • is possible only in organisms with rigid exoskeletons. • allows fluids to move freely in and out of vessels.
An adaptive advantage of having a three-chambered heart, as found in amphibians, over the two-chambered heart of fish is that • there are capillary beds in both the respiratory organ and body systems of amphibians but not fish. • the additional chamber in the amphibian heart reduces blood flow to the respiratory organ. • fully oxygenated blood returning to the amphibian heart can undergo additional pumping to reach higher pressures. • fully oxygenated blood is kept completely separate from relatively deoxygenated blood in the heart. • amphibians can tolerate higher environmental pressures.
The normal contraction of specialized atrial cells results from the activity of the _______, and the simultaneous contraction of the left and right atria is due to the ________. • autorhythmic pacemaker cells; autorhythmic pacemaker cells • gap junctions; gap junctions • autonomic nervous system; somatic nervous system • autorhythmic pacemaker cells; gap junctions • gap junctions; autorhythmic pacemaker cells
As in Edgar Allan Poe’s short story “TheTell-Tale Heart,” a heart can continue to beat after it is removed from the body, because • pacemaker cells contract without input. • nerves in the heart fire without input. • hormones controlling heartbeat are released spontaneously. • powerful ventricular contractions induce rebound contractions. • pulsing of blood in the heart maintains the heartbeat.
Fluid is filtered from blood as it enters a capillary due to the______ , but fluid is reabsorbed as the blood exits a capillary due to the _______. • hydrostatic pressure from smooth muscle; cooler temperatures in venous blood • osmotic pressure due to high levels of sodium in plasma but not extracellular fluid; osmotic pressure due to reversed levels of sodium in extracellular fluid but not plasma • hydrostatic pressure from the heart; osmotic pressure from proteins in the plasma • osmotic pressure from salts; hydrostatic pressure from the veins
In response to a period of abnormally low O2 in circulating blood, the _______ secrete(s) the hormone erythropoietin (EPO), thus stimulating erythrocyte production in the _______. • kidneys; bone marrow • liver; spleen • anterior pituitary gland; liver • hypothalamus; thymus • pancreas; gall bladder
Concurrent flow is not as efficient in exchange as countercurrent flow because the latter provides • more diffusion at the beginning of capillary flow than midway through the capillary. • more diffusion at the end of capillary flow than midway through the capillary. • adequate diffusion of gases across weaker concentration gradients. • thinner capillary walls to promote diffusion. • greater surface area for diffusion.
The exchange of CO2 and O2 across ________ is of only minor physiological importance to the organismal homeostasis of metabolic gases. • frog skin • fish gill membranes • insect tracheal tubules • bird air sac membranes • human alveolar membranes
Fully oxygenated hemoglobin arriving in capillaries near active muscles, where PO2 is about 40 mm Hg, would likely “unload” ______ of its O2 at that point. • 10% • 30% • 50% • 70% • 90%
At PO2 of about 40 mm Hg, and under conditions of increased acidity in the blood, the percent oxygen saturation of hemoglobin will be closest to • 10%. • 30%. • 50%. • 70%. • 90%.
