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Answers to End-of-Chapter Questions – Brooker et al ARIS site
Chapter 47
Test Yourself Questions
1. Hemolymph differs from blood in that it
a. does not contain blood cells.
b. is a mixture of blood and interstitial fluid.
c. circulates through closed circulatory systems only.
d. functions only in defense of the body and not transport.
e. does not pass through the heart.
Answer: b. Hemolymph is the transport fluid of open circulatory systems and is composed of blood and
interstitial fluid.
2. The heart chamber that functions as the receiving chamber is
a. the atrium.
b. the ventricle.
c. the aorta.
d. the pulmonary artery.
e. the coronary artery.
Answer: a. The heart chamber that functions as the receiving chamber is the atrium.
3. Amphibians are unique in that
a. they are the only vertebrates with an open circulatory system.
b. oxygen diffuses into their blood through gills.
c. oxygen diffuses into the blood from the lungs or through the skin.
d. they have a four-chambered heart.
e. none of the above.
Answer: c. Amphibians are unique in that oxygen diffuses into the blood from the lungs or through the skin.
4. A major advantage of a double circulation is
a. blood can be pumped to the upper portions of the body by one circuit and to the lower portions of
the body by the other circuit.
b. each circuit can pump blood with differing pressures to optimize the function of each.
c. the oxygenated blood can mix with the deoxygenated blood before being pumped to the tissues of
the body.
d. less energy is needed to provide nutrients and oxygen to the tissues of the body.
e. all of the above.
Answer: b. A major advantage of a double circulation is each circuit can pump blood with differing pressures to
optimize the function of each.
5.
The function of erythrocytes is to
a.
transport oxygen throughout the body.
b.
defend the body against infection and disease.
c.
transport chemical signals throughout the body.
d.
secrete the proteins that form blood clots.
e.
all of the above.
Answer: a. The function of erythrocytes is to transport oxygen throughout the body.
6.
The mammalian heart is a myogenic heart, meaning
a.
it is composed of four chambers.
b.
it acts as two pumps for two different circulations.
c.
contraction is regulated solely by the nervous system.
d.
contraction is regulated by specialized cells of the heart.
e.
it contains valves that maintain a one-way flow of blood.
Answer: d. The mammalian heart is a myogenic heart meaning contraction is regulated by specialized cells of
the heart.
7. During systole of the cardiac cycle
a.
the ventricles of the heart are relaxed.
b.
the ventricles of the heart are filling.
c.
the ventricles of the heart are contracting.
d.
the atria of the heart are contracting.
e.
both a and b.
Answer: c. During systole of the cardiac cycle, the ventricles of the heart are contracting.
8.
Considering blood flow through a closed circulation, which of the following is the correct sequence of
vessels beginning at the heart?
a.
arteriole, artery, capillary, vein, venule
b.
artery, capillary, arteriole, venule, vein
c.
vein, venule, capillary, arteriole, artery
d.
artery, arteriole, capillary, venule, vein
e.
artery, arteriole, capillary, vein, venule
Answer: d. The correct sequence of vessels, beginning at the heart, is artery, arteriole, capillary, venule, vein.
9.
Gas and nutrient exchange between the circulation and the tissues occurs at
a.
the arteries.
b.
the arterioles.
c.
the capillaries.
d.
the venules.
e.
the veins.
Answer: c. Gas and nutrient exchange between the circulation and the tissues occurs at capillaries.
10.
Which of the following factors determine blood pressure?
a.
cardiac output
b.
resistance
c.
arteriole diameter
d.
all of the above
e.
a and b only
Answer: d. Blood pressure is determined by how hard the heart is working, which determines the cardiac output
and the diameter of arterioles, which alters resistance of blood flow.
Conceptual Questions
1.
What are the three basic components of a true circulatory system?
Answer:
 Blood or hemolymph, an internal body fluid containing dissolved solutes;
 Blood vessels, a system of hollow tubes within the body through which blood travels;
 One or more hearts, muscular structures that pump blood through the blood vessels.
2.
List and briefly explain the components of blood.
Answer:




3.
Plasma is a yellowish solution of water and solutes, making up 35-60% of the total volume of blood in
vertebrates. It transports water and organic and inorganic nutrients absorbed from the digestive tract,
dissolved oxygen, waste products of metabolism like carbon dioxide, and all other molecules produced
by the cells.
Leukocytes or white blood cells of several types defend the body against infection and disease.
Erythrocytes or red blood cells contain hemoglobin and transport oxygen throughout the body.
Platelets play a crucial role in the formation of blood clots.
Explain the cardiac cycle.
Answer: The cardiac cycle can be divided into two phases. The first is diastole, during which the ventricles fill
with blood coming from the atria through the open AV valves. This is followed by systole, the contraction of the
ventricles which ejects blood through the open semilunar valves.
Experimental Questions
1.
What observation did Furchgott make when testing the effects of acetylcholine on different treatments of
rabbit aorta? How did he explain the results?
Answer: Furchgott noted that acetylcholine had different effects on the rabbit aorta depending on the type of
treatment of the rabbit aorta. When applied to flattened strips of the aorta, the acetylcholine caused contraction
of the muscle; however, when applied to circular rings of the aorta, acetylcholine caused relaxation. Furchgott
suggested that the difference was due to the absence of the endothelial layer of tissue in the flattened strips of
aorta.
2.
Based on his observations of the effects of acetylcholine on different preparations of rabbit aorta, what
hypothesis did Furchgott propose to explain the relationship of acetylcholine and vasodilation? How did he test
this hypothesis?
Answer: Furchgott hypothesized that acetylcholine stimulated the endothelial cells to secrete a substance that
functions as a vasodilator, causing the muscle layer to relax. Furchgott performed several experiments to test
his hypothesis. He compared the effects of acetylcholine on circular rings of aorta that either had the
endothelial layer intact or experimentally removed. The results of this experiment demonstrated that when the
endothelial layer was present, relaxation occurred in the presence of acetylcholine. Removal of the endothelial
layer, however, resulted in contraction of muscle in the presence of acetylcholine. In a second experiment, a
strip of the aorta with the endothelial layer removed was put in contact with a strip of aorta with an intact
endothelial layer. When this “sandwiched” treatment was exposed to acetylcholine, both muscle layers relaxed.
3.
What did Furchgott conclude based on his experimental results?
Answer: Furchgott concluded that the endothelial layer produces a vasodilator in the presence of acetylcholine.
The vasodilator diffused from the intact strip of muscle to the denuded strip and caused the muscle layer to
relax.
Collaborative Questions
1. Discuss the difference between a closed and an open circulatory system.
Answer:
Closed circulatory system - In a closed circulatory system, the blood and interstitial fluid is contained within
tubes called blood vessels and is transported by a pump called the heart. All of the nutrients and oxygen that
tissues need must be delivered directly to them by the blood vessels. Due to its efficiency, a closed circulatory
system allows organisms to become larger. Annelids and all vertebrates are examples of animals which have a
closed circulatory system.
Open circulatory system - In an open circulatory system, the organs are bathed in hemolymph instead of it
being delivered to them by blood vessels. Like a closed circulatory system, there is a pump and blood vessels
but these two structures are less developed and less complex compared to a closed circulatory system. Partly
as a result, organisms like mollusks and arthropods are limited to being relatively small.
2. Discuss the types of closed circulatory systems found in vertebrates.
Answer:
Single circulation - This is the type of closed circulatory system found in fish and is the simplest type of
circulation found in vertebrates. In this system, deoxygenated blood from the tissues is returned to the twochambered heart, which then pumps the blood to the gills. In the gills, blood picks up oxygen, then circulates to
the tissues to drop off oxygen and nutrients and pick up carbon dioxide and wastes. Arteries are the blood
vessels which carry blood away from the heart and veins carry blood to the heart.
Double circulation - This is the type of circulatory system found in crocodiles, birds, and mammals, and is
divided into two parts: the systemic and pulmonary circulation. In the systemic circulation, blood is pumped from
the left side of the heart to the body to drop off oxygen and nutrients and pick up carbon dioxide and wastes.
The blood then returns to the right side of the heart. In the pulmonary circulation, the right side of the heart
pumps blood to the lungs to release carbon dioxide and pick up oxygen from the atmosphere. Due to the fact
that the heart is divided into a right and left side it acts as two hearts in one, which increases the efficiency of the
circulation. Amphibians and most reptiles have a circulation with features of both types.