Download Answers to Mastering Concepts Questions

Mastering Concepts
30.1
1. What are the components of a circulatory system?
The components of a circulatory system are a heart, blood (or a similar fluid), and vessels
that transport the blood throughout the body.
2. Distinguish between open and closed circulatory systems.
Open circulatory systems lack a continuous circuit of vessels. The heart pumps fluid
through short vessels that empty into open areas in the body where materials are
exchanged with surrounding cells; the fluid returns to the heart through pores. In a closed
system, blood remains within a continuous network of vessels, and nutrients are
exchanged with the tissues across the vessel walls.
3. Describe the circulatory systems of fishes, nonavian reptiles, and mammals. What is
the advantage of separating the pulmonary and systemic circulatory pathways?
Fishes have one circulatory pathway with a two-chambered heart. Nonavian reptiles
have a pulmonary and systemic circulatory pathway, but these pathways share a ventricle
where oxygenated and deoxygenated blood mix. Mammals have two separate circulation
pathways (one for the lungs and one for the rest of the body). Separating the pulmonary
and systemic circulatory pathways boosts efficiency in energy-hungry endotherms
(mammals and birds) because O2-rich blood does not mix with O2-depleted blood in the
heart as it does in other types of vertebrates.
30.2
1. What are the components of blood?
Blood contains plasma, red blood cells, white blood cells, and platelets.
2. Referring to figure 30.4, speculate about which blood type is considered the “universal
donor” and which is called the “universal recipient.” Explain your answer.
A person with type O blood is considered a “universal donor” because people with any
blood group can receive type O blood. A person with type AB blood is a “universal
recipient” because he or she can receive transfusions of any blood type.
30.3
1. What is the cardiovascular system?
The cardiovascular system is the transportation network consisting of the heart, blood,
and blood vessels.
2. Describe the relationship among arteries, veins, arterioles, venules, and capillaries.
Arteries are the major vessels that carry blood away from the heart; they branch into the
smaller arterioles, which become the network of capillaries where materials are
exchanged between the blood and tissues. The capillaries rejoin to form the venules,
which become the larger veins that return blood to the heart.
30.4
1. Trace the pathway of an O2 molecule from the lungs to a respiring cell at the tip of
your finger.
At the lungs, hemoglobin in red blood cells binds to O2. The blood travels to the heart by
way of the pulmonary vein and enters the left atrium. The blood is then sent to the left
ventricle, where it is pumped out into systemic circulation. It passes through many
arteries and arterioles until it reaches its destination, a respiring cell at the tip of the
finger. The O2 then diffuses out of the capillary bed, into the interstitial fluid, and into
the respiring cell.
2. Why is the heart sometimes called “two hearts that beat in unison”?
The “two hearts” are the right and left sides of the heart. The right side delivers
deoxygenated blood to the lungs, and the left side delivers the oxygenated blood to the
rest of the body.
3. How does a heartbeat originate and spread?
The heartbeat originates in the sinoatrial node. It spreads across the atria to the
atrioventricular node, which sends an electrical signal to the ventricle walls.
30.5
1. Compare and contrast the structures of arteries, capillaries, and veins.
Arteries, capillaries, and veins are all blood vessels; all have an inner layer of endothelial
cells. Capillaries are the smallest vessels, consisting of only a single layer of endothelial
cells. Arteries and veins are much larger and differ in their functions, the thickness of
their layer of smooth muscle tissue, and in internal specializations. Arteries take blood
away from the heart, whereas veins bring blood to the heart. Arteries have a thicker wall
of smooth muscle than do veins. Large and medium-sized veins of the legs have venous
valves that prevent backflow of blood. When muscles squeeze on veins they help return
blood to the heart. The force of heart contractions moves blood in arteries.
2. Explain why blood pressure is highest in the arteries and lowest in the veins.
Pressure on the arteries is high due to their close proximity to the heart, which pumps
blood directly to the arteries. The farther an artery is from the heart, the lower the
pressure. Once the blood reaches the veins, the heart contributes little or nothing to blood
movement. Instead, skeletal muscle contraction propels blood back to the heart; therefore,
the pressure in veins is low.
3. How is the regulation of blood pressure an example of negative feedback?
In negative feedback, the body responds to a change by taking action to counteract the
change. For example, when blood pressure is too high, arterioles in the skin dilate and the
heart rate slows; these actions decrease blood pressure. In contrast, if blood pressure is
too low, arterioles in the skin constrict and the heart rate increases, boosting blood
pressure.
30.6
1. Where does lymph come from?
Lymph is blood plasma that leaks out of capillaries.
2. List the functions of each component of the lymphatic system.
Lymph capillaries absorb lymphatic fluid from tissues and send it to lymph nodes, which
contain white blood cells that remove foreign cells and tissue debris from the fluid.
Eventually, lymph vessels empty lymphatic fluid into the bloodstream in veins in the
chest. The spleen is an organ of the lymphatic system that releases white blood cells. T
cells mature in the thymus.
3. How does lymph travel within lymph capillaries?
Lymph is pushed through lymph capillaries when the surrounding skeletal muscles
contract.
30.7
1. How did researchers use DNA evidence to determine why icefishes have colorless
blood?
Researchers sequenced DNA encoding globin proteins from 33 Antarctic fish species.
Red-blooded fish species had intact alpha and beta globin genes. In most icefish species,
however, the entire beta globin gene and most of the alpha globin gene was missing; one
icefish had mutated alpha and beta globin genes. The researchers therefore concluded that
icefishes have colorless blood because they cannot make hemoglobin.
2. Which component of blood is likely to transport most of the oxygen in an icefish?
Most of the oxygen is probably dissolved in the blood plasma.
Write It Out
1. How are open and closed circulatory systems similar? How are they different?
Open and closed circulatory systems circulate blood (or a comparable fluid) throughout
an animal’s body. In an open circulatory system, the fluid directly bathes the body’s cells,
whereas in a closed circulatory system, the blood remains confined to vessels and does
not come into direct contact with the body’s cells.
2. Some athletes turn to blood doping to gain an unfair competitive advantage. For
example, they make take supplements of erythropoietin (EPO), a hormone that stimulates
red blood cell production. Why would increasing the number of circulating red blood
cells help an athlete? What might be the dangers of having too many red blood cells?
Red blood cells carry O2 needed for respiration in muscles and other body tissues. Since
blood doping increases the production of red blood cells, the blood of athletes that cheat
with EPO supplements can carry extra O2. However, blood doping has possibly
dangerous consequences. If too many red blood cells are produced, then blood becomes
thicker, which raises blood pressure. The chance of a heart attack or stroke therefore
increases after blood doping.
3. People infected with HIV eventually develop a diminished white blood cell count.
When examining a blood sample under the microscope, would the blood cell composition
of an AIDS patient look different from that of an unaffected individual? Why or why not?
[Hint: consult figure 30.3.]
According to figure 30.3, white blood cells make up a tiny fraction of the cells in blood.
The blood of an AIDS patient would therefore not appear much different under the
microscope from that of an unaffected individual. Physicians must use techniques other
than microscopy to test for HIV.
4. Describe the process of blood clotting.
Blood forms clots shortly after blood to escapes from a vessel through a wound. As the
vessel constricts, platelets adhere to the wounded area, forming a plug that helps control
blood loss. In the meantime, exposure of blood to the surrounding tissue activates
clotting factors that trigger clot formation.
5. One effect of aspirin is to prevent platelets from sticking together. Why do some
people take low doses of aspirin to help prevent a heart attack?
A heart attack is caused by a blocked coronary artery. When the platelets don’t easily
stick together, blockages are less likely to occur.
6. Describe the path of blood through the heart’s chambers and valves, and through the
pulmonary and systemic circulations.
Blood flows along this pathway: right atrium, right AV valve, right ventricle, semilunar
valve, to the lungs via the pulmonary artery, to the capillaries of the lungs, and then back
to the heart via the pulmonary veins. The pulmonary veins empty into the left atrium,
from which blood passes through the left AV valve, left ventricle, semilunar valve, and
then to the body tissues via the aorta.
7. Describe the events that occur during one cardiac cycle.
The heart contracts and relaxes in one cardiac cycle. The initial signal to contract comes
from the sinoatrial (SA) node in the right atrium; this signal triggers contraction of both
atria. The electrical signal is briefly delayed at the AV node, giving the ventricles time to
fill. Lastly the electrical signal spreads through both ventricles and they contract,
pushing blood out of the heart.
8. Why does the heart rate increase during exercise? Why does regular exercise decrease
the resting heart rate?
Exercise requires lots of ATP. The body must quickly produce ATP by aerobic
respiration, increasing the tissues’ demand for O2. The blood delivers O2 to the tissues, so
during exercise blood must flow through the system more quickly; the body increases
cardiac output by increasing the heart rate. Over time, regular exercise strengthens the
heart, increasing stroke volume and cardiac output. As a result, the heart delivers the
same volume of blood with fewer beats during rest.
9. Draw a diagram that compares systemic arteries, capillaries, and systemic veins in
terms of cross-sectional area, blood pressure, blood velocity, and O2 content of blood.
Figure 30.14 shows how cross-sectional area, blood pressure, and blood velocity vary
among arteries, capillaries, and veins. A line showing the O2 content of blood should
show that the O2 concentration is highest in arteries, drops quickly in capillaries as O2 is
delivered to tissues, and remains low in veins.
10. Endothelial cells lining the heart and blood vessels are the only cells to receive
nutrients and O2 directly from blood. How do the rest of the body’s cells receive these
resources and dispose of wastes?
Nutrients and O2 diffuse across capillary walls from blood to the interstitial fluid
surrounding cells to the body’s cells. CO2 and other metabolic wastes diffuse in the
opposite direction.
11. Explain why a doctor listens at your inner elbow with a stethoscope when measuring
your blood pressure.
The stethoscope allows the doctor to listen to blood flowing through an artery in your
arm. The blood pressure cuff is inflated to a pressure that cuts off blood flow through the
artery. The doctor slowly decreases the pressure in the cuff until he or she hears blood
again. The first sound of blood flow is the systolic pressure—the pressure in the artery
when the heart’s ventricles contract. He or she decreases the pressure in the cuff further,
until the sound stops, indicating that the cuff pressure is lower than the pressure in artery.
The pressure when the sound of the pulse ends is the diastolic pressure.
12. What types of changes in blood vessels would raise blood pressure?
Anything that causes blood vessels to become narrower – from drugs to the buildup of fat
in arteries – would raise blood pressure.
13. The carotid artery extends from the heart to the head. Some of the body’s blood
pressure receptors are located in the carotid sinus, where the carotid artery passes through
the neck. If you press lightly on the carotid sinus, what do you predict should happen to
your heart rate? What if you press lightly on a spot just below the carotid sinus? Hint:
Figure 30.15 may help you answer this question.
Light pressure on the carotid sinus would cause the receptors to sense an increase in
pressure. This will cause the heart rate to fall to counter the perceived rise in pressure.
The resulting drop in blood pressure could actually cause a person to pass out. If you
press just below the sinus, then less blood will enter the sinus and a drop in pressure will
be detected. This will result in an increase in heart rate to compensate.
14. Where does lymph originate? What propels lymph through the lymphatic vessels?
How is the lymphatic system connected with the circulatory system? The immune
system?
Lymph begins as interstitial fluid that has leaked from blood capillaries. It is picked up in
lymph capillaries and is propelled through the body by skeletal muscle contraction.
Lymph eventually empties into veins in the chest, where it is returned to the circulatory
system. Along the way, the lymph passes through lymph nodes, which contain many
immune system cells that fight infection.
15. Describe the interactions between the circulatory system and the respiratory, immune,
digestive, and endocrine systems.
Blood passing through the respiratory system disposes of waste CO2 and picks up O2 to
deliver to the tissues. White blood cells are immune system cells that are carried
throughout the body in blood. Blood passing near the digestive system picks up nutrients
and carries them to the body’s cells. The endocrine system secretes hormones that are
carried in the bloodstream.
16. Name three ways that the circulatory system helps maintain homeostasis.
(1) The circulatory system delivers O2 for cells to use in aerobic respiration, which
restores depleted ATP. (2) The circulatory system removes wastes from the cells,
preventing the buildup of harmful products. (3) Hormones circulate in the bloodstream
and maintain homeostasis in many ways.
17. How is the human cardiovascular system similar to and different from the vascular
tissue in a plant?
Both the human cardiovascular system and a plant’s vascular tissues deliver water,
nutrients, and hormones to cells. However, the human cardiovascular system is a circuit
of vessels linked to a pump; a plant vascular system lacks a pump, and the vessels do not
form a closed circuit. The cell types are differ between humans and plants as well.
18. Use the Internet to learn more about disorders of the cardiovascular or lymphatic
system. Choose one to investigate in more detail. What causes the disease you chose?
Who is affected, and what are the consequences? Are there ways to prevent, treat, or cure
the disease?
[Answers will vary.]
Pull It Together
1. How do pulmonary and systemic circulation fit into this concept map?
“Heart” connects with the phrase “delivers blood to lungs via the” to “Pulmonary
circulation.” “Heart” connects with the phrase “delivers blood to the body via the”
“Systemic circulation.”
2. Write the relative percentages (by volume) of cells, platelets, and plasma into the
boxes for these terms.
Refer to figure 30.3. Plasma makes up approximately 55% of blood volume. The
remaining 45% is made of cells and cell fragments (platelets). Of this portion, 95.2%
consists of cells and 4.8% comes from platelets. Cells therefore make up about 43% of
blood volume (0.45 times 0.952 equals 0.43) and platelets make up the other 2% (0.45
times 0.048 equals 0.02).
3. Connect red blood cells and white blood cells with lymph capillaries and the three
types of blood vessels, using phrases that indicate whether each cell type typically occurs
in each vessel.
“Red blood cells” leads with the phrase “occur in” to “Arteries,” “Capillaries,” and
“Veins.” “Red blood cells” leads with the phrase “do not typically occur in” to “Lymph
capillaries.” “White blood cells” leads with the phrase “occur in” to “Arteries,”
“Capillaries,” “Veins,” and “Lymph capillaries.”