Download 3.9 Answers

SECTION 3.9 QUESTIONS
(Page 202)
Understanding Concepts
1. The circulatory system brings oxygen and nutrients to cells; takes wastes away from cells; relays chemical
messages
throughout the body; and helps maintain acceptable levels of fluids. The circulatory system is also important in the
body’s immune system and permits the transport of immune cells throughout the body.
2. The circulatory system includes the heart, blood vessels, and the blood. The cardiovascular system (cardio
referring
to the heart, and vascular referring to vessels) includes only the heart and blood vessels.
3. Assuming that the average human lifespan is 76 years and assuming an average heart rate of 72 beats per min,
the heart
beats approximately 2 876 083 200 times in a lifetime.
72 beats/min 60 min/h 24 h/d 365 d/y 76 y/lifetime 2 876 083 200 beats/lifetime
98 U nit 3 Student Book Solutions NEL
The cause of eating disorders such as anorexia nervosa
and bulimia is unknown.
Anorexia nervosa is not a new disease; it was first identified
in 1669, and most commonly after 1873. In neither
period was thinness seen as desirable. Bulimia was
identified in the ancient Greeks.
Eating is controlled by many factors, including appetite,
food availability, family, peers, and cultural practices.
Low self-esteem, feelings of helplessness, and the need
to exert control over some aspect of life may all play as
large a role in eating disorders as desire for thinness.
If an eating disorder runs in the family that may also be
a main cause.
Several family and twin studies suggest a high inheritability
of anorexia and bulimia. Researchers suspect
that multiple genes may interact with environmental and
other factors to increase the risk of developing these
disorders.
Gonadal steroids may play a role in eating disorders,
considering their emergence at puberty or soon after,
and the increased risk for eating disorders among girls
with early onset of menstruation.
4. If the blood vessel is connected directly to the left or right atrium it is a vein because the atria receive the blood
as it
returns from the lungs and the body. If the blood vessel is connected directly to the left or right ventricle then it is
an
artery because the ventricles pump blood from the heart to the lungs and to the body. Arteries carry blood from the
heart to the body and lungs; veins carry blood from the body and the lungs to the heart. Arteries tend to have more
elastic tissue and are able to withstand greater pressure. Lower-pressure veins have a thinner middle layer. Arteries
tend to have thicker walls, and a more rounded appearance in cross section. Veins tend to have thinner walls, and a
more squashed appearance in cross section (see Figure 6, page 199 in the Student Text).
5. The pulmonary circuit carries deoxygenated blood to the lungs and oxygenated blood back to the heart. The
systemic
circuit carries oxygenated blood to the tissues of the body and deoxygenated blood back to the heart. The two
circuits
are interconnected in the heart and work together to ensure that the body is supplied with oxygenated blood. The
oxygenated blood that comes back to the left atrium of heart from the lungs then flows into the left ventricle that
pumps
it to the body. The deoxygenated blood that comes back to the right atrium from the body passes into the right
ventricle
that pumps it to the lungs to pick up a fresh supply of oxygen.
6.
7. Systolic pressure is the blood pressure during the contraction of the ventricles. It is the pressure on the gauge of
a
sphygmomanometer when the first sound is heard. Normal systolic pressure for young adults is 120 mm Hg.
Diastolic
pressure is the blood pressure on an artery when the ventricles are relaxed. It is the pressure on the gauge of the
sphygmomanometer
when the sound is no longer heard. Normal diastolic pressure for young adults is 80 mm Hg.
8. Human and fish circulatory systems are both closed systems. The human heart has four pumping chambers. The
fish
heart has four chambers, two of which are true pumping chambers. The human circulatory system is divided into
two
circuits—the pulmonary and the systemic. The pulmonary part of the system circulates blood to the lungs where it
picks up oxygen. The systemic part circulates it to the rest of the body delivering oxygenated blood to cells, tissues,
and organs. The fish circulatory system is one continuous circuit. As the blood passes through the gills it absorbs
oxygen from the water flowing over the gills. Each is most efficient for its organisms needs. Humans have a higher
metabolic demand (at least in part because they are homeothermic) for oxygen, and thus, require separate
pulmonary
and systemic systems. Fish have a lower metabolic demand, and thus require a simpler system. Overall, the human
system is more efficient at delivering oxygen to tissues.
Applying Inquiry Skills
9. Since leukemia, like other cancers, causes rapid and uncontrolled cell division, Subject B might be suffering
from
leukemia. Increased white blood cell numbers can be seen compared with the normal amount.
NEL Section 3.9 99
pulmonary vein
pulmonary artery
left atrium
left ventricle
vena cava
right ventricle
deoxygenated blood oxygenated blood
aorta
body cells
right atrium
lungs
Making Connections
10. Because blood is removed, the body begins producing more red blood cells to replace the loss. When the
removed red
blood cells are returned to the body, oxygen-carrying capacity will be increased. However, some problems may
result.
The greater number of red blood cells means that the fluid-to-cell ratio of the blood will be lower and, therefore,
more
difficult to pump. The increased viscosity will place added strain on the heart. The red blood cells also present a
problem when they begin to break down, because the heme component of the hemoglobin is toxic.