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Chapter 16
9. Skin and core temperature are both kept constant in
homeotherms.
10. Leptin inhibits, and ghrelin stimulates appetite.
11. Actively contracting skeletal muscles have an increased need for
insulin.
12. Body mass index is calculated as height in meters divided by
weight in kilograms.
13. In conduction, heat moves from a surface of higher temperature
to one of lower temperature.
14. Skin blood vessels constrict in response to elevated core body
temperature.
15. Evaporative cooling is most effi cient in dry weather.
Chapter 16 Quantitative and Thought Questions
(Answers appear in Appendix A.)
1. What happens to the triglyceride concentrations in the plasma
and in adipose tissue after administration of a drug that blocks
the action of lipoprotein lipase?
2. A resting, unstressed person has increased plasma concentrations
of free fatty acids, glycerol, amino acids, and ketones. What
situations might be responsible and what additional plasma
measurement would distinguish among them?
3. A healthy volunteer is given an injection of insulin. The plasma
concentrations of which hormones increase as a result?
4. If the sympathetic preganglionic fi bers to the adrenal medulla
were cut in an animal, would this eliminate the sympathetically
mediated component of increased gluconeogenesis and lipolysis
during exercise? Explain.
5. A patient with T1DM suffers a broken leg. Would you advise
this person to increase or decrease his insulin dosage?
6. A person has a defect in the ability of her small intestine to
absorb bile salts. What effect will this have on her plasma
cholesterol concentration?
7. A well-trained athlete is found to have a moderately
elevated plasma cholesterol concentration. What additional
measurements would you advise this person to have done?
8. What are the sources of heat loss for a person immersed up to
the neck in a 40°C bath?
9. Lizards can regulate their body temperatures only through
behavioral means. Can you predict what they do when they are
infected with bacteria?
Chapter 16 Answers to Physiological Inquiries
Figure 16–5
Having the transporters already synthesized and
packaged into intracellular vesicle membranes means that
glucose transport can be tightly and quickly coupled with
changes in glucose concentrations in the blood. This protects
the body against the harmful effects of excess blood glucose
levels, and also prevents urinary loss of glucose by keeping the
rate of glucose fi ltration below the maximum rate at which the
kidney can reabsorb it. This tight coupling could not occur if
the transporters needed to be synthesized each time a cell was
stimulated by insulin.
Figure 16–7
The brain is absolutely necessary for immediate
survival, and can maintain glucose uptake from the plasma in
the fasted state when insulin levels are very low.
Figure 16–14
The body’s normal response to leptin is to reduce
appetite and increase metabolic rate. This would not be adaptive
during times when it is important to increase body energy
(fat) stores. An example of such a situation is pregnancy, when
gaining weight in the form of increased fat mass is important
for providing energy to the growing fetus. In nature, another
example is the requirement of hibernating animals to store large
amounts of fat prior to hibernation. In these cases, the effects
of leptin are decreased or ignored by the brain.
Figure 16–15
In the short term, drinking water before a meal
may reduce appetite by stretching the stomach, and this may
contribute to eating a smaller meal. However, as described
in Chapter 15, water is quickly absorbed by the GI tract and
provides no calories, and thus hunger will soon return once the
meal is over.
Figure 16–17
The amount of fl uid in the body decreases as
water evaporates from the surface of the skin. This fl
uid must
be replaced by drinking or the body will become dehydrated.
In addition, sweat is salty (as you may have noticed by the
salt residue remaining on hats or clothing once the sweat has
dried). This means that the body’s salt content also needs
to be restored. This is a good example of how maintaining
homeostasis for one variable (body temperature) may result in
disruption of homeostasis for other variables (water and salt
balance).
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