The Study of Body Function 23- In a negative feedback loop, the effector organ produces
changes that are
a. in the same direction as the change produced by the initial
stimulus.
b. opposite in direction to the change produced by the initial
stimulus.
c. unrelated to the initial stimulus. - A hormone called parathyroid hormone acts to help raise
the blood calcium concentration. According to the principles
of negative feedback, an effective stimulus for parathyroid
hormone secretion would be
a. a fall in blood calcium.
b. a rise in blood calcium. - Which of these consists of dense parallel arrangements of
collagen fibers?
a. skeletal muscle tissue c. tendons
b. nervous tissue d. dermis of the skin - The act of breathing raises the blood oxygen level, lowers
the blood carbon dioxide concentration, and raises the
blood pH. According to the principles of negative feedback,
sensors that regulate breathing should respond to
a. a rise in blood oxygen.
b. a rise in blood pH.
c. a rise in blood carbon dioxide concentration.
d. all of these. - Adult stem cells, such as those in the bone marrow, brain,
or hair follicles, can best be described as ____ ,
whereas embryonic stem cells are described as
____.
a. totipotent; pluripotent
b. pluripotent; multipotent
c. multipotent; pluripotent
d. totipotent; multipotent
Test Your Understanding
- Describe the structure of the various epithelial membranes
and explain how their structures relate to their functions. - Compare bone, blood, and the dermis of the skin in terms of
their similarities. What are the major structural differences
between these tissues?
15. Describe the role of antagonistic negative feedback
processes in the maintenance of homeostasis.
16. Using insulin as an example, explain how the secretion of
a hormone is controlled by the effects of that hormone’s
actions.
17. Describe the steps in the development of pharmaceutical
drugs and evaluate the role of animal research in this
process.
18. Why is Claude Bernard considered the father of modern
physiology? Why is the concept he introduced so important
in physiology and medicine?
Test Your Analytical Ability- What do you think would happen if most of your
physiological regulatory mechanisms were to operate by
positive feedback rather than by negative feedback? Would
life even be possible? - Examine figure 1.5 and determine when the compensatory
physiological responses began to act, and how many minutes
they required to restore the initial set point of blood glucose
concentration. Comment on the importance of quantitative
measurements in physiology. - Why are interactions between the body-fluid compartments
essential for sustaining life? - Suppose a person has collapsed due to a rapid drop in
blood pressure. What would you expect to find regarding
the rate and strength of this person’s pulse? Explain
how this illustrates the principle of negative feedback
regulation. - Give examples of adult stem cells and explain their abilities
and limitations. Why are adult stem cells needed in the
body?
Test Your Quantitative Ability
Suppose body temperature varies between 36.6 8 C and 37.7 8 C
over a period of a few hours (see fig. 1.4 ).- Calculate the set point as the average value.
- Calculate the range of values (lowest to highest).
- Calculate the sensitivity of the negative feedback loop; this
is the deviation from the set point to the lowest (or highest)
value.
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