Biological Science
5th Edition
ISBN: 9780321743671
Author: Scott Freeman
Publisher: PEARSON
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Chapter 42, Problem 12TYU
Summary Introduction
Introduction:
The ability of the body of an organism to maintain the relatively stable internal conditions, in spite of being surrounded by the continuously altering environment is known as homeostasis. The homeostasis in the body is constantly being regulated by various positive and negative feedback mechanisms. Generally, the negative feedback mechanisms control the homeostatic mechanisms. In these systems, the net effect of the response is either reduced or shut off. The output of the system enhances the original disturbance or stimulus and thus, the variable is pushed away from its initial value in positive feedback mechanisms.
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Which of these homeostatic mechanisms in the body are examplesof positive feedback, and which are examples of negative feedback?Why?a. The adrenal glands produce epinephrine in response to a hormone produced by the pituitary gland in times of stress; the pituitary gland senses the epinephrine in the blood and stopsproducing the hormone.b. As the bladder fills with urine, pressure sensors send messagesto the brain with increasing frequency, signaling that the bladdermust be emptied. The more the bladder fills, the more messagesare sent.c. When you drink an excess of water, specialized cells in yourbrain, as well as stretch receptors in your heart, detect theincrease in blood volume. Both signals are transmitted to thekidneys, which increase the production of urine.
Which of the following mechanisms could both be used by the body to increase body temperature if a person forgets a coat on a cold day? A. Superficial blood vessels dilate, and the thyroid decreases metabolism. B. Superficial blood vessels constrict, and the thyroid decreases metabolism. C. Superficial blood vessels dilate, and the thyroid increases metabolism. D. Superficial blood vessels constrict, and the thyroid increases metabolism.
Which of the following is an example of positive feedback?
Select one:
a. Insulin stimulates cells to absorb glucose, which inhibits the release of insulin.
b. Oxytocin causes uterine contractions during childbirth, which causes more oxytocin to be released from the posterior pituitary.
c. The release of thyroxine from the thyroid causes the anterior pituitary to stop releasing TSH.
d. When calcitonin from the thyroid causes blood calcium levels to decrease, PTH is released from the parathyroid to increase blood calcium levels.
Chapter 42 Solutions
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- Which of the following is an example of a normal physiologic process that uses a positive feedback loop? a. blood pressure regulation b. childbirth c. regulation of fluid balance d. temperature regulationarrow_forwardMatch the body temperature control item to the appropriate location in the negative feedback loop. Effector when variable is low Effector when variable is high Control center Sensor Controlled variable A. Muscles for shivering and goosebumps B. Nerves in skin C. Brain D. Sweat glands E. Temperaturearrow_forwardWhich of the following physiologlcal responses is an example of positive feedback? . The body's production of red blood cells, which transport oxygen from the lungs to other organs, is stimulated by low concentrations of oxygen. b. A high concentration of glucose in the blood causes deeper, more rapid breathing, which expels carbon dioxide. C. Pressure of the baby's head near the opening of the uterus stimulates uterine contractions which cause greater pressure against the uterine opening. d. Heightened body temperature induces sweating which disposes of metabolic heat and cools the body.arrow_forward
- In a negative feedback mechanism,a. the output cancels the input.b. there is a fluctuation above and below the average.c. there is self-regulation.d. a regulatory center communicates with other body parts.e. All of these are correct.arrow_forwardThyroid hormone is the primary hormone that regulates body temperature. It does so by a. stimulating muscle contraction. b. increasing the number of Na+/K+ pumps in neurons. c. vasoconstriction of peripheral blood vessels. d. sweating.arrow_forwardndicate whether each of the following statements is true or false. If false, correct the statement or provide a briefexplanation for why it is false.a. Insulin increases the rate of glucose uptake by the tissues.b. Glucagon is the hormone that signals low blood glucose levels.c. The muscles can use glucose, fatty acids and ketone bodies for fuel.d. Epinephrine stimulates breakdown of glycogen in muscles when there is an immediate needfor energy by muscle cells.e. Glucagon stimulates glycogenolysis to maintain the blood glucose concentration.f. With high [carbohydrate] levels, excess glucose (after glycogen storage has reached amaximum) is converted to fat.g. The high potential electrons of NADH enter the respiratory chain at NADH-Q reductase.h. Ubiquinol (QH2) is also the entry point for electrons from NADH of flavoproteins.i. Cytochrome reductase catalyzes the transfer of electrons from cytochrome c to O2.arrow_forward
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- Which of the following statements is True?a. Ectotherms generate most of their body heatmetabolically.b. Ectotherms include birds and mammals.c. Ectotherms experience variable body temperatures.d. Ectotherms are known as “warm-blooded” animals.arrow_forwardTo achieved homeostasis, the nervous system and endocrine system maintain Normal range of the following variables, EXCEPT? a.Blood calcium level b.Hormones in the cell c.Body Temperature d.Amount of water in the bodyarrow_forwardA male has lost blood as a result of a gunshot wound. Even though thebleeding has been stopped, his blood pressure is low and dropping,and his heart rate is elevated. Following a blood transfusion, his bloodpressure increases and his heart rate decreases. Which of the following statement(s) is (are) consistent with these observations?a. Negative-feedback mechanisms can be inadequate without medical intervention.b. The transfusion interrupted a positive-feedback mechanism.c. The increased heart rate after the gunshot wound and before thetransfusion is a result of a positive-feedback mechanism.d. a and be. a, b, and carrow_forward
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