; Chapter 45 Hormones and the Endocrine System
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Chapter 45 Hormones and the Endocrine System

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									                    Chapter 45: Hormones and the Endocrine System

Interactive Questions

45.1 In negative feedback, the response reduces the initial stimulus, thus turning off the
response. In positive feedback, such as in the release of milk during nursing, the stimulus
is reinforced and the response increases.

       a. chemical messages that usually travel through the bloodstream to target cells
       b. chemical messages, such as cytokines, neurotransmitters, NO, growth factors,
       and prostaglandins, that communicate locally between cells
       c. cell that produces hormones
       d. modified nerve cell that produces hormones (neurohormones)

45.3 Oxytocin and ADH are synthesized by neurosecretory cells and transported down
their processes to the posterior pituitary. Releasing and inhibiting tropic hormones are
secreted by neurosecretory cells into capillaries that drain through portal vessels to a
capillary bed in the anterior pituitary.

       a. stimulates contraction of uterus and milk release
       b. increases water reabsorption in kidney
       c. stimulates thyroid gland
       d. stimulate activity of gonads
       e. stimulates adrenal cortex to produce and secrete hormones
       f. various effects, depending on species, including stimulation of milk production
       g. regulates skin pigment cells in amphibians
       h. reduce perception of pain
       i. promotes growth and the release of insulin-like growth factors

45.5 Insufficient iodine results in reduced production of T3 and T4. Thus, there is no
negative feedback to turn off production of TRH by the hypothalamus and TSH by the
anterior pituitary. TSH continues to stimulate the thyroid, which enlarges.

       a. insulin
       b. glucagon
       c. uptake of glucose
       d. glycogen breakdown in liver
       e. islets of Langerhans in pancreas
       f. glycogen hydrolysis in liver and glucose release
       g. blood glucose level
        a. Nervous stimulation from the hypothalamus to the adrenal medulla causes the
        secretion of epinephrine, which increases blood pressure, rate, and volume of
        heart beat, breathing rate, and metabolic rate, stimulates glycogen hydrolysis and
        fatty acid release, and changes blood flow patterns. Norepinephrine release
        maintains blood pressure.

        b. A releasing hormone from the hypothalamus stimulates ACTH release from the
        pituitary, which stimulates the adrenal cortex to release corticosteroids.
        Glucocorticoids increase blood glucose through the conversion of proteins and
        fats. Mineralocorticoids increase blood volume and pressure by stimulating the
        kidney to reabsorb sodium ions and water.

Suggested Answers to Structure Your Knowledge

   1. Chemical signals that bind to plasma membrane receptors initiate signal-
      transduction pathways that may activate cellular enzymes or affect gene
      expression. Steroid hormones bind with protein receptors inside a cell, and the
      hormone-receptor complex acts as a transcription factor to turn on (or off) specific

   2.    Calcitonin is secreted by the thyroid in response to a rise in Ca2+ levels above a
        set point. Its effects are to stimulate Ca2+ deposit in bones and reduce Ca2+ uptake
        in the intestines and kidneys. As Ca2+ levels in the blood fall, PTH (parathyroid
        hormone) is secreted by the parathyroid glands and reverses the effects of
        calcitonin. PTH also activates vitamin D, which increases Ca2+ uptake from food
        in the intestines.

Answers to Test Your Knowledge

   1. I. melatonin (p.959), f. pineal (p.959)
   2. G. glucocorticoids (p.958), a. adrenal cortex (p.958)
   3. F. glucagon (p.955), d. pancreas (p.955)
   4. B. androgens (p.958), h. testis (p.958)
   5. A. ACTH (p.952), g. pituitary (p.950)
   6. E. epinephrine (p.956), b. adrenal medulla (p.956-8)
   7. L. thyroxine (p.953), j. thyroid (p.953)
   8. D. calcitonin (p.955), j. thyroid (p.953)
   9. C. ADH (p.951), c. hypothalamus (p.950), released from g. pituitary (p.950)
   10. J. oxytocin (p.951), c. hypothalamus (p.950), released from g. pituitary (p.950)

Multiple choice:

   1. e. Steroid hormones often function as neurotransmitters. (p.959)
   2. d. pheromones are signals that function between organisms, whereas hormones
       communicate among the parts within an organism (p.945)
   3. d. TSH-thyroid (p.953)
   4. c. prostaglandins released from placental cells promoting muscle contraction
       during childbirth, with muscle contractions stimulating more prostaglandin
       release (p.948)
   5. d. is secreted by prothoracic glands in insects and triggers molts and development
       of adult characteristics (p.960)
   6. a. prostaglandins (p.948)
   7. c. is released from the posterior pituitary and increases water reabsorption in the
       kidneys (p.951)
   8. b. receives releasing and inhibiting hormones from the hypothalamus through
       portal vessels connecting capillary beds (p.950)
   9. e. an excess of growth hormone (p.952)
   10. e. insulin (p.955)
   11. d. MSH binds to cell surface receptors (p.952)
   12. c. Its release is stimulated by ACTH (p.956)
   13. a. ACTH (p.952)
   14. d. estrogen (p.958)
   15. c. epinephrine (p.956)
   16. d. little thyroxine is produced, TRH and TSH production is not inhibited, and
       thyroid stimulation continues (p.954)
   17. a. whose target tissue is another endocrine gland (p.951)
   18. b. form a hormone-receptor complex inside the cell that regulates gene expression

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