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End of Chapter Answers

Reviewing the Concepts Answers

  1. Given that hormones contact virtually all cells in the body, why are only certain cells affected by a particular hormone?  Cells that are affected by a particular hormone are called target cells. Target cells have receptors for the hormone that is released. Other cells do not have the receptor and cannot be affected by the hormone.
  2. How do lipid-soluble (steroid) and water-soluble hormones differ in their mechanisms of action?  
    1. Lipid-soluble hormones can move through the lipid bi-layer into a cell where the receptors reside. A hormone receptor complex moves to the DNA to activate genes.
    2. Water-soluble hormones are composed of amino acids and cannot pass through the lipid bi-layer. They attach to receptors on the surface of the cell (first messenger). The second messenger molecule inside of the cell is activated to influence enzymes within the cell.
  3. Compare negative and positive feedback mechanisms with regard to regulation of hormone secretion. Provide an example of each.  
    1. A negative feedback system – the pancreas secretes the hormone insulin when blood glucose is high to stimulate glucose storage. When the blood glucose becomes low, the pancreas stops secreting insulin. 
    2. A positive feedback system – during childbirth the pituitary secretes the hormone oxytocin to stimulate uterine contractions which in turn stimulate the production of more oxytocin which increases the frequency and intensity of uterine contractions.
  4. How do the anterior and posterior lobes of the pituitary gland differ in size and relationship with the hypothalamus?  The anterior pituitary is larger than the posterior pituitary and is directly connected to the hypothalamus by a blood portal system. The much smaller posterior pituitary is connected to the hypothalamus by neurosecretory cells.
  5. List the hormones secreted by the anterior lobe of the pituitary and their functions.  
    1. Growth hormone – growth of bones and muscles
    2. Thyroid stimulating hormone – stimulates thyroid gland to produce hormones
    3. Adrenocorticotropic hormone  – stimulates the adrenal cortex
    4. Prolactin – stimulates the mammary glands to produce milk
    5. Follicle-stimulating hormone and luteinizing hormone stimulate the ovaries and testes
  6. List the hormones released by the posterior lobe of the pituitary and their functions.  
    1. Anti-diuretic hormone – affects the kidney tubules
    2. Oxytocin – affects the uterus and the mammary glands
  7. What are the effects of thyroid hormone?  Thyroid hormone affects most cells of the body and increases metabolism and head production.
  8. Describe the feedback system by which calcitonin and parathyroid hormone regulate levels of calcium in the blood.  Proper levels of calcium must be maintained in the blood. The thyroid produces calcitonin in response to high levels of calcium in the blood. This promotes calcium storage. When levels become too low, the parathyroid releases parathyroid hormone which increases calcium levels in the blood by stimulating bone destroying cells (osteoclasts), removal of calcium from urine, and absorption by blood.
  9. What are the major functions of the glucocorticoids, mineralocorticoids, and gonadocorticoids secreted by the adrenal cortex?
    1. Glucocorticoids – affect glucose homeostasis
    2. Mineralocorticoids – affect mineral homeostasis and water balance
    3. Gonadocorticoids – sex hormones in males and females
  10. What is the fight-or-flight response? Which hormones are critical in initiating this response?  Hormones released by the adrenal medulla, epinephrine and norepinephrine, are responsible for the fight or flight response when faced with stress or danger. The response includes increases in heart rate, respiratory rate and blood glucose, as well as vasoconstriction and dilation.
  11. What hormones are secreted by the pancreas? What are their functions?
    1. Glucagon stimulates the liver to convert glycogen to glucose, and form glucose from lactic acid and amino acids.
    2. Insulin increases transport of glucose into cells, inhibits breakdown of glycogen to glucose, prevents conversion of amino acids to glucose.
  12. Explain the differences between type 1 and type 2 diabetes mellitus.
    1. Type 1 – the immune system attacks cells of the pancreas and stops or inhibits insulin production (usually begins at a young age).
    2. Type 2 – a decrease of insulin receptors on cells causes insulin to be ineffective (usually seen in adults).
  13. What is the basic function of hormones secreted by the thymus gland?  The hormones of the thymus are involved in the maturation of the white blood cells known as T-lymphocytes.
  14. What roles might melatonin play in the body?  Affects daily rhythms (sleep), seasonal depression, inhibits fertility hormones, and aging.
  15. How do local signaling molecules differ from true hormones?  Local signaling molecules are lipid molecules of various kinds that are released by most cells and have local effects. They are not considered true hormones because they do not affect distant tissues.
  16. a
  17. d
  18. c
  19. c
  20. a
  21. Lipid-soluble; water-soluble
  22. giantism; acromegaly
  23. calcitonin; parathormone
  24. adrenal cortex
  25. insulin; glucagon

Hints for Applying the Concepts Questions

  1. Hint: Cortisone is a glucocorticoid.  What affects do those have at increased levels?
  2. Hint: Matt’s age can be used to make an educated guess about his type of diabetes.
  3. Hint: Theresa’s symptoms and the timing of their onset suggest melatonin may be involved.
  4. Hint:  Other than the ovaries and testes, what other endocrine gland has the ability to produce sex hormones?

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