Chapter 7 review questions

Question 1

Level 1:
The study of hormones is called .

Answer 1

endocrinology

Question 2

List the three basic ways hormones act on their target cells.

Answer 2

Alter the rate of enzymatic reactions, control transport of molecules into and out of cells, or change gene expression and protein synthesis in target cells.

Question 3

List five endocrine glands, and name one hormone secreted by each. Give one effect of each hormone you listed.

Answer 3

See Fig. 7.2.

Question 4

Match the following researchers with their experiments:
a. Lower
b. Berthold
c. Guillemin and Schally
d. Brown-Séquard
e. Banting and Best

1. isolated trophic hormones from the hypothalami of pigs and sheep
2. claimed sexual rejuvenation after injections of testicular extracts
3. isolated insulin
4. accurately described the function of the pituitary gland
5. studied comb development in castrated roosters

Answer 4

(a) 4, (b) 5, (c) 1, (d) 2, (e) 3

Question 5

Put the following steps for identifying an endocrine gland in order:
a. Purify the extracts and separate the active substances.
b. Perform replacement therapy with the gland or its extracts and see if the abnormalities disappear.
c. Implant the gland or administer the extract from the gland to a normal animal and see if symptoms characteristic of hormone excess appear.
d. Put the subject into a state of hormone deficiency by removing the suspected gland, and monitor the development of abnormalities.

Answer 5

(d), (b), (c), (a)

Question 6

For a chemical to be defined as a hormone, it must be secreted into the for transport to a(n) and take effect at concentrations.

Answer 6

blood, distant target, very low

Question 7

What is meant by the term half-life in connection with the activity of hormone molecules?

Answer 7

the time required for half a dose of hormone to disappear from the blood

Question 8

Metabolites are inactivated hormone molecules, broken down by enzymes found primarily in the and , to be excreted in the and , respectively.

Answer 8

kidneys and liver, urine and bile

Question 9

Candidate hormones often have the word as part of their name.

Answer 9

factor

Question 10

List and define the three chemical classes of hormones. Name one hormone in each class.

Answer 10

Peptides—three or more amino acids; example: insulin. Steroids—derived from cholesterol; example: estrogen. Amino acid–derived—made from single amino acids; example: thyroid hormone

Question 11

Decide if each of the following characteristics applies best to peptide hormones (P), steroid hormones (S), both classes (B), or neither class (N).
a. are lipophobic and must use a signal transduction system
b. have a short half-life, measured in minutes
c. often have a lag time of 90 minutes before effects are noticeable
d. are water-soluble, and thus easily dissolve in the extracellular fluid for transport
e. most hormones belong to this class
f. are all derived from cholesterol
g. consist of three or more amino acids linked together
h. are released into the blood to travel to a distant target organ
i. are transported in the blood bound to protein carrier molecules
j. are all lipophilic, so diffuse easily across membranes

Answer 11

(a) peptide, (b) peptide, (c) steroid, (d) peptide, (e) peptide, (f) steroid, (g) peptide, (h) all classes, (i) steroid, (j) steroid

Question 12

Why do steroid hormones usually take so much longer to act than peptide hormones?

Answer 12

Steroid hormones usually initiate new protein synthesis, which takes time. Peptides modify existing proteins.

Question 13

When steroid hormones act on a cell nucleus, the hormone-receptor complex acts as a(n) factor, binds to DNA, and activates one or more , which create mRNA to direct the synthesis of new .

Answer 13

transcription factor, genes, proteins

Question 14

Researchers have discovered that some cells have additional steroid hormone receptors on their , enabling a faster response.

Answer 14

cell membrane

Question 15

Melatonin is made from the amino acid _____________, and the catecholamines and thyroid hormones are made from the amino acid ______________.

Answer 15

tryptophan, tyrosine

Question 16

A hormone that controls the secretion of another hormone is known as a(n) hormone.

Answer 16

trophic

Question 17

In reflex control pathways involving trophic hormones and multiple integrating centers, the hormones themselves act as signals, suppressing trophic hormone secretion earlier inthe reflex.

Answer 17

negative feedback

Question 18

What characteristic defines neurohormones?

Answer 18

synthesized by and secreted from neurons

Question 19

List the two hormones secreted by the posterior pituitary gland. Towhat chemical class do they belong?

Answer 19

oxytocin and vasopressin, both peptide neurohormones

Question 20

What is the hypothalamic-hypophyseal portal system? Why is it important?

Answer 20

The portal system is composed of hypothalamic capillaries that take up hormones and deliver them directly to capillaries in the anterior pituitary. The direct connection allows very small amounts of hypothalamic hormone to control the anterior pituitary endocrine cells.

Question 21

List the six hormones of the anterior pituitary gland; give an actionof each. Which ones are trophic hormones?

Answer 21

See Fig. 7.9.

Question 22

Explain long-loop negative feedback.

Answer 22

A hormone from a peripheral endocrine gland decreases pituitary and hypothalamic hormone secretion.

Question 23

When two hormones work together to create a result that is greaterthan additive, that interaction is called . Whenhormone A must both be present to achieve full expressionof hormone B, that interaction is called . When hormone activities oppose each other, that effect is called .

Answer 23

synergism, permissiveness, antagonistic

Question 24

Level 2:
Compare and contrast the terms in each of the following sets:
a. paracrine signal, hormone, cytokine
b. primary and secondary endocrine pathologies
c. hypersecretion and hyposecretion
d. anterior and posterior pituitary

Answer 24

(a) Paracrines—local; cytokines—local or long distance; hormones—long distance. Cytokines—peptides; hormones—peptides, steroids, or amines. Cytokines—made on demand; peptides—made in advance and stored. (b) Primary pathology arises in the last endocrine gland of the pathway. Secondary pathology arises in a gland secreting a trophic hormone. (c) Hypersecretion—too much hormone; hyposecretion—too little hormone. (d) Both secrete peptide hormones. Anterior pituitary gland—true endocrine gland; posterior pituitary—neural tissue.

Question 25

Compare and contrast the three chemical classes of hormones.

Answer 25

See Tbl. 7.1.

Question 26

Level 3:
The terms specificity, receptors, and down-regulation can be applied to many physiological situations. Do their meanings change when applied to the endocrine system? What chemical and physical characteristics do hormones, enzymes, transport proteins, and receptors have in common that makes specificity important?

Answer 26

The meanings do not change significantly. Enzymes, hormone receptors, transport proteins, and receptors are all proteins that bind ligands.

Question 27

Dexamethasone is a drug used to suppress the secretion of adrenocorticotrophic hormone (ACTH) from the anterior pituitary. Two patients with hypersecretion of cortisol are given dexamethasone. Patient A’s cortisol secretion falls to normal as a result, but patient B’s cortisol secretion remains elevated. Draw maps of the reflex pathways for these two patients (see Fig. 7.11b for a template) and use the maps to determine which patient has primary hypercortisolism. Explain your reasoning.

Answer 27

Patient A—cortisol hypersecretion results from ACTH hypersecretion. When dexamethasone suppresses ACTH secretion, the adrenal gland is no longer stimulated. Cortisol secretion decreases as a result. Patient B—problem in the adrenal gland. His normal negative feedback pathways do not operate, and the adrenal gland continues oversecreting cortisol even though ACTH secretion has been suppressed by dexamethasone.

Question 28

Some early experiments for male birth control pills used drugs that suppressed gonadotropin (FSH and LH) release. However, men given these drugs stopped taking them because the drugs decreased testosterone secretion, which decreased the men’s sex drive and caused impotence.
a. Use the information given in Figure 7.9 to draw the GnRH-FSH/LH-testosterone reflex pathway. Use the pathway to show how suppressing gonadotropins decreases sperm production and testosterone secretion.

b. Researchers subsequently suggested that a better treatment would be to give men extra testosterone. Draw another copy of the reflex pathway to show how testosterone could suppress sperm production without the side effect of impotence.

Answer 28

(a) See Fig. 26.8. (b) Both LH and testosterone are needed for gamete formation. Testosterone does not directly suppress gamete formation, but it does have a negative feedback effect and shuts off LH secretion. LH is needed for gamete production, so its absence would suppress gamete synthesis.