Chapter 13 - Endocrine System

Question 1

Protein hormones act initially on target cells by
(A) attaching to receptors on the nuclear membrane.
(B) attaching to receptors in the nucleolus.
(C) diffusing through the plasma membrane.
(D) attaching to receptors on the plasma
membrane.
(E) attaching to receptors on the rough endoplasmic reticulum membrane.

Answer 1

D. Protein hormones initiate their action by binding externally to transmembrane receptor proteins in the target-cell plasma membrane. Receptors for some hormones (e.g., TSH, serotonin, epinephrine) are linked to G proteins; other receptors, including those for insulin and growth hormone, have protein kinase activity (see Chapter 13 II A).

Question 2

Which of the following statements concerning adrenal parenchymal cells is true?
(A) Those of the zona fasciculata produce androgens.
(B) Those of the adrenal medulla produce epinephrine and norepinephrine.
(C) Those of the zona glomerulosa produce glucocorticoids.
(D) Those of the cortex contain numerous secretory granules.
(E) Those of the zona reticularis produce mineralocorticoids.

Answer 2

B. Chromaffin cells in the adrenal medulla synthesize and store epinephrine and norepinephrine in secretory granules, which also contain ATP, chromogranins, and enkepha­lins. The cortical parenchymal cells of the zona fasciculata produce glucocorticoids, and those of the zona glomerulosa produce mineralocorticoids. The cortical parenchymal cells do not store their secretory products and thus do not contain secretory granules (see Chapter 13 VI).

Question 3

Characteristics of pinealocytes include which one of the following?
(A) They produce melatonin.
(B) They resemble astrocytes.
(C) They contain calcified concretions of
unknown function.
(D) They act as postganglionic sympathetic cells.
(E) They are unaffected by dark and light cycles.

Answer 3

A. Pinealocytes, the parenchymal cells of the pineal gland, produce melatonin at night and serotonin during the day. The pineal gland also contains neuroglial cells that resemble astro­cytes, and its interstitium has calcified concretions called brain sand (see Chapter 13 VII).

Question 4

Prolactin is synthesized and secreted by which of the following cells?
(A) Acidophils in the pars distalis
(B) Basophils in the pars tuberalis
(C) Somatotrophs in the pars distalis
(D) Basophils in the pars intermedia
(E) Gonadotrophs in the pars distalis

Answer 4

A. Prolactin is produced by mammotrophs, one of the two types of acidophils located in the pars distalis of the pituitary gland. As their name implies, these cells produce a hormone that regulates the development of the mammary gland during pregnancy and lactation (see Chapter 13 III A).

Question 5

ACTH is produced by which of the following cells?
(A) Chromophobes in the pars distalis
(B) Neurosecretory cells in the median
eminence
(C) Basophils in the pars distalis
(D) Neurons ofthe paraventricular nucleus
in the hypothalamus
(E) Basophils in the pars intermedia

Answer 5

C. ACTH is produced by corticotrophs, a type of basophil, present in the pars distalis of the pituitary gland (see Chapter 13 III A) .

Question 6

The histological appearance of a thyroid gland being stimulated by TSH would show which of the following?
(A) Decreased numbers of follicular cells
(B) Increased numbers of parafollicular cells
(C) Column-shaped follicular cells
(D) An abundance of colloid in the lumen of
the follicle
(E) Decreased numbers of parafollicular capillaries

Answer 6

C. Stimulation of the thyroid gland by TSH causes the follicular cells to become more active and column shaped. They form apical pseudopods and engulf colloid, which is removed from the lumen of the follicle by endocytosis and broken down by controlled lysosomal hydrolysis to yield the thyroid hormones T3 and T4. Parafollicular cells and capillaries do not contain receptors for TSH (see Chapter 13 IV).

Question 7

A 40-year-old woman is diagnosed with Graves disease. Which of the following characteristics would be associated with her condition?
(A) Inadequate levels of iodine in her diet
(B) Weight gain
(C) Flattened thyroid follicular cells
(D) Excessive production of thyroid hormones
(E) Increased amounts of follicular colloid

Answer 7

D. Graves disease (exophthalmic goiter) results in an enlarged thyroid gland due to stimulation of the follicular cells to produce an excessive amount of thyroid hormones by binding of auto­ immune antibodies to TSH receptors. Follicular cells actively remove colloid from the lumen
of the follicles. Heat intolerance and weight loss are common, but the disease is not caused by iodine deficiency (see Chapter 13 IV B Clinical Considerations).

Question 8

Which one of the following hormones lowers blood calcium levels by inhibiting bone resorption?
(A) Calcitonin
(B) Epinephrine
(C) Parathyroid hormone
(D) Prolactin
(E) T3

Answer 8

A. Calcitonin lowers blood calcium levels and thus has an effect antagonistic to that of parathyroid hormone. It is produced by parafollicular cells of the thyroid gland (see Chapter 13 IV D).

Question 9

A 51-year-old man underwent surgery
for removal of a carcinoma on his trachea. After surgery, he suffered excessive nervous­ ness, muscle cramps, and spasmodic skeletal muscle contractions in his arms, legs, and feet. Laboratory tests revealed markedly low levels of calcium in his blood. Treatment with intravenous calcium and vitamin D led to recovery in a few weeks. Which one of the following conditions is responsible for these symptoms in this patient following surgery?
(A) Hypothyroidism
(B) Hyperthyroidism
(C) Hypoparathyroidism
(D) Graves disease
(E) Hyperparathyroidism

Answer 9

C. Upon removal ofthe carcinoma from his neck, the parathyroid glands were also removed or damaged, causing hypoparathyroidism (a lack ofparathyroid hormone that increases blood calcium). Treatment with calcium (and vitamin D, which aids in its absorption) corrected these symptoms. The marked neuromuscular irritability in the absence of calcium reveals its importance in regulating skeletal muscle contraction.

Question 10

Which one of the following hormones plays a role in regulating body temperature by promoting heat production?
(A) Calcitonin
(B) Epinephrine
(C) Parathyroid hormone
(D) Prolactin
(E) Triiodothyronine (T3)

Answer 10

E. T3 and T4 both increase the basal metabolic rate, which affects heat production and body temperature. These thyroid hormones also have many other effects (see Chapter 13 IV D).