The Endocrine System – Questions
and Answers
Why is cyclic AMP considered a "second messenger"? - ANSWER-it activates
inactive enzymes in the cell to give the response attributed to the hormone
What factors determine the responsiveness of a target cell to a hormone? -
ANSWER-hormone concentration, abundance of target cell's hormone receptors,
influence exerted by other hormones
What are the three influences over hormone secretion? - ANSWER-signals from the
nervous system, chemical changes in the blood, other hormones
What is the functional importance of the hypophyseal portal veins? - ANSWER-they
are the direct route taken by hypothalamic hormones to act immediately on anterior
pituitary cells, before the hormones are diluted or destroyed in the general circulation
Which anterior pituitary hormones stimulate a second endocrine gland to release a
hormone? - ANSWER-FSH, LH, TSH, ACTH
You have noticed your neighbor's 8-year-old child is the same height as her 5-year-
old cousin. This child could be deficient in which hormone? - ANSWER-hGH
If a person has a pituitary tumor that secretes a large amount of hGH and the tumor
cells are not responsive to regulation by GHRH and GHIH, will hyperglycemia or
hypoglycemia be more likely? Explain your answer. - ANSWER-Hypoglycemia
Explain how blood levels of T3/T4, TSH, and TRH would change in a laboratory
animal that has undergone a thyroidectomy (complete removal of its thyroid gland). -
ANSWER-low blood levels of T3 and T4 would stimulate increase in levels of TRH,
which would stimulate increased levels of TSH; however, removal of the thyroid
gland would prevent production of T3 and T4
Where are the hormones secreted by the posterior pituitary produced? How do OT
and ADH get from their production site to the capillaries of the posterior pituitary? -
ANSWER-(a) hypothalamic neurosecretory cells;
(b) they are packed into vesicles and transported down the axons to the axon
terminals in the posterior pituitary until exocytosis is triggered, then the hormones
are released and diffuse into the capillaries of the posterior pituitary
Functionally, how are the axons of hypothalamic neurosecretory cells and the
hypophyseal portal veins similar? - ANSWER-both are direct routes for hormone
release that do not involve the general circulation
Is OT regulated by positive or negative feedback? What feedback stimuli influence
the release of OT? - ANSWER-(a) positive feedback;
, (b) stretching of the cervix and suckling
Sometimes during difficult deliveries or following long labor a synthetic form of
oxytocin is given to the mother. Why? - ANSWER-to increase OT production and
uterine contractions for childbirth
What effect would drinking a large volume of water have on the osmotic pressure of
your blood? The level of ADH? - ANSWER-(a) lower osmotic pressure;
(b) decrease level of ADH
Which cells of the thyroid gland secrete T3 and T4? Which secrete calcitonin? Which
of these hormones are also called thyroid hormones? - ANSWER-(a) follicular cells;
(b) parafollicular cells;
(c) T3 and T4
How are the thyroid hormones synthesized, stored, and transported in the
bloodstream? - ANSWER-synthesis: iodide is brought into the follicles, is oxidated,
binds to the tyrosine component of thyroglobulin to ultimately form T3 and T4
(triiodothyronine and tetraiodothyronine or thyroxin); storage: in the follicle; blood
transport: carried bound to transport proteins in the blood, mainly TGB
How is the secretion of T3 and T4 regulated?
24. - ANSWER-via TRH and low blood levels of T3 and T4, as well as other factors
such as cold environment, hypoglycemia, high altitude, and pregnancy
Why might hypothyroidism (low thyroid hormone levels) in an infant result in mental
retardation? - ANSWER-thyroid hormone stimulates body growth, particularly the
growth and development of nervous tissue
What is the primary target tissue for calcitonin? What is the action of calcitonin? -
ANSWER-(a) osteoclasts;
(b) inhibit bone breakdown or resorption
What are the primary target tissues for PTH and calcitriol? - ANSWER-PTH:
osteoclasts, kidney tubules, GI tract; calcitriol: GI tract
How is secretion of parathyroid hormone regulated?
How is secretion of parathyroid hormone regulated?
How is secretion of parathyroid hormone regulated? - ANSWER-by blood levels of
calcium ions
In which ways are the actions of PTH and calcitriol similar and different? - ANSWER-
similarity: both increase blood calcium ion levels: differences: PTH increases number
and activity of osteoclasts, slows the rate of calcium ion loss from blood into urine,
and stimulates the kidneys to produce calcitriol, whereas calcitriol acts on the GI
tract to increase the rate of calcium ion absorption from food into the blood
What is the benefit of adding vitamin D to various food products such as milk?
and Answers
Why is cyclic AMP considered a "second messenger"? - ANSWER-it activates
inactive enzymes in the cell to give the response attributed to the hormone
What factors determine the responsiveness of a target cell to a hormone? -
ANSWER-hormone concentration, abundance of target cell's hormone receptors,
influence exerted by other hormones
What are the three influences over hormone secretion? - ANSWER-signals from the
nervous system, chemical changes in the blood, other hormones
What is the functional importance of the hypophyseal portal veins? - ANSWER-they
are the direct route taken by hypothalamic hormones to act immediately on anterior
pituitary cells, before the hormones are diluted or destroyed in the general circulation
Which anterior pituitary hormones stimulate a second endocrine gland to release a
hormone? - ANSWER-FSH, LH, TSH, ACTH
You have noticed your neighbor's 8-year-old child is the same height as her 5-year-
old cousin. This child could be deficient in which hormone? - ANSWER-hGH
If a person has a pituitary tumor that secretes a large amount of hGH and the tumor
cells are not responsive to regulation by GHRH and GHIH, will hyperglycemia or
hypoglycemia be more likely? Explain your answer. - ANSWER-Hypoglycemia
Explain how blood levels of T3/T4, TSH, and TRH would change in a laboratory
animal that has undergone a thyroidectomy (complete removal of its thyroid gland). -
ANSWER-low blood levels of T3 and T4 would stimulate increase in levels of TRH,
which would stimulate increased levels of TSH; however, removal of the thyroid
gland would prevent production of T3 and T4
Where are the hormones secreted by the posterior pituitary produced? How do OT
and ADH get from their production site to the capillaries of the posterior pituitary? -
ANSWER-(a) hypothalamic neurosecretory cells;
(b) they are packed into vesicles and transported down the axons to the axon
terminals in the posterior pituitary until exocytosis is triggered, then the hormones
are released and diffuse into the capillaries of the posterior pituitary
Functionally, how are the axons of hypothalamic neurosecretory cells and the
hypophyseal portal veins similar? - ANSWER-both are direct routes for hormone
release that do not involve the general circulation
Is OT regulated by positive or negative feedback? What feedback stimuli influence
the release of OT? - ANSWER-(a) positive feedback;
, (b) stretching of the cervix and suckling
Sometimes during difficult deliveries or following long labor a synthetic form of
oxytocin is given to the mother. Why? - ANSWER-to increase OT production and
uterine contractions for childbirth
What effect would drinking a large volume of water have on the osmotic pressure of
your blood? The level of ADH? - ANSWER-(a) lower osmotic pressure;
(b) decrease level of ADH
Which cells of the thyroid gland secrete T3 and T4? Which secrete calcitonin? Which
of these hormones are also called thyroid hormones? - ANSWER-(a) follicular cells;
(b) parafollicular cells;
(c) T3 and T4
How are the thyroid hormones synthesized, stored, and transported in the
bloodstream? - ANSWER-synthesis: iodide is brought into the follicles, is oxidated,
binds to the tyrosine component of thyroglobulin to ultimately form T3 and T4
(triiodothyronine and tetraiodothyronine or thyroxin); storage: in the follicle; blood
transport: carried bound to transport proteins in the blood, mainly TGB
How is the secretion of T3 and T4 regulated?
24. - ANSWER-via TRH and low blood levels of T3 and T4, as well as other factors
such as cold environment, hypoglycemia, high altitude, and pregnancy
Why might hypothyroidism (low thyroid hormone levels) in an infant result in mental
retardation? - ANSWER-thyroid hormone stimulates body growth, particularly the
growth and development of nervous tissue
What is the primary target tissue for calcitonin? What is the action of calcitonin? -
ANSWER-(a) osteoclasts;
(b) inhibit bone breakdown or resorption
What are the primary target tissues for PTH and calcitriol? - ANSWER-PTH:
osteoclasts, kidney tubules, GI tract; calcitriol: GI tract
How is secretion of parathyroid hormone regulated?
How is secretion of parathyroid hormone regulated?
How is secretion of parathyroid hormone regulated? - ANSWER-by blood levels of
calcium ions
In which ways are the actions of PTH and calcitriol similar and different? - ANSWER-
similarity: both increase blood calcium ion levels: differences: PTH increases number
and activity of osteoclasts, slows the rate of calcium ion loss from blood into urine,
and stimulates the kidneys to produce calcitriol, whereas calcitriol acts on the GI
tract to increase the rate of calcium ion absorption from food into the blood
What is the benefit of adding vitamin D to various food products such as milk?
