Endocrine System: Biochemistry, Secretion, and Transport of Hormones

Interactive Physiology Worksheet:

Endocrine System: Biochemistry, Secretion, and Transport of Hormones

1. Place the following hormones into one of the three categories of hormones (peptides, amines, or

steroids): T4 (thyroxine), estradiol, norepinephrine, insulin, aldosterone, glucagon, cortisol, growth

hormone, T3 (triiodothyronine), epinephrine, testosterone, and vasopressin (ADH).

Peptides Amines Steroids

2. Peptide hormones are synthesized as large precursor hormones called __________________.

The hormones (or prohormones) are stored in _________________ __________________ and

released from the cell by _______________________. Do peptide hormones require a carrier in the

bloodstream? _____________________________________________________

3. Catecholamines are produced in the ____________________ of the adrenal gland and are –

classified as _________________ hormones because they are derived from __________________.

Stimulation of the chromaffin cells causes an influx of ____________________ ions, which causes the

vesicles to merge with the plasma membrane and release the hormone by ____________________.

Are catecholamines water soluble or lipid soluble? ________________________________________.

4. Thyroid hormones include two molecules called __________________ and _________________.

T3 consists of two _______________ molecules plus _____ iodine molecules and is _______________

abundant than T4. Are carriers required for the transport of thyroid hormones?


5. All steroid hormones are derived from _____________________; which steroid hormone is

produced is determined by the _________________ present in the cell. The common precursor

molecule for all steroid hormones is ______________________. Steroid hormones enter the

Page 1 of 2 BIO1014 Anatomy and Physiology II Lab

© 2013 South University

bloodstream by _______________ and ________________ require a carrier. The rate of secretion of

steroid hormones is ______________________ than that of catecholamines because steroid

hormones are not ______________________.

6. Preganglionic sympathetic fibers trigger the release of ___________________ and

____________________ (hormones) from the ________________ ________________ (gland). This is

an example of neural regulation of hormone secretion.

7. Two examples of hormonal regulation of hormone secretion include: (1) the negative feedback

of T3 and T4 to decrease ________________ levels; and (2) the negative feedback of cortisol, which

decreases both _________________ and ________________________ levels.

8. Besides increased levels of plasma glucose and amino acids (humoral regulation), increased

levels of ____________________ (hormone) and stimulation of the __________________ nervous

system also increase plasma insulin levels.

9. Some hormones are released in rhythmic 24-hour patterns known as ______________________

rhythms. _________________________ is a hormone allowing stressful stimuli to override this

pattern and increase the plasma hormone levels. In contrast, _________________ hormones (amine

hormones) are an example of large amounts of the hormones being bound to carrier proteins in the

plasma, forming a large circulating reservoir. Thus, acute changes do not produce large changes in

the plasma levels of these hormones.

10. The _____________________ and ______________________ are the major organs that

metabolize hormones. The type of hormone determines how fast they are metabolized.

__________________ and _______________________ are rapidly metabolized, while

__________________ and _____________________ take longer to metabolize.

Page 2 of 2 BIO1014 Anatomy and Physiology II Lab

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