CH. 20 Endocrine System

Question 1

How are the communication methods between the nervous system and endocrine system differ?

Answer 1

nervous system uses nerve impulses along axons to release the neurotransmitter into the synaptic cleft right at the target cells

the endocrine system uses hormones as chemical messengers; transported through the body to target cells by circulatory system

Question 2

Explain the relation between the release of hormones, target cells, and target organs.

Answer 2

The endocrine glands release hormones (hōr′mōn; hormao =
to rouse) into the blood (figure 20.2). Hormones are chemical
messengers that change the metabolic activity of the target cells.
Only cells with specific receptors for the hormone (enabling the
hormone to bind to the cell) respond to that hormone. These cells
are called target cells, and the organs that contain them are called
target organs. In contrast, organs, tissues, or cells that do not have
the specific receptor for a hormone do not bind or attach the hormone
and do not respond to it.

Question 3

What are the 3 distinct groups in which hormones can be classified chemically?

Answer 3

■ Protein (prō′tēn) hormones are formed from chains of amino
acids. Most of our body’s hormones are protein hormones.
Smaller chains are called peptide hormones. An example is
growth hormone.
■ Biogenic amines (bī′ō-jen-ik ă-mēn′, am′in) are small
molecules produced by altering the structure of a specific
amino acid. An example is thyroid hormone.
■ Steroid (ster′oyd) hormones are a type of lipid derived from
cholesterol. An example is testosterone.

Question 4

What are the two ways in which hormone levels are regulated?

Answer 4

• Negative feedback: when a stimulus starts a process, and eventually either the hormone that is secreted or a product of its effects causes the process to slow down or turn off.
• Postitive feedback: accelerates the original process, either to ensure that the pathway continues to run or to speed up its activites

Question 5

What are the 3 ways in which the hypothalamus regulates endocrine activity as the master control center?

Answer 5

1) special cells in hypothalamus secrete specific hormones (regulatory hormones) that influence the secretory activity of the anterior pituitary gland
- Releasing hormones (stimulate production and secretion of specific anterior pituitary hormones) or inhibiting hormones (deter the production and secretion of specific anterior pituitary hormones)
2) hypothalamus produces two hormones that are transported and stored in the posterior pituitary
- antidiuretic hormone and oxytocin
3) oversees the stimulation and hormone secretion of the adrenal medulla

Question 6

In what three distinct areas is the anterior pituitary separated into?

Answer 6

1) pars distalis
2) pars intermedia
3) pars tuberalis

Question 7

What are the seven major hormones secreted by the anterior pituitary?

Answer 7

6/7 are tropic hormones, or hormones that stimulate other endocrine glands or cells to secrete other hormones

1) thyroid stimulatin hormone (TSH)
2) prolactin (PRL)
3) follicle stimulating hormone (FSH)
4) luteinizing hormone (LH)
5) melanocyte stimulating hormone (MSH)
6) growth hormone (GH)
7) adrenocorticotropic hormone (ACTH)

Question 8

What are the two hormones stored in the posterior pituitary?

Answer 8

1) antidiuretic hormone: stimulates reabsorption of water from tubular fluid in kidneys; stimulates vasoconstriction in arterioles of body, thereby raising blood pressure
2) oxytocin: in females, stimulates smooth muscle contraction in uterine wall; stimulates milk ejection from mammary glands

in males, stimulates contraction of smooth muscle of male reproductive tract

Question 9

Explain the process of the regulation of thyroid hormone secretion.

Answer 9

1. A stimulus (such as low body temperature or a decreased level
   of thyroid hormone in the blood) starts the feedback process.
   This stimulus signals the hypothalamus and causes it to release
   thyrotropin-releasing hormone (TRH).
2. TRH travels through the hypothalamo-hypophyseal portal
   system to stimulate thyrotropic cells in the anterior pituitary,
   causing them to synthesize and release thyroid-stimulating
   hormone (TSH).
3. Increased levels of TSH stimulate the follicular cells of the
   thyroid gland to release thyroid hormone (TH) into the blood.
4. TH stimulates its target cells (many of the cells in the body),
   increasing cellular metabolism. Basal body temperature rises as
   a result of this stimulation.
5. The increased heat produced as a product due to increased
   metabolism elevates body temperature and inhibits the release
   of TRH by the hypothalamus. Also, TH reduces the response of
   anterior pituitary cells to TRH, thus inhibiting the interactions
   of the hypothalamus and anterior pituitary. As TH levels rise in
   the blood, the anterior pituitary stops secreting TSH, and so the
   thyroid gland is no longer stimulated to release TH.

Question 10

What are the three separate regions of the adrenal cortex?

Answer 10

1) zona glomerulosa
2) zona fasciculata
3) zona reticularis

Question 11

What hormones do alpha and beta cells secrete, respectively?

Answer 11

alpha cells secrete glucagon and beta cells secrete insulin