1191 Endocrine Exam

Front 1

1. Compare and contrast the roles of the nervous and endocrine systems in homeostasis.

Back 1

A. Together the nervous and endocrine systems coordinate functions of all body systems.
1. The nervous system controls body actions through nerve impulses and neurotransmitters.
2. The endocrine system controls body activities by releasing mediator molecules called hormones.
B. The nervous and endocrine systems act as a coordinated interlocking supersystem, the neuroendocrine system.
1. Parts of the nervous system stimulate or inhibit the release of hormones.
2. Hormones may promote or inhibit the generation of nerve impulses.
C. The nervous system causes muscles to contract or glands to secrete. The endocrine system affects virtually all body tissues by altering metabolism, regulating growth and development, and influencing reproductive processes.
D. Table 18.1 compares the characteristics of the nervous and endocrine systems.

Front 2

2. Distinguish between an endocrine gland and an exocrine gland.

Back 2

A. The body contains two kinds of glands: exocrine and endocrine.
1. Exocrine glands secrete their products into ducts, and the ducts carry the secretions to the target site.
2. Endocrine glands secrete their products (hormones) into the interstitial fluid surrounding the secretory cells from which they diffuse into capillaries to be carried away by blood.
B. Endocrine glands constitute the endocrine system and include the pituitary, thyroid, parathyroid, adrenal, pancreas, kidneys, gastrointestinal organs, and pineal glands (Figure 18.1).

Front 3

3. Describe how hormones interact with receptor cells

Back 3

A. Hormones have powerful effects when present in very low concentrations.
B. The Role of Hormone Receptors
1. Although hormones travel in blood throughout the body, they affect only specific target cells.
2. Target cells have specific protein or glycoprotein receptors to which hormones bind.
3. Receptors are constantly being synthesized and broken down.
a. When a hormone is present in excess, down-regulation, the decrease in the number of receptors, may occur.
b. When a hormone is deficient, up-regulation, an increase in the number of receptors, may occur.

Front 4

4. Discuss how hormone receptors can be blocked

Back 4

4. Synthetic hormones that block the receptors for particular naturally occurring hormones are available as drugs. (Clinical Connection)

Front 5

5. Distinguish between circulating and local hormones.

Back 5

1. Hormones that travel in blood and act on distant target cells are called circulating hormones or endocrines.
2. Hormones that act locally without first entering the blood stream are called local hormones.
a. Those that act on neighboring cells are called paracrines.
b. Those that act on the same cell that secreted them are termed autocrines.
3. Figure 18.2 compares the site of action of circulating and local hormones.

Front 6

6. List the hormones that are lipid soluble.

Back 6

aldosterone, cortisol, androgens, testosterone, calcitriol, estrogen, progesterone, T3, T4, NO

Front 7

7. List the hormones that are water soluble.

Back 7

Epinephrine, norepinephrine, melatonin, histamine, serotonin, oxytocin, ADH, hGH, TSH, ATCH, FSH, LH, PRL, MSH, insulin, glucagon

Front 8

8. Describe how lipid and water soluble hormones are transported in blood.

Back 8

1. Most water-soluble hormones circulate in plasma in a free, unattached form.
2. Most lipid-soluble hormones bind to transport proteins to be carried in blood.
3. The transport proteins improve the transportability of lipid-soluble hormones by making them temporarily water-soluble, retard passage of the small hormone molecules through the kidney filter thus slowing the rate of hormone loss in urine, and provide a ready reserve of hormone already present in blood.

Front 9

9. Explain why some hormones may be taken orally while others must be taken by injection.

Back 9

4. Protein and peptide hormones, such as insulin, will be destroyed by digestive enzymes and, therefore, must be given by injection (Clinical Connection).

Front 10

10. Describe the mechanism of action of lipid-soluble hormones.

Back 10

1. Lipid-soluble hormones bind to and activate receptors within cells.
2. The activated receptors then alter gene expression which results in the formation of new proteins.
3. The new proteins alter the cells activity and result in the physiological responses of those hormones.
4. Figure 18.3 shows this mechanism of action.

Front 11

12. Describe the mechanism of action of water-soluble hormones.

Back 11

1. Water-soluble hormones alter cell functions by activating plasma membrane receptors,.
a. The water-soluble hormone (first messenger) binds to the cell membrane receptor, which set off a cascade of events inside the cell (Figure 18.4).
b. A second messenger is released inside the cell where hormone stimulated response takes place.
2. A typical mechanism of action of a water-soluble hormone using cyclic AMP as the second messenger is seen in Figure 18.4.
a. The hormone binds to the membrane receptor.
b. The activated receptor activates a membrane G-protein which turns on adenylate cyclase.
c. Adenylate cyclase converts ATP into cyclic AMP which activates protein kinases.
d. Protein kinases phosphorylate enzymes which catalyze reactions that produce the physiological response.
3. Since hormones that bond to plasma membrane receptors initiate a cascade of events, they can induce their effects at very low concentrations.

Front 12

13. Describe the permissive, synergistic, and antagonistic effects of hormones.

Back 12

1. Permissive effects - first hormone enhances the effect of a later hormone action
1. ex. estrogen up-regulates progesterone receptors in uterus
2. ex. TH increases effect of epinephrine on breakdown of triglycerides in adipocytes

3. Synergistic effects - two hormones acting together have a greater effect than the sum of the effects of each hormone acting independently
1. ex. both FSH and estrogen necessary for normal oocyte development
2. ex. FSH and testosterone together produce more sperm than alone
4. Antagonistic effects - one hormone opposes the action of the other hormone, net effect
1. ex. insulin and glucagon