Chapter 9 part a

The Endocrine System

Chapter 9

1.     Overview

a.    Second control system

b.    Chemical messengers- uses chemical messengers(hormones); released into the blood: usually long term control

c.    Hormones control several major processes- reproduction, growth and development, mobilization of body defenses, maintenance of much of homeostasis, regulation of metabolism.

2.    Hormones

a.    Overview

                                          i.    Hormones produced by specialized cells.

                                        ii.    Cells secrete hormones into extracellular fluids.

                                       iii.    Blood transfers hormones to target sites.

                                       iv.    Specific effects- these hormones have specific effects on these cells.

b.    Chemistry – hormones classified as: amino acid/ protein based, steroids-made from cholesterol, prostaglandins- made from highly active lipids.

c.    Mechanism of action

                                          i.    Target cells, tissues, or organs- hormones affect only certain tissues or organs. Target cells must have specific protein receptors

                                        ii.    Hormone binding alters cellular activity

                                       iii.    Direct gene action

1.     Diffuse through the plasma membrane of target cells

2.    Enter the nucleus

3.    Bind to a specific protein within the nucleus, bind to specific sites on cell’s DNA

4.    Activate genes that result in synthesis of new proteins

                                       iv.    Second messenger system(indirect); the hormone:

1.     Binds to a membrane receptor

2.    Does not enter the cell

3.    Sets off a series of reactions that activates an enzyme

4.    Catalyzes a reaction that produces a second-messenger molecule

5.    Oversees additional intracellular changes to promote a specific response

                                         v.    How hormone release is controlled

1.     Levels in the blood are mostly maintained by negative feedback

2.    Stops when an appropriate level in the blood is reached

a.    Release triggered by  

b.    Levels of other hormones

c.    Levels of certain ions in the blood

d.    Nerve impulses usually sympathetic nervous system

3.    Overview of the system

a.    Spread throughout the body

b.    Sometimes part of other systems

c.    List of major organs

4.    Pituitary gland= master gland

a.    Size- pea

b.    Hangs from the hypothalamus in the brain

c.    Protected by the sphenoid bone

d.    Two functional lobes- anterior pituitary- glandular tissue, posterior pituitary- nervous tissue.

e.    Referred to as- the master gland

f.    Anterior pituitary hormones- 6 pituitary hormones

                                          i.    Targets are non-endocrine- 2 non-endocrine targets

1.     GH = growth hormone

2.    PRL = prolactin

                                        ii.    Tropic hormones: affect other endocrine glands- 4 tropic hormones

1.     TSH = thyroid stimulating hormone (thyrotropic hormone)

2.    ACTH = adrenocorticotropic hormone

3.    Gonadotropins-2

a.    FSH =

b.    LH =

5.    Hormones of the anterior pituitary

a.    Growth hormone

                                          i.    General metabolic hormone

                                        ii.    Major effects are directed to growth of skeletal muscles and long bones

                                       iii.    Plays a role in determining final body size

                                       iv.    Causes amino acids to be built into proteins, and causes fats to be broken down for source of energy

                                         v.    Disorders

1.     Pituitary dwarfism results from hyposecretion of GH during childhood

2.    Gigantism results from hypersecretion of GH during childhood

3.    Acromegaly results from hypersecretion of GH during adulthood

b.    Prolactin

                                          i.    In women it stimulates and maintains milk production following childbirth

                                        ii.    In men function is unknown

c.    Adrenocorticotropic hormone(ACTH)

                                          i.    Regulates endocrine activity of the adrenal cortex

d.    Thyroid-stimulating hormone(TSH)

                                          i.    Influences growth and activity of the thyroid gland

e.    Gonadotropins regulate hormonal activity of the glands

                                          i.    Follicle-stimulating hormone(FSH)

1.     In ovaries stimulates follicle(egg)  development in ovaries

2.    In testes stimulates sperm development in testes

                                        ii.    Luteinizing hormone(LH)

1.     In females triggers ovulation of an egg in females

2.    In males stimulates testosterone production in males

6.    Pituitary/hypothalamus relationship-hormonal release is regulated by releasing and inhibiting hormones produced by the hypothalamus

a.    Hypothalamus hormones produces two hormones transported to the posterior pituitary

                                          i.    Oxytosin

1.     Stimulates contractions of the uterus during labor, sexual relations, and breastfeeding

2.    Causes milk ejection in a nursing woman

                                        ii.    Antidiuretic hormone(ADH)

1.     Inhibits urine production by promoting water reabsorption by the kidneys

2.    Causes vasoconstriction leading to increased blood pressure

3.    AKA vasopressin

                                       iii.    Transported to posterior pituitary via