Chapter 9, The Endocrine System, Part A

The Endocrine System
Chapter 9
1. Overview
a. Second control system
b. Uses chemical messengers (hormones); released into the blood; usually long term control
c. Hormones control several major processes
i. Reproduction
ii. Growth and development
iii. Mobilization of body defenses
iv. Maintenance of much of homeostasis
v. Regulation of metabolism
2. Hormones
a. Overview
i. Hormones produced by specialized cells
ii. Cells secrete secrete hormones into extracellular fluids
iii. Blood transfers hormones to target sites
iv. These hormones have specific effects on these cells
b. Chemistry – hormones classified as:
i. Amino acid/protein based
ii. Steroids—made from cholesterol
iii. Prostaglandins—made from highly active lipids
c. Mechanism of hormone action
i. Hormones affect only certain tissues or organs (target cells, tissues, or organs)
1. Target cells must have specific protein receptors
ii. Hormone binding alters cellular activity:
1. Direct gene activity
2. Indirectly by a second messenger system
iii. Direct gene action (steroid hormone action)
1. Diffuse through the plasma membrane of target cells
2. Enter the nucleus
3. Bind to a specific protein within the nucleus and to specific sites on the cell’s DNA
4. Activate genes that result in synthesis of new proteins
iv. Indirect: Second messenger system; 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
2. Stops when
3. Release triggered by
a. Levels of
b. Levels of
c. Nerve impulses
3. Overview of the system
a. Spread throughout the body
b. Sometimes part of other systems
c. List of major organs
i. Pituitary gland
ii. Thyroid gland
iii. Parathyroid glands
iv. Adrenal glands
v. Pineal gland
vi. Thymus gland
vii. Pancreas
viii. Gonads (ovaries and testes)
4. Pituitary gland
a. Size of a pea
b. Hangs from a stalk from the hypothalamus in the brain
c. Protected by the sphenoid bone
d. Two functional lobes
i. Anterior pituitary – glandular tissue
ii. Posterior pituitary – nervous tissue
e. Referred to as “master endocrine gland”
f. Anterior pituitary hormones (6)
i. Targets are non-endocrine (two affect non-endocrine targets)
1. GH = Growth Hormone
2. PRL = Prolactin
ii. Tropic hormones: affect other endocrine glands (four stimulate other endocrine glands)
1. TSH = Thyroid-stimulating hormone (thyrotropic hormone)
2. ACTH = Adrenocorticotropic hormones
3. Gonadotropins
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; fats to be broken down for a source of energy
v. Disorders
1. Pituitary dwarfism
a. Results from hyposecretion of growth hormone during childhood
2. Gigantism
a. Results from hypersecretion of growth hormone during childhood
3. Acromegaly
a. Results from hypersecretion of growth hormone during adulthood
b. Prolactin
i. In women stimulates and maintains milk production following childbirth
ii. In men function in males is unknown
c. Adrenocorticotropic hormone
i. Regulates endocrine activity of the adrenal cortex
d. Thyroid-stimulating hormone
i. Influences growth and activity of the thyroid gland
e. Gonadotropins: regulate hormonal activity of the gonads
i. Follicle-stimulating hormone (FSH)
1. In ovaries stimulates follicle development
2. In testes stimulates sperm development
ii. Luteinizing hormone (LH)
1. In females triggers ovulation of an egg
2. In males stimulates testosterone production
6. Pituitary/hypothalamus relationship
a. Regulated by releasing and inhibiting hormones produced by the hypothalamus
b. Hypothalamus 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 reabsorbtion by the kidneys
2. In large amounts, causes vasoconstriction leading to increased blood pressure
3. AKA vasopressin
iii. Transported to posterior pituitary via