Biol 1303 Chapter 9 Notes

A&P CH.9
Major Endocrine glands and their location in the body:
Location: Brain
Hypothalamus
Pineal Gland
Pituitary
Location: Neck, anterior
surface of trachea
Thyroid Gland
Parathyroid Glands
Location: Superior surface of kidneys
Adrenal Glands
Location: Abdominopelvic region
Pancreas
Ovaries (female)
Testes (male)

,What does the endocrine system do?
 This system helps to maintain day-to-day homeostasis through chemicals called
hormones
 This system works with the nervous system, which maintains moment-by-moment
homeostasis

Endocrine vs. Exocrine Glands:
 Endocrine glands
 Glands that secrete a chemical signal directly into the bloodstream
 Endocrine cells can also be found in organs that have primary roles in other
organ systems
 Ex. hypothalamus, pancreas
 Endocrine cells can also be found in tissues
 Ex. adipose tissue
 Exocrine glands
 Secrete chemicals through ducts or tubes
 Ex. salivary glands

General Hormone Action:
 Hormones are released into the bloodstream
 Hormones act on their specific target cells
 The hormone and its target cell interact at the hormone receptor on the target cell
surface
 Hormones are released as a response to a change in the environment, and once the
hormone and target cells interact, homeostasis is restored
 Once homeostasis is restored, hormone secretion stops through a negative feedback
mechanism

Two major types of hormones:
 Steroid hormones
 Dissolve in fats or lipids, therefore can go through target cell membrane
 Made from cholesterol
 Takes longer to act, but generally effects last longer than nonsteroid hormones
 Nonsteroid hormones
 Dissolve in water
 Made from small amino acids, peptides, or large proteins
 Bind to hormone receptor on target cell membrane
 Act faster, but effects are more short-lived than steroid hormones

Steroid hormones go directly into the target cells:
 Steroid hormones pass through the cell membrane of the target cell
 The hormone binds to its receptor inside the cell and stimulates specific genes to make
new proteins
 The new proteins alter the activity of the cell

, How Steroid hormones work:




Examples of steroid hormones:
 Ovaries, testes, adrenals produce androgens (sex hormones) for male or female
characteristics
 Adrenal cortex secrete mineralocorticoids that act on kidneys to increase sodium and
water reabsorption, potassium excretion

Nonsteriod hormones bind to receptors on the target cell membrane:
 Nonsteroids cannot pass through the cell membrane, so they bind to cell surface
receptors on the membrane
 A hormone-receptor complex is formed
 The complex triggers a second messenger to be formed inside the cell
 The second messenger alters the activity of the target cell
 There is an amplified and diversified set of responses

Examples of nonsteriod hormones:
 Cyclic AMP (cAMP)
 Made from ATP