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The
Endocrine
System
I. General Features
• A. Control System
1. Maintains homeostasis
2. Contrast with the nervous system
a. nervous system = fast, shortlived effects
b. endocrine system = slow,
long-lasting effects
General Features (cont.)
B. Glandular System
1. Effects via chemical secretions
2. Contrast with exocrine glands
a. exocrine = ducts, secrete into
body cavities
b. endocrine = ductless, secrete into
bloodstream
General Features (cont.)
• C. Types of Secretions (Hormones)
– 1. Chemistry
• a. Peptide hormones
– i. Water-soluble
– ii. Bind to receptors on cell surface
– iii. Require cAMP within cell to cause effect
 b. Steroid hormones
 i. Lipid-soluble
 ii. Pass directly into target cells to cause
effect
Types of Hormones (cont.)
– 2. Location of effects
• a. Circulating Hormones
– i. Secreted into bloodstream
– ii. Effects occur after entry into blood
– iii. Effects occur distal from secreting gland
• b. Local Hormones (Paracrine)
– i. Eventually enter blood
– ii. Effects occur prior to entry into blood
– iii. Effects occur in close proximity to
secreting gland
II. Anatomy of the Endocrine System
• A. Hypothalamic-Pituitary Axis
– 1. Hypothalamus = neural tissue
• a. Releasing/Inhibitory Hormones control
anterior pituitary
• b. Direct neural stimulation via
hypothalamohypophyseal tract controls
posterior pituitary
Hypothalamic-Pituitary Axis (cont.)
2. Pituitary (“master” gland)
a. Anterior Pituitary - true gland
i. Human Growth Hormone (hGH)
-increased growth/metabolism
-via production of insulin-like growth
factors (IGF’s)
ii. Thyroid Stimulating Hormone (TSH)
-stimulates hormone secretion (primarily
thyroxine) from thyroid gland
Anterior Pituitary (cont.)
iii. Follicle Stimulating Hormone (FSH)
males - initiates increased sperm
production
females - stimulates egg maturation
iv. Leutinizing Hormone (LH)
males - maintains increased sperm production
females - stimulates ovulation
v. Prolactin
stimulates milk production in mammary glands
Anterior Pituitary (cont.)
• vi. Adrenocorticotropic Hormone
(ACTH)
- stimulates hormone secretion
from adrenal cortex
–Primarily of cortisol
b. Posterior Pituitary
• i. Not a true gland, but extension of
hypothalamus
• ii. Hormones made in hypothalamus
and stored in posterior pituitary
• iii. Hormones:
– Oxytocin - stimulates:
• Milk release from mammary glands
• Uterine contractions during childbirth
Posterior Pituitary (cont.)
• Anti-Diuretic Hormone (ADH; also
known as vasopressin)
– Stimulates increased water reabsorption
(primarily from urine back into blood)
– Released when dehydrated or low blood
pressure
Endocrine Anatomy (cont.)
• B. Thyroid and Parathyroid Glands
– 1. Thyroid - controlled by TSH
• a. Thyroxine (T3/T4)
– i. increases metabolic rate
• b. Calcitonin – regulation of electrolytes
– i. stimulates storage of Ca+2 and PO4-2 in
bones and teeth
– 2. Parathyroid
• a. Parathryroid Hormone (PTH)
– i. stimulates release of Ca+2 and PO4-2 from
bones and teeth
Endocrine Anatomy (cont.)
• C. Adrenal Glands
– 1. Adrenal Cortex - controlled by ACTH
• a. Aldosterone
– i. Regulation of electrolyte concentrations
» via control of release/retention in urine
• b. Cortisol (glucocorticoids)
– i. Long-term coping with stress
• c. Androgens
– i. secondary sexual traits in both sexes and sex drive
(females)
Adrenal Glands (cont.)
• 2. Adrenal Medulla - controlled by
sympathetic nervous system
– a. Epinephrine/Norepinephrine
• i. short-lived, immediate response to stress
• ii. Both secretions collectively referred to as
“adrenalin”
Endocrine Anatomy (cont.)
• D. Pancreas
– 1. Islet cells
• a. Insulin (Beta cells)
– i. promotes storage of nutrients in body
tissues
• b. Glucagon (Alpha cells)
– i. promotes release of nutrients from body
tissues