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Chapter 10 Lecture Outline
page 1
Chapter 10 Endocrine System
function: controls and coordinates activity of other organs; maintains
homeostasis
hormone = chemical messenger carried to target cells by blood
endocrine gland = cell or tissue that secretes hormones
target cell = cell that has receptors for a given hormone
A. chemical classification
1. amino acid derivatives: epinephrine, norepinephrine, thyroid
hormones
2. peptides: all hormones secreted by hypothalamus, pituitary gland,
heart, kidneys, thymus, digestive tract and pancreas
BIOL 2404
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Chapter 10 Lecture Outline
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3. steroids: all hormones secreted by the adrenal cortex and gonads
(ovaries and testes)
B. how hormones work
hormone + receptor → change in cell activity
1. receptor is part of cell membrane (peptide hormones, epinephrine
and norepinephrine)
 hormone binds to receptor
 enzyme in cell membrane makes second messenger inside cell
 second messenger causes change in target cell activity
a. activates or inhibits intracellular enzymes
b. opens or closes membrane channels
c. adds new components to cell membrane (receptors, carriers,
channels)
2. receptor is located in the cytosol or nucleus (steroid hormones and
thyroid hormone)
 hormone binds to receptor
 hormone and receptor bind to DNA (chromosomes) and activate one
or more genes
 activated gene causes the formation (transcription and translation) of
new proteins which could be enzymes or structural proteins
 the proteins cause a change in target cell activity
C. relationship between hypothalamus and pituitary
1. anterior pituitary gland
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derived from epithelial tissue, not nerve tissue
located inferior to hypothalamus
receives hormonal signals from hypothalamus
communication between hypothalamus and anterior pituitary occurs
through hypophyseal portal system
capillaries in hypothalamus
BIOL 2404
pick up hypothalamic
hormones
Strong/Fall 2006
Chapter 10 Lecture Outline
page 3
portal vessels
capillaries in anterior pituitary
drop off hypothalamic
hormones
2. posterior pituitary - not really a gland
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extension of the brain tissue
attached to hypothalamus by infundibulum
contains axon terminals from two hypothalamic nuclei
hormones secreted by neurons in these nuclei are released and
diffuse into capillaries in the posterior pituitary
D. hypothalamus
1. location – median inferior brain
2. basic structure – individual nuclei
3. hormones and their functions
a. regulatory hormones
control (increase or decrease) the secretion of anterior pituitary
hormones
b. antidiuretic hormone (ADH)
 secreted in response to increased blood osmotic pressure
 acts on kidneys to conserve water (decreases urine output)
 released in posterior pituitary gland
c. oxytocin
 secreted in response to uterine contractions, acts on uterine
muscle cells to increase contraction strength
 secreted in response to suckling, acts on contractile cells in
mammary glands to expel milk
 stimulates smooth muscle contraction in ductus deferens
and prostate gland (emission is the accumulation of
semen before ejaculation)
 released in posterior pituitary gland
BIOL 2404
Strong/Fall 2006
Chapter 10 Lecture Outline
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E. anterior pituitary gland
1. location – inferior to hypothalamus; in sella turcica (sphenoid)
2. basic structure – clumps of endocrine cells
3. hormones and their functions
a. thyroid stimulating hormone (TSH) – released in response to
TRH from hypothalamus; stimulates thyroid gland to release
more thyroid hormone
b. adrenocorticotropic hormone (ACTH) - released in response to
CRH from hypothalamus; stimulates adrenal cortex to
release more glucocorticoids
c. gonadotropins: follicle stimulating hormone (FSH) and
luteinizing hormone (LH) – released in response to GnRH
from hypothalamus; stimulate gonads to produce gametes
and hormones
d. prolactin (PRL) – controlled by hypothalamic hormones;
stimulates milk secretion by mammary gland
e. growth hormone (GH) - controlled by hypothalamic hormones;
stimulates growth, especially in skeletal muscle and
cartilage; causes release of stored nutrients into blood
F. thyroid gland
1. location – anterior to trachea, inferior to larynx
2. basic structure –
a. gross: two lobes, isthmus
b. microscopic: follicles are spheres of epithelium filled with
colloid
3. hormones and their functions
a. thyroid hormone = T3 (triiodothyronine) + T4
(tetraiodothyronine or thyroxine)
BIOL 2404
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Chapter 10 Lecture Outline
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produced in colloid inside follicles
follicle cells provide raw materials and control TH release
TH acts directly on mitochondria to increase ATP production
TH causes synthesis of enzymes needed for increased
cellular metabolism
 indirect effects: increased oxygen consumption, increased
heat production
b. calcitonin
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secreted by C cells in response to high blood calcium level
acts on bone to inhibit osteoclasts
acts on kidneys to increase calcium excretion
lowers blood calcium level
4. disorders
a. hypothyroidism
b. hyperthyroidism
(goiter is not a disorder, it is a symptom
a goiter indicates that the thyroid gland cannot make adequate
amounts of thyroid hormone)
5. control of secretion
BIOL 2404
TRH
hypothalamus
TSH
anterior pituitary gland
TH
thyroid gland
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Chapter 10 Lecture Outline
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G. parathyroid glands (4)
1. location – embedded in posterior thyroid gland
2. basic structure – chief cells
3. hormones and their functions
parathyroid hormone (PTH)
 secreted in response to low blood calcium level
 stimulates osteoclasts; inhibits osteoblasts
 acts on kidneys to decrease calcium excretion
 acts on kidneys to secrete calcitriol (vitamin D)
 calcitriol increases intestinal absorption of calcium
 overall effect is to increase blood calcium level
H. adrenal glands (2)
1. location – superior to kidneys
2. basic structure –
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cortex - outer layer produces corticosteroids; 3 zones
outer zone secretes mineralocorticoids (aldosterone)
middle zone secretes glucocorticoids (cortisol)
inner zone secretes gonadocorticoids (androgens and estrogens)
b. medulla - modified sympathetic ganglion; chromaffin cells secrete
epinephrine and norepinephrine
3. hormones and their functions
a. aldosterone
 secreted in response to low blood sodium level, high blood
potassium level, low blood pressure, or low blood volume
 acts on kidneys to conserve sodium and excrete potassium
 indirectly maintains body water content
BIOL 2404
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Chapter 10 Lecture Outline
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b.
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cortisol
secreted in response to ACTH
stimulates release of glucose from the liver
stimulates synthesis of glucose in the liver from amino acids
and fatty acids
 stimulates the removal of amino acids from muscle tissue and
lipids from adipose tissue
 overall effect is to increase blood glucose level
 at abnormally high levels or when used as a drug, has antiinflammatory effects and suppresses immune system
c. androgens
 no major physiological effects at normal levels
d. epinephrine and norepinephrine
 secreted in response to signals from sympathetic preganglionic
fibers
 has same effects as sympathetic nervous system
I. pancreas
1. location of pancreas – inferior and posterior to stomach
2. basic structure –
a. exocrine tissue = pancreatic acini are primary component of
pancreas; secrete digestive enzymes
b. endocine tissue = pancreatic islets scattered throughout;
 alpha cells secrete glucagon
 beta cells secrete insulin
3. hormones and their functions
a. insulin
 secreted in response to high blood glucose level
BIOL 2404
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Chapter 10 Lecture Outline
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 acts on target cells by inserting glucose transport proteins
into cell membranes
 causes liver and muscle cells to store glucose
 overall effect is to decrease blood glucose level
 causes most cells to turn amino acids into proteins
 causes adipose cells to store triglycerides as fat
 tissues that are not insulin targets: liver, kidney cells, CNS
b. glucagon
 secreted in response to low blood glucose level and high
blood amino acid level
 acts on liver and muscle to release glucose into blood
 acts on liver to make glucose from amino acids and fatty
acids
 overall effect is to increase blood glucose level
4. diabetes mellitus
a. type I caused by inability to secrete insulin
b. type II caused by inability of target cells to respond normally to
insulin (low number of insulin receptors)
 both types characterized by high blood glucose level
 normal blood glucose is 100 mg/dL (fasting) and somewhat
higher following a meal (140 to 160 mg/dL)
 above 300 mg/dL glucose is excreted in the urine, causing
excess urine output
 because cells can’t get enough glucose, they have to use
other fuels
 fat is the main alternative fuel and it’s use can lead to a
condition called ketoacidosis
BIOL 2404
Strong/Fall 2006