Anatomy & Physiology 34B
Chapter 16 - Endocrine System
I.
Overview
A. Introduction to the Endocrine System
B. Hypothalamus and Pituitary Gland
C. Thyroid and Parathyroid Glands
D. Pancreas
E. Adrenal Glands
F. Gonads & Other Endocrine Glands
G. Hormones and their actions
H. Eicosanoids and Paracrine Signaling
I. Endocrine Pathologies
II. Introduction to the Endocrine System
A. The nervous & _____________ systems coordinate functions of all body systems.
B. The nervous system controls homeostasis rapidly via ________ ____________
conducted along axons of neurons; causes muscles to contract and glands to secrete
hormones; has brief effects.
C. Endocrine system glands release messenger molecules, called ______________, into the
bloodstream more slowly for delivery to target cells; longer lasting effects.
D. The nervous system can stimulate or inhibit ___________ release, and hormones can
promote or inhibit __________ impulses.
E. ______________ of endocrine gland hormones include:
1. Regulate the internal environment by adjusting _______/volume ratios (e.g.,
aldosterone)
2. Regulate metabolism & _____ balance (e.g., thyroid hormones)
3. Regulate cardiac and smooth __________ contraction (e.g., epinephrine and
norepinephrine)
4. Regulate other _____________ secretions (e.g., hypothalamus & pituitary hormones)
5. Maintain _______________ despite disruptions (e.g., pancreatic hormones)
6. Regulate the _____________ system (e.g., cytokines)
7. Assist in ________ and development (e.g., growth hormones)
8. Assist in _______________ (hormones that influence oogenesis, spermatogenesis,
conception, delivery)
F. Cells _________________ with each other in 4 ways
1. _______ junctions - protein pores that allow nutrients, electrolytes, or signaling
molecules to move from cell to cell
2. _________transmitters - released by neurons, diffuse across a synaptic cleft, and bind
to receptors on an adjacent cell
3. ____________ and _____________ (local hormones) are released by a cell into
surroundings, and affect the same cell or those nearby.
2
4. _____________ – chemical messengers secreted by endocrine glands into the blood
stream to travel to _________ cells with specific receptors
III. Gland Types
A. Exocrine Glands - secrete their products into ________; include:
1. Sudoriferous (e.g.: ________, mammary glands)
2. Sebaceous (____ glands)
3. ____________
4. ____________ (products include pancreatic digestive enzymes)
B. Endocrine Glands - products (___________) are secreted into the extracellular space,
then diffuse into _______stream
1. Entirely endocrine glands include the _____________, thyroid, parathyroid, adrenal,
and pineal glands.
2. Partially endocrine glands include the _________________, thymus, pancreas,
ovaries, testes, kidneys, stomach, liver, small intestines, skin, heart, and placenta.
IV. Endocrine Glands & their Hormones
A. ___________________ – the true master gland; secretes:
1. Posterior pituitary hormones – oxytocin and vasopressin (____), made in the
hypothalamus are sent to the _________ pituitary, then released when needed
2. ____________ & inhibiting neurohormones - GHRH, GHIH (somatostatin), TRH,
GnRH, PRH, PIH, and CRH, which stimulate the _________ pituitary to release
specific hormones.
3. Releasing & inhibiting neurohormones travel through the hypophyseal __________
system to the anterior pituitary
B. _____________ Gland – sits in the sella turcica; connected to the hypothlamus via the
infundibulum; divided into two major regions
1. Posterior pituitary (_______hypophysis) - contains axon terminals of neurons
(__________) whose cell bodies are in the supraoptic and paraventricular nuclei of
the hypothalamus. Hypothalamus neurons send hormones to posterior pituitary
a. _____________ (OT) - stimulates uterine contractions & milk ejection
b. Vasopressin (_____) - stimulates ________ reabsorption from kidneys into
blood to prevent dehydration (deficiency produces diabetes insipidus)
2. Anterior pituitary (_______hypophysis) - hormone release is stimulated by
releasing hormones and inhibited by inhibiting hormones from the
_______________.
3. _______________ (feeder) anterior pituitary hormones that stimulate other
endocrine glands to release their hormones include:
a. Thyroid Stimulating Hormone (____) - stimulates the _________ to synthesize
and release T3 & T4 hormones.
b. Follicle-Stimulating Hormone (_____) - stimulates ova development and
estrogen production in __________ & sperm production in the ___________
3
c.
4.
Luteinizing Hormone (____ or ICSH in males) - stimulates ovulation and
progesterone & estrogen secretion in _______, and testosterone secretion in the
__________
d. Adrenocorticotropic Hormone (______) - influences production and secretion
of hormones by the adrenal ______
e. Human Growth Hormone (____ or somatotropin) – stimulates the liver to
produce IGFs and ________ in body tissues, esp. muscle, cartilage, bones, and
fat. Actions include:
1) ___________ synthesis – DNA transcription and mRNA translation are
stimulated; protein catabolism supressed
2) __________ metabolism – adipocytes are stimulated to catabolize fat and
release free fatty acids and glycerol into the bloodstream to provide energy for
growing tissues
3) Carbohydrate metabolism – stimulates ___________ synthesis and storage
4) _______________ balance – promotes Na+, K+, and Cl- retention by the
kidneys and Ca2+ absorption by the intestines for delivery to growing tissues
5) Hyposecretion of GH in children causes ____________
6) Hypersecretion in children causes ______________, in adults it causes
__________ in which bones continue growth
___________________ anterior pituitary hormones affect other organs
a. Prolactin (_____) - initiates and maintains milk production (lactation) by mammary
glands in the ___________
b. Melanocyte stimulating hormone (_____) stimulates skin _________cytes to
produce more pigment
C. _______ Gland - located on lateral sides of the trachea; secretes thyroid hormone and
calcitonin
1. Thyroid hormone (___) - ___ (triiodothyronine) & ___ (thyroxin) from follicular
cells.
2. Thyroid follicles are filled with colloid containing a protein precursor to TH called
thyroglobulin, and enzymes
3. THs are made from the amino acid tyrosine and iodine
a. Iodine (I-) from food is actively transported into follicular cells
b. Enzymes attach I- to tyrosine on the thyroglobulin molecule in the colloid to make
T3 and T4 (thyroxine)
c. Thyroglobulin is endocytosed into follicular cells, where enzymes free T3 and T4
from the protein
d. T3 and T4 are lipid-soluble, thus diffuse out of the cells into the plasma and bind to
thyroid-binding proteins
e. T3 and T4 bind to nuclear receptors and initiate protein synthesis
f. T4 is converted by enzymes to T3, the active hormone, in target tissues
4. Thyroid hormones increase basal metabolic rate (BMR) by increasing ATP
production, and maintaining body temperature
a. Hypothyroidism in children causes ___________ (mental retardation), in
adults it causes _____________ (low metabolism, weight gain, hypertension)
or endemic ___________ (thyroid gland hypertrophy)
4
b.
Hyperthyroidism in adults causes ___________ disease - high metabolic
rate, weight loss, insomnia, bulging eyes
5. _____________ - from parafollicular (C) cells decreases serum ______________
& phosphate levels, and promotes calcium deposition in bones by stimulating
osteo______
D. _______________ Glands - on posterior sides of thyroid glands; secrete parathyroid
hormone (____), whose functions include:
1. Increases osteo______ activity, raising serum calcium levels
2. Initiates __________ formation (a vitamin D derivative) from the kidneys, which
increases Ca2+ uptake from the GI tract, raising serum Ca2+ levels.
3. Hyposecretion causes a rapid decline in blood calcium levels, and leads to fatal
__________ in 3-4 days
4. Hypersecretion causes _______ to become soft, deformed and fragile
E. _____________ - located posterior & inferior to stomach; has both exocrine &
endocrine functions:
1. Exocrine - ________ cells secrete digestive enzymes
2. Endocrine cells include pancreatic __________ cells:
a. Alpha () cells secrete __________, which raises blood glucose levels by
stimulating the liver to hydrolyze glycogen
b. Beta () cells secrete ________, which lowers blood glucose levels by the
following:
1) Promotes movement of ________ through cell membranes
2) Stimulates liver to convert glucose to ___________
3) Assists in synthesis of proteins & ______
3. Diabetes __________ is a failure to produce insulin (type I diabetes) or reduced
sensitivity of insulin receptors on target cells (type II diabetes)
a. Type __ diabetes (IDDM) usually begins in childhood due to the destruction of
__ cells by autoantibodies; insulin must be injected to control the symptoms
b. Type ___ diabetes (NIDDM) usually occurs in middle aged adults, but increasing
in overweight children; insulin is still secreted, but target cells are insulin
_________; can often be controlled by _____ and exercise
c. Uncontrolled diabetes mellitus is the leading cause of adult __________, renal
failure, gangrene, and limb amputations
F. ___________ (suprarenal) glands - found on superior kidneys; consist of an outer cortex
and an inner medulla.
1. Adrenal ________ consists of 3 zones that secrete ________:
a. Zona ________________ (superficial area) - secretes mineralocorticoids
(____________), which promote Na+ retention and K+ excretion by the kidneys
b. Zona __________ (middlelayer) - secretes glucocorticoids (__________),
which help to maintain blood glucose levels, resist stress, and are antiinflammatory.
5
5.
1) Hyposecretion of mineral- and glucocorticoids results in _____________
disease - _____glycemia, hypotension, electrolyte imbalance, dehydration,
weight loss, skin bronzing, weakness
2) Hypersecretion of corticosteroids results in __________ syndrome _______glycemia, hypertension, weakness, and edema; can also be caused by
prescription steroids, such as prednisone
c. Zona __________ (innerlayer) - secretes ______corticoids (androgens, estrogen,
& progesterone)
Adrenal ________ - secretes epinephrine & norepinephrine, which produce
effects similar to ____________ NS (fight or flight)
VI. Gonads & Other Endocrine Glands
A. _______ are the sex organs of males (____) and females (______), which produce both
hormones and gametes (sperm & eggs)
1. _______ - located in the pelvic cavity; hormones are produced in
a. Ovaries produce ___________, as well as inhibin & relaxin
1) Inhibin supresses _____ secretion by the anterior pituitary
2) __________ relaxes ligaments in preparation for childbirth
b. ______ _______ - scar tissue formed from an ovarian follicle also secretes
estrogen and ____________, which regulate the menstrual cycle, sustain
pregnancy, and prepare the mammary glands for lactation
2. Testes - contain seminiferous tubules, in which sperm form, and ___________ cells
that produce male sex hormones, primarily ______________, which stimulates
development of the male reproductive system
B. Endocrine Functions of other organs include
1. ___________ - produces human chorionic gonadotropin (___), estrogen &
progesterone
2. Pineal Gland - on third ventricle of brain; secretes __________ believed to regulate
diurnal rhythms.
3. __________ Gland - bilobed organ at base of trachea; secretes thymosin, which
promotes the proliferation and maturation of ___ lymphocytes
4. ___________ & Small Intestine - secrete:
a. __________ - promotes gastric juice secretion
b. Gastric Inhibitory Peptide (___) - stimulates insulin release
c. Secretin & Cholecystokinin (___) - stimulate release of pancreatic digestive
enzymes & bile.
5. Skin – epidermal keratinocytes produce vit. __, the first step in the synthesis of calcitriol,
which is completed by the liver & kidneys
6. Kidneys – secrete _______, which signals the adrenals to release aldosterone; also
erythropoietin, which stimulates _____ production, and helps to synthesize calcitriol,
active vitamin D.
7. Liver - produces insulin-like growth factors (___ I & II), which mediates the action of
human ____ hormone, and angiotensinogen, which increases blood pressure
6
8. Heart - ______ produce atrial natriuretic peptide (____), which causes the excretion
of sodium and water, decreasing blood volume and blood pressure.
V. Hormones & their Actions
A. The basic classes of ________ (peptides, monoamines, & steroids) are derived either
from _______ acids or cholesterol
1. _________ comprise most of the body’s hormones, and include:
a. ____________ from the thyroid gland
b. Most hormones from the pituitary gland, ___________, & parathyroid glands
c. Peptides are synthesized like any protein: a gene is transcribed to _____, then
translated as tRNAs bring the precise sequence of _______ acids coded for by the
mRNA
d. Most peptides begin as nonactive _______hormones in the ER, then are cleaved
to a ____hormone, which is processed and packaged in the Golgi complex to form
the active _____ hormone (e.g. proinsulin cleaved to insulin and C-peptide)
e. These hormones must be ___________ because they are hydrolyzed during
digestion
2. Amine hormones are derived from two _______ acids and always have an amine
group (-NH2).
a. _______________ is converted to melatonin in the pineal gland
b. ______________ is used to form thyroxin in the thyroid gland, as well as
catecholamines in the adrenal medulla
c. ________________ and norepinephrine (catecholamines) bind to surface plasma
membrane receptors like other peptide hormones
d. _______________ acts like a steroid, diffusing through the cell membrane and
binding to nuclear receptors.
3. Steroidal hormones are lipids synthesized from ___________ Common steroids
include:
a. ___________ and cortisone, produced by the adrenal cortex
b. Sex hormones: estrogen, progesterone, & testosterone, produced by the
__________ (ovaries & testes)
c. Because steroids are hydrophobic, they must bind to hydrophilic transport proteins
(___________ and globulins) to travel in the bloodstream
d. Steroids can be taken __________ or injected
B. _____________ of Hormone Secretion
1. Hormone levels are maintained by a ________ feedback system and autonomic
_________ impulses, and humoral (blood borne) substances
a. ___________ feedback is similar to a thermostat:
1) When a hormone level is low, the endocrine gland is signaled to increase
production to the __________ cells
2) Once a sufficient amount has been secreted, the target cells signal the
endocrine gland to _________ production
7
b.
__________ impulses via the ANS cause some endocrine glands, such as the
adrenal _________, to secrete hormones. Other glands affected are the
1) _______________, in which neurosecretory cells secrete neurohormones that
influence specific cells in the ___________ gland (hypophysis)
2) This causes the pituitary cells to secrete specific hormones to other _____
organs, which may secrete other hormones
3) As the hormones increase in the blood stream, they feed back and
____________ hypothalamus secretion
c. ___________ substances, such as calcium and glucose can trigger hormone release
1) Low blood calcium stimulates release of PTH from the ________________
glands; high blood calcium causes calcitonin secretion from the ___________
2) High blood glucose levels stimulates the pancreas to release ____________,
whereas low blood glucose levels cause the pancreas to secrete ____________
C. Hormone Receptors & Mode of Action
1. Hormone _________ are specific for one hormone, and act like switches to turn
metabolic pathways on or off when the hormone binds to them
2. Hormone receptors are found in plasma ____________, on mitochondria, and other
organelles, and in the _________ of target cells
a. ___________ pass through the plasma membrane, bind to nuclear receptors, and
can stimulate _________ synthesis to alter the metabolism of the target cell
b. Thyroxin (___) hormone binds to receptors in the nucleus and ribosomes, to
stimulate protein synthesis, as well as _______, to stimulate aerobic respiration
c. __________ & catecholamines bind to surface plasma membrane receptors and
activate 2nd _________, such as cAMP, cGMP, diacylglycerol, and inositol
triphosphate, in the cytosol
D. Enzyme ______________ refers to the fact that one hormone can activate thousands of
enzyme molecules in a ____________ effect; therefore target cells do not need many
hormone receptors
E. Hormones are cleared from the blood by metabolism in the ______ and __________, and
excreted in the bile and urine
F. __________ (adjustment) of target cell sensitivity is accomplished by up-regulation and
down regulation of hormone receptors
1. ___-regulation is an increase in a cell’s number of hormone receptors, which
__________ the cell’s sensitivity to the hormone (e.g., oxytocin receptors increase in
the uterus before childbirth)
2. ______-regulation is a decrease in a cell’s number of hormone receptors, often in
response to _____ hormone concentrations (e.g., high insulin concentrations cause a
down-regulation of insulin receptors in type ___ diabetes)
G. Hormones can have three types of ___________ effects – synergistic, permissive, or
antagonistic
1. _________ effects, in which two or more hormones act _______ to produce a greater
effect than the sum of their individual effects. Example:
a. _____________ from the pancreas might elevate blood glucose levels 10 mg/dl
b. ________________ from the adrenal medulla might elevate BG levels 5 mg/dl
c. Both glucagon and epinephrine can elevate BG levels _____ mg/dl
8
2. ___________ effects, in which one hormone enhances the target organ’s response to a
_________ hormone secreted later. Example: cortisol
a. _________ is required for glucagon and the catecholamines to have their full effects
b. The effects of cortisol are mainly ____________, and include:
1) Promotes ______________________ in the liver
2) Causes the breakdown of skeletal muscle ______________
3) Enhances ________________
4) Suppresses the ______________ system
5) Causes negative ______________ balance – decreases blood Ca2+ levels by
decreasing Ca2+ absorption and increasing excretion
6) Influences ___________ function – excess or deficiency cause mood changes
and alteration in memory and learning
3. ___________ effects, in which one hormone _________ the action of another (e.g.,
insulin lowers blood glucose level, glucagon __________ it)
VI. Stress & Adaptation
A. ________ is any situation that upsets homeostasis and threatens one’s physical or
emotional well-being
B. The stress response or general ___________ syndrome is the body’s reaction to stress,
which has three stages
1. ________ reaction, characterized by elevated levels of norepinephrine,
____________, aldosterone, and angiotensin, resulting in glycogenolysis, fluid and
electrolyte retention, and elevated blood pressure
2. Stage of ____________ occurs after glycogen is exhausted, and is characterized by
elevated levels of ACTH and __________, and the breakdown of fat and protein for
fuel
3. Stage of _____________ sets in if fat reserves are depleted; characterized by
increasing protein breakdown, weakening of the body, and often ________
VII. Eicosanoids & Paracrine Signaling
A. _________ are hormone like messengers that travel short distances and stimulate nearby
cells
B. Many paracrines are _________, which have 20-carbon backbones, and are derived from
______________ acid, a cell membrane phospholipid. Eicosanoids include
1. _____________ mediate allergic and inflammatory reactions
2. _____________ is produced by blood vessel walls, where it inhibits blood clotting and
vasoconstriction
3. Thromboxanes are produced by blood ___________. During injuries, the override
prostacyclin to stimulate vasoconstriction and clotting
4. Prostaglandins (___) are produced in most body organs, and have diverse effects
a. The ____ family relaxes smooth muscle in the bladder, intestines, bronchioles, and
uterus, but stimulates contraction of the smooth muscle of blood vessels
b. ____ has the opposite effects
C. Anti-______________ drugs include steroidal and nonsteroidal forms
1. Steroidal anti-inflammatory drugs (_____s), such as ___________, inhibit
inflammation by blocking the release of _____________ acid from the plasma
membrane, thus inhibiting all eicosanoids
9
2. Nonsteroidal anti-inflammatory drugs (________s), such as _______ and ibuprofen,
block cycloxygenase (______), an enzyme needed for prostaglandin synthesis
VIII. Endocrine Pathologies
A. __________________of endocrine pathologies depends on the complexity of the reflex
1. If a pathology (deficiency or excess) arises in the ________ endocrine gland in a reflex,
it is called a ____________ pathology (e.g., if a damaged adrenal gland produces
excess cortisol, it’s called primary hypersecretion)
2. If dysfunction occurs in a tissue producing __________ hormones, the problem is a
_____________ pathology (e.g., if CRH and/or ACTH secretion diminishes, it’s called
secondary hyposecretion)
3. The diagnosis of endocrine pathologies depends on understanding negative __________
in the control pathways