Download I. General Characteristics of the Endocrine System

CHAPTER 13: ENDOCRINE SYSTEM
OBJECTIVES:
1.
Explain why the endocrine system is so closely related to the nervous system.
2.
Distinguish between an endocrine gland and an exocrine gland.
3.
Define the term hormone and explain its general characteristics.
4.
Distinguish between a steroidal and non-steroidal hormone, in terms of composition and
action.
5.
Locate the following endocrine glands (organs) on a diagram: hypothalamus, pituitary,
pineal gland, thyroid, parathyroid, thymus, adrenals, pancreas, ovaries, and testes.
6.
Name the three endocrine glands (see above) that are actually divided into two endocrine
glands with different functions.
7.
For each of the glands listed in #5 & #6 above, name the hormone(s) they secrete,
identify the target organ of each hormone, and the effect of each hormone.
8.
Name the "master" of the anterior pituitary gland.
9.
Define the term gonadotropin, name the two gonadotropins secreted by the anterior
pituitary gland, and distinguish between them according to their actions.
10.
Explain how the posterior pituitary gland does not produce hormones, but does secrete
them.
11.
Name the gland that requires iodine to produce most of its hormones.
12.
Describe how calcium levels are maintained in the blood.
13.
Name the two hormones that work together to regulate water and electrolyte levels in the
blood and therefore regulate blood pressure.
14.
Describe how glucose levels are maintained in the blood.
15.
Explain why the thymus gland decreases in size as we age.
16.
Name the gland (hormone) whose production is stimulated by sunlight.
17.
Define the term gonad, list the primary gonads in both sexes, and name the hormones that
target those gonads.
18.
Explain what is meant by "secondary sexual characteristics", name the hormone that
causes their development in both sexes, and list target organs.
19.
Name the hormones secreted by the ovary, distinguish which particular portion of the
ovary secretes each, and name target organs and actions of those hormones.
20.
Distinguish between dwarfism, giantism, and acromegaly.
21.
Explain why so few cases of cretinism are seen today.
22.
Compare and contrast cretinism, myxedema, Grave's Disease, and goiter.
23.
Distinguish between Addison's Disease and Cushing's Syndrome.
24.
Compare and contrast the two types of the disease Diabetes Mellitus.
25.
Describe seasonal affective disorder (SAD) in terms of cause, symptoms, and treatment.
I.
GENERAL CHARACTERISTICS OF THE ENDOCRINE SYSTEM
The general function of the endocrine system is to integrate body systems (i.e. maintain
homeostasis), in conjunction with the nervous system. Recall that glands are effectors
or responsive body parts that are stimulated by motor impulses from the autonomic
nervous system. Some of these glands, endocrine glands compose the endocrine system.
See Figure 13.1, page 468.
II.
A.
ENDOCRINE GLAND = a gland that secretes hormones directly into the
bloodstream; a ductless gland.
B.
Exocrine gland = a gland that secretes substances into ducts which then leave the
body (i.e. sweat/sebaceous glands) or into a internal space or lumen (i.e. digestive
glands). Exocrine glands are not part of the endocrine system!
C.
HORMONE = a very powerful substance secreted by an endocrine gland into the
bloodstream, that affects the function of another cell or "target cell".
D.
See Fig 13.3, page 469 to see an overview of the endocrine glands. They include
the following glands:
1.
hypothalamus;
6.
thymus;
2.
pituitary;
7.
adrenals;
3.
pineal gland;
8.
pancreas;
4.
thyroid;
9
.
testes;
5.
parathyroids;
10.
ovaries.
HORMONE ACTION
A.
General Characteristics:
1.
needed in very small amounts (potent);
2.
produce long-lasting effects in the cells they target;
3.
regulate metabolic processes (maintain homeostasis);
4.
are regulated by negative-feedback mechanisms;
B.
Chemistry of Hormones
may be steroid (produced from cholesterol = fat-soluble) or non-steroid (watersoluble). See Fig 13.4, page 470.
1.
A steroid hormone passes easily through the target cell membrane;
2.
A non-steroid hormone requires a receptor on the target cell
membrane to allow the hormone to enter the target cell.
II.
HORMONE ACTION
C.
Actions of Hormones – alter metabolic activity, only affect cells with receptor
1.
Steroid Hormones
a.
Enter cell by diffusion directly through cell membrane
b.
Bind to protein receptor
c.
Newly formed hormone-receptor complex alters gene expression
d.
New proteins carry out function signaled by hormone
2.
Non-steroid Hormones
a.
Includes amines, peptides, proteins and glycoproteins
b.
Hormone binds outside of cell and acts as first messenger
c.
Result is either increase or decrease in some second messenger
d.
Second messenger activates protein cascade,
leading to cellular changes
e.
Commonly G-protein regulated using cyclic
AMP as the second messenger.
See Figure 13.6 page 473 and
Fig 13.7 page 476.
D.
Prostaglandins
1.
2.
3.
III.
locally acting signals (paracrine)
varied functions
sometimes alter other hormones
CONTROL OF HORMONAL SECRETIONS
A.
Control Sources
1.
2.
Generally one or any combination of 3 types of control
a.
Hormonal control by tropic hormones of hypothalamus
b.
Nervous control by Autonomic nervous system
c.
Humoral control by regulating blood levels
See Figures 13.10 and 13.11 page 479 for set point and negative feedback
The overall scheme for the release of most hormones is presented in Figure 13.15, page
481 in the text. First of all, the HYPOTHALAMUS secretes "releasing hormones" that
target the anterior pituitary gland. See Fig 13.12, page 480.
IV.
GLANDS OF THE ENDOCRINE SYSTEM
A.
ANTERIOR PITUITARY GLAND (which hangs from the base of the brain and
sits in sella turcica (Fig 13.9, page 478) may then secrete 6 different hormones:
1.
Human Growth Hormone (HGH)
a.
controls growth of the body;
b.
targets bone, muscle and adipose tissue.
2.
Prolactin (PRL)
a.
b.
4.
Thyroid stimulating hormone (TSH)
a.
b.
4.
stimulates the production of milk by the mammary glands;
targets the mammary glands.
controls the secretion of hormones by the thyroid gland;
targets thyroid gland.
Adrenocorticotropic Hormone (ACTH)
a.
b.
controls the secretion of hormones by the adrenal cortex;
targets the outer portion of the adrenal gland (cortex).
5.
Follicle Stimulating Hormone (FSH)
a.
response depends upon sex:
o
In females, FSH stimulates maturation of an ovarian
follicle and ovum;
o
In males, FSH stimulates the maturation of sperm in the
testes;
b.
A gonadotropin, which targets primary sex organs (ovary & testis).
6.
Luteinizing Hormone (LH)
a.
response depends upon sex:
o
In females, LH causes ovulation;
o
In males, LH causes secretion of testosterone.
b.
A gonadotropin, which targets ovaries & testes.
IV.
GLANDS OF THE ENDOCRINE SYSTEM
B.
POSTERIOR PITUITARY GLAND
1.
2.
3.
4.
See Fig 13.12, page 480.
is located behind the anterior pituitary gland;
is continuous with nerve fibers (supraopticohypophyseal tract) of the
hypothalamus;
does not actually produce hormones (they are produced by the
hypothalamus), but stores them until it is stimulated to release them;
secretes 2 hormones: See Table 13.6, page 483.
a.
Antidiuretic Hormone (ADH):
o
targets distal convoluted tubules (of kidney);
o
causes DCT’s to reabsorb water back into the bloodstream,
and therefore controls water balance and (increases) blood
pressure.
b.
Oxytocin (OT):
o
targets uterine smooth muscle and breasts;
o
causes uterine muscle contraction and milk production.
c.
See Fig 13.17, page 483, comparing the structures of ADH & OT.
See Table 13.6, page 485, which summarizes the hormones of the pituitary gland.
C.
THYROID GLAND: See Fig 13.18 & 13.19, page 486.
1.
2.
3.
is located below larynx and around trachea;
is involved in iodine uptake (in order to produce thyroxine (T4) &
triiodothyronine (T3) below);
produces 3 hormones when stimulated by TSH:
See Table 13.7, p 487.
a.
Thyroxine (T4) & Triiodothyronine (T3):
o
increase basal metabolic rate by stimulating cellular oxygen
use to produce ATP;
o
regulate metabolism
o
See Fig 13.20, page 486.
b.
Calcitonin:
o
release is triggered by an increase in blood calcium levels;
o
targets bone cells (stimulates osteoblast activity and
inhibits osteoclast activity) & distal convoluted tubules
(causes secretion of excess calcium into urine);
o
Therefore, causes a decrease in blood calcium (and
phosphate) levels back to normal.
IV.
GLANDS OF THE ENDOCRINE SYSTEM
D.
E.
PARATHYROID GLANDS: See Fig 13.24 and 13.25, page 489.
1.
consist of 4 small glands;
2.
are located within the thyroid gland;
3.
produce a hormone called Parathyroid Hormone (PTH):
a.
release of PTH is stimulated by decreased blood calcium levels;
b.
PTH targets bone cells (activates osteoclasts to resorb bone),
proximal convoluted tubules (causes PCT’s to reabsorb calcium
back into bloodstream), and small intestine (promotes calcium
absorption, See Fig 13.26, page 490).
c.
Therefore, PTH causes an increase in blood calcium (and
phosphate) levels back to normal.
4.
PTH and calcitonin together maintain the homeostasis of Ca++ in the
blood.
a.
See Fig 13.26, page 490.
ADRENAL GLANDS
See Fig 13.28, page 491 and 13.29, page 492.
1.
are located atop the kidneys;
2.
are divided into an outer adrenal cortex and an inner adrenal medulla.
a.
Hormones of the Adrenal Medulla:
o
is located in the central portion of the adrenal glands;
o
produces 2 closely related hormones, which function in the
sympathetic division of the autonomic nervous system:
1.
epinephrine;
2.
norepinephrine.
a.
See Fig 13.30, page 492.
o
These hormones target:
1.
the heart (SA Node to increase heart rate);
2.
smooth muscle:
a. peripheral arterioles (vasoconstriction, which
increases blood pressure);
b. terminal bronchioles (bronchodilation, which
increases depth of breathing)
3.
the diaphragm (increased breathing rate).
See Fig 13.37, page 501, and Table 13.13, page 501,
concerning stress.
IV.
GLANDS OF THE ENDOCRINE SYSTEM
E.
ADRENAL GLANDS
b.
Hormones of the Adrenal Cortex: See Fig 13.28, page 491 and
13.29, page 492.
o
o
o
F.
PANCREAS:
a.
b.
c.
2.
e.
See Fig 13.34, page 497.
is located behind the stomach on the left side of abdomen;
functions as a mixed gland. (i.e. both an exocrine gland (digestion) and
endocrine gland (see below);
Hormones of the Pancreatic Islets (of Langerhans)
See Fig 13.35,
page 497, and Table 13.12, page 498.
1.
d.
is located in the outer portion of the adrenal glands;
produces many steroid hormones when stimulated by
ACTH:
See Fig 13.32, page 494, and table 13.11, page 495.
1.
Aldosterone targets proximal convoluted tubules,
causing reabsorption of water and electrolytes back
into the blood (increases blood pressure).
a.
See Fig 13.31, page 494.
2.
Cortisol targets all cells, where it regulates glucose
metabolism (along with T3 and T4).
a.
See Fig 13.33, page 495.
3.
Supplemental sex hormones (estrogens and
androgens) that target secondary sex organs.
Glucagon:
o
is produced by Alpha cells (α-cells) in Islets of
Langerhans;
o
Secretion is stimulated by decreased blood glucose levels
(i.e. fasting).
o
increases blood glucose levels (i.e. causes breakdown of
glycogen and release of glucose into bloodstream).
Insulin:
o
is produced by Beta cells (β-cells) in Islets of Langerhans;
o
Secretion is stimulated by increased blood glucose levels
(i.e. after eating).
o
decreases blood glucose levels (i.e. moves glucose from
bloodstream into cells and promotes glycogen formation in
liver and skeletal muscle).
See Fig 13.36, page 498 to review how these two hormones regulate
glucose homeostasis in the blood.
See Clinical Application 13.4, page 499, Diabetes Mellitus.
IV.
GLANDS OF THE ENDOCRINE SYSTEM
G.
THYMUS GLAND: See Fig 16.12, page 615.
1.
is located in the mediastinum region behind sternum;
2.
produces a hormone called thymosin that affects the maturation of
lymphocytes (T-cells);
3.
plays an important role in lymphatic system and immunity;
4.
decreases in size as we age.
H.
PINEAL GLAND: See Fig 13.3, page 469.
1.
is attached to the thalamus of the brain stem;
2.
secretes a hormone called melatonin:
a.
production is stimulated by daylight (circadian rhythm);
b.
affects moods, emotions, etc.
I.
OVARIES:
(will be discussed in greater detail in Chapter 22)
1.
An ovarian follicle (and ovum) start to mature each month
following puberty under the influence of follicle stimulating hormone
(FSH).
a.
The developing follicle secretes estrogen:
o
Estrogen develops female secondary sexual characteristics
(at puberty) and maintains them throughout life.
o
Estrogen targets:
1.
hair follicles in axillary and inguinal regions;
2.
mammary glands/ breasts;
3.
adipose tissue in hips, thighs, and buttocks.
2.
Luteinizing hormone (LH) causes the mature follicle to
rupture, releasing the ovum (ovulation).
o
a.
The follicle then becomes the corpus luteum.
The corpus luteum secretes progesterone:
1.
Progesterone
prepares the uterine lining for implantation of the
zygote.
J.
TESTES:
2.
(will be discussed in greater detail in Chapter 22)
1.
FSH targets the testes and causes the production of sperm.
LH targets the testes and causes the production of testosterone:
b.
a.
Testosterone
develops
male
secondary
sexual
characteristics at puberty and maintains them throughout life.
Testosterone targets:
o
hair follicles in facial axillary and inguinal regions;
o
muscle and bone;
o
vocal cords in larynx.
V.
HORMONE SUMMARY TABLE (Keyed at the end of this outline)
HORMONE
GH
TSH
PRL
ACTH
LH
FSH
T3/T4
ALDOSTERONE
CORTISOL
ESTROGEN
PROGESTERONE
TESTOSTERONE
ADH
OT
PTH
CALCITONIN
INSULIN
GLUCAGON
EPINEPHRINE
NOREPINEPHRINE
MELATONIN
THYMOSIN
SECRETED BY
WHAT GLAND?
TARGETS WHAT
GLAND OR
ORGAN OR
TISSUE?
EFFECT(S) AT
TARGET SITE
VI.
STRESS AND ITS EFFECTS
A.
Types of Stress
1.
Physical
a.
Injury = accidental
b.
Exercise = purposeful
2.
B.
VII.
Responses to Stress
1.
General Stress Syndrome is the hypothalamic response to stress
2.
Activates adrenal medulla via sympathetic nervous system – short term
3.
Activates adrenal cortex (cortisol) release in long term stress
4.
Basic goal is to increase available nutrients to fight off stress
HOMEOSTATIC IMBALANCES OF THE ENDOCRINE SYSTEM
(i.e. abnormal hormonal levels)
A.
VII.
Psychological
a.
Emotions = automatic
b.
Overloaded = can be self induced
Diabetes Mellitus
1.
See introduction on page 468.
2.
See Clinical Application 13.4, page 499.
3.
Symptoms (3 poly's): polyuria, polydypsia, polyphagia. Two types:
a.
Type I /IDDM (10%):
o
absolute insulin deficiency, with insulin administration.
o
Patients < 20 years;
o
autoimmune disorder where β-cells are destroyed;
o
Hyperglycemia results.
o
Cells can't use glucose so fat is broken down, releasing
ketone bodies, causing ketoacidosis, lowering blood pH,
and causing death.
o
Complications include Atherosclerosis, CV disease, IHD,
PVD, gangrene, blindness due to cataracts (lens) and retinal
vascular disease; renal failure.
o
Treatments:
1.
artificial pancreas that detects fall in glucose levels
and automatically releases insulin;
2.
transplant of pancreas or Beta cells.
b.
Type II/NIDDM (90%)
o
patients > 40 years,
o
overweight,
o
hypertension,
o
Problem is usually with receptors on target cells;
o
Controlled by diet, exercise, and weight loss;
o
Drug Diabeta (glyburide) may help stimulate insulin
secretion of β-cells (if low levels of insulin is the cause).
HOMEOSTATIC IMBALANCES OF THE ENDOCRINE SYSTEM
(i.e. abnormal hormonal levels)
B.
Growth Hormone Imbalances:
See Clinical Application 13.2, page 482.
1.
Pituitary Dwarfism = hyposecretion of GH during growth years.
a.
slow bone growth & closing of epiphyseal plates before normal
height is reached;
b.
Treatment = oral GH therapy.
2.
Pituitary giantism = hypersecretion of GH during growth
years.
a.
abnormal increase in the length of long bones.
3.
Acromegaly = hypersecretion of GH during adulthood.
a.
Bones of hands, feet, cheeks, and jaw thicken;
b.
Soft tissues also grow.
C.
ADH Imbalances: See blue box on page 484.
1.
Diabetes insipidus = hyposecretion of ADH.
a.
diuresis, dehydration, thirst;
b.
ADH in nasal spray.
D.
Thyroid Hormone Imbalances:
See Table 13.8, page 487.
1.
Cretinism = hyposecretion of T3/T4 during fetal life and infancy.
See Fig 13.11, page 479.
a.
dwarfism & mental retardation;
b.
prevention = newborn testing;
c.
treatment = oral thyroid therapy.
2.
Myxedema = hyposecretion during adulthood.
a.
edema, slow heart rate, low body temp, dry hair & skin, muscular
weakness, lethargy, weight gain;
b.
Oral thyroid hormones reduce symptoms.
3.
Grave's Disease = an autoimmune disorder that causes growth of thyroid
and hypersecretion of thyroid hormones, with no negative feedback.
a.
enlarged thyroid (2-3x larger);
b.
peculiar edema of the eyes (bulging);
c.
increased metabolic rate, heat intolerance, increased sweating,
weight loss, insomnia, tremor, and nervousness.
d.
treatment = surgical removal, use of radioisotopes to destroy some
of the thyroid. and anti-thyroid drugs to block synthesis of the
hormones.
e.
See Fig 13.22, page 488 and blue box on page 488 re: Bush family.
4.
Goiter = low thyroid hormones due to iodine deficiency.
a.
No thyroid hormones inhibit pituitary release of TSH;
b.
Thyroid is overstimulated and enlarges, but
still functions below normal levels.
c.
See Fig 13.23, page 488.
E.
Parathyroid Hormone Imbalances: See Table 13.9, page 490.
VII.
HOMEOSTATIC IMBALANCES OF THE ENDOCRINE SYSTEM
(i.e. abnormal hormonal levels)
F.
Adrenal Cortical Hormone Imbalances
1.
2.
See Clinical Application 13.3, p 496.
Addison's Disease = hyposecretion of AC hormones due to autoimmunity
or disease (TB).
Symptoms: mental lethargy, anorexia, nausea, vomiting, weight loss,
pigmentation.
Cushing's Syndrome = hypersecretion of AC hormones due to pituitary
tumor or steroid administration.
Symptoms: redistribution of fat, thin limbs due to wasting of muscles
(i.e. protein catabolism), "moon face", "buffalo hump",
"beer belly", stretch marks, bruises, poor wound healing,
hyperglycemia, osteoporosis, weakness, hypertension,
swings.
Usual cause: administration of steroids (i.e. prednisone) for transplant
patients, asthma, and chronic inflammatory disorders.
G.
Pineal Gland/ Melatonin Imbalances:
See blue box on page 500.
VIII.
LIFE SPAN CHANGES
Endocrine glands tend to shrink and accumulate fibrous connective tissue, fat, and
lipofuscin with age, but hormone levels usually remain within normal levels.
IX.
Innerconnections of the Endocrine System. See page 503.
X.
Clinical Terms Related to the Endocrine System. See page 504.
HORMONE SUMMARY TABLE
HORMONE
SECRETED BY
WHAT GLAND?
TARGET(S)?
EFFECT(S) AT
TARGET SITE
Growth Hormone (GH)
anterior pituitary
bone, muscle,
fat
growth of tissues
Thyroid Stimulating Hormone
(TSH)
anterior pituitary
thyroid
secrete hormones
Prolactin (PRL)
anterior pituitary
mammary
glands
produce milk
Adrenocorticotropic hormone
(ACTH)
anterior pituitary
adrenal cortex
secrete hormones
Luteinizing Hormone (LH)
anterior pituitary
In males:
interstitial cells
in testes;
in females:
mature
ovarian follicle
males: testosterone
secretion
females: ovulation
Follicle stimulating hormone
(FSH)
anterior pituitary
males: semiiferous tubules
of testes;
females:
ovarian follicle
males: sperm
production
females:
follicle/ovum
maturation
Triiodothyronine (T3) &
Thyroxine (T4)
thyroid
all cells
regulates rate of
metabolism
ALDOSTERONE
adrenal cortex
Proximal
convoluted
tubules
reabsorption of
water and Na
(increases blood
pressure)
CORTISOL
adrenal cortex
all cells
Rate of glucose
metabolism
ESTROGEN
ovarian follicle
secondary sex
organs
development at
puberty and
maintenance
throughout life
HORMONE
SECRETED BY
WHAT GLAND?
corpus luteum of
ovary
TARGET(S)?
TESTOSTERONE
seminiferous tubules
of testes
secondary sex
organs
development and
maintenance
Anti-Diuretic Hormone (ADH)
posterior pituitary
distal
convoluted
tubule (DCT)
reabsorption of
water ( increases
blood pressure)
Oxytocin (OT)
posterior pituitary
uterine smooth
muscle
contraction during
labor
Parathyroid Hormone (PTH)
Parathyroid
Proximal
kidney tubules,
osteoclasts,
intestine
reabsorption of Ca++
into blood, bone
resorption, dietary
Ca ++ absorption
(increases blood
Ca++)
CALCITONIN
thyroid
Distal
convoluted
tubules and
osteoblasts
secretion of Ca++
into urine, bone
formation (decreases blood Ca++)
INSULIN
β-cells of Pancreatic
Islets
all cells, liver
and skeletal
muscle
pushes glucose into
cells from blood,
glycogen formation
(decreases blood
glucose)
GLUCAGON
α-cells of pancreatic
Islets
liver and
skeletal muscle
breakdown of
glycogen (increase
in blood glucose)
EPINEPHRINE/
NOREPINEPHRINE
adrenal medulla
increases heart rate
and blood
pressure...
MELATONIN
pineal
cardiac muscle,
arteriole and
bronchiole
smooth muscle,
diaphragm, etc
limbic system
THYMOSIN
thymus
t-lymphocytes
Maturation
PROGESTERONE
uterine
endometrium
EFFECT(S) AT
TARGET SITE
preparation for
implantation
(thickens, etc)
Circadian rhythm,
emotions/behavior
Chapter 13: Endocrine System
I. General Characteristics of the Endocrine System
A. The endocrine glands secrete hormones.
B. Hormones diffuse from interstitial fluids into the blood stream and eventually act on
target cells.
C. Paracrine secretions are secretions that do not travel in the blood stream to their
targets.
D. Autocrine secretions are secretions that affect the secreting cell itself.
E. Exocrine glands secrete substances into ducts.
F. Endocrine glands and their hormones control metabolic processes.
G. Endocrine hormones also play vital roles in reproduction, development, and growth.
H. The larger endocrine glands are the pituitary, thyroid, parathyroids, adrenals, and
pancreas.
II. Hormone Action
A. Introduction
1. Hormones only affect their target cells.
2. Target cells have receptors for particular hormones.
B. Chemistry of Hormones
1. Introduction
a. Steroid hormones are synthesized from cholesterol.
b. Nonsteroid hormones are synthesized from amino acids.
2. Steroid Hormones
a. Steroids are lipids that include complex rings of carbon and hydrogen
atoms.
b. Examples of steroid hormones are testosterone, estrogen, aldosterone,
and cortisol.
3. Nonsteroid Hormones
a. Examples of hormones called amines are norepinephrine and
epinephrine.
b. Protein hormones are composed of long chains of amino acids.
c. Examples of protein hormones are those secreted by the anterior
pituitary and parathyroid glands.
d. Hormones called glycoproteins are produced by the anterior pituitary.
e. Peptide hormones are short chains of amino acids.
f. Peptide hormones come from the posterior pituitary and hypothalamus.
g. Prostaglandins are paracrine substances and are produced in a wide
variety of cells.
C. Actions of Hormones
1. Introduction
a. Hormones exert their effects by altering metabolic processes.
b. Hormones may reach all cells but only affect those that have
appropriate receptors.
c. The more receptors the hormone binds on its target cell, the greater the
response.
2. Steroid Hormones
a. Steroid hormones are insoluble in water but are soluble in lipids.
b. Steroid hormones can diffuse into cells relatively easily.
c. Once steroid hormones are inside a cell, they combine with specific
protein receptors located usually in the nucleus.
d. The binding of a steroid hormone to its receptor usually activates or
inhibits a gene.
e. Activated genes code for specific proteins.
f. The new proteins may be enzymes, transport proteins, or hormone
receptors and they bring about cellular changes.
3. Nonsteroid Hormones
a. A nonsteroid hormone usually binds with receptors located on the cell
membrane.
b. When a nonsteroid hormone binds to a membrane receptor, this causes
the receptor’s activity site to interact with other membrane proteins.
c. Receptor binding may alter the function of enzymes or membrane
transport mechanisms, changing the concentrations of still other cellular
components.
d. A first messenger is the hormone.
e. Second messengers are the chemicals in the cell that induce the changes
that are recognized as responses to the hormone.
f. Many hormones use cyclic AMP as a second messenger.
g. G proteins are activated by the binding of a hormone to a membrane
receptor.
h. Adenylate cyclase is activated by G proteins.
i. Adenylate cyclase functions to form cyclic AMP from ATP.
j. Cyclic AMP activates another set of enzymes called protein kinases.
k. Protein kinases function to transfer phosphate groups from ATP to
proteins substrate molecules.
l. Phosphorylated substrates may be converted from inactive to active
forms.
m. Activated proteins then alter various cellular processes to bring about
the effect of that particular hormone.
n. Hormones whose actions depend upon cyclic AMP include releasinghormones form the hypothalamus, TSH, ACTH, FSH, LH, ADH, PTH,
norepinephrine, epinephrine, glucagon, and calcitonin.
o. An example of another second messenger is DAG.
p. In another mechanism, a hormone binding to its receptor increases
calcium, ion concentration within the target cell.
q. Calcium ions bind to the protein calmodulin to activate it.
r. Activated calmodulin functions to interact with enzymes, altering their
activities.
s. Cells are highly sensitive to changes in concentration of nonsteroid
hormones because responses to them is greatly amplified through second
messengers.
D. Prostaglandins
1. Prostaglandins are paracrine substances that act locally.
2. Some prostaglandins regulate cellular responses to hormones.
3. The variety of effects prostaglandins can produce include relaxation of smooth
muscle in airway and blood vessels, contraction of smooth muscle in the uterus,
stimulation of secretion of various hormones, and promotion of inflammation.
III. Control of Hormonal Secretions
A. Introduction
1. Hormones are continually excreted in urine and broken down by enzymes in
the liver.
2. Increasing or decreasing blood levels of hormones requires increased of
decreased secretion.
B. Control Sources
1. The hypothalamus controls the anterior pituitary gland’s release of tropic
hormones.
2. Tropic hormones are those that stimulate other endocrine gland sto release
hormones.
3. An example of an endocrine organ directly stimulated by the nervous system is
the adrenal medulla.
4. Some endocrine glands respond to changes in the composition of the internal
environment.
5. As a result of negative feedback mechanisms, hormone levels remain relatively
stable.
IV. Pituitary Gland
A. Introduction
1. The pituitary gland is located at the base of the brain.
2. The infundibulum is a stalk that attaches the pituitary gland to the
hypothalamus.
3. The two portions of the pituitary are anterior and posterior.
4. The anterior lobe secretes the following hormones: GH, TSH, ACTH, FSH,
LH, PRL.
5. The posterior pituitary secretes the following hormones: OT and ADH
6. The hypothalamus controls most of the pituitary gland’s activities.
7. The posterior pituitary receives impulses from the hypothalamus.
8. Releasing hormones from the hypothalamus control the anterior pituitary.
9. The hypophyseal portal veins are vessels that pass downward along the
pituitary stalk from the hypothalamus and give rise to a capillary be in the anterior
lobe of the pituitary.
B. Anterior Pituitary Hormones
1. Somatotropes secrete GH.
2. Mammotropes secrete PRL.
3. Thyrotropes secrete TSH.
4. Corticotropes secrete ACTH.
5. Gonadotropes secrete FSH and LH.
6. Actions of growth hormone are stimulation of cells to enlarge and more
rapidly divide, enhance movement of amino acids through the cell membranes,
and increases the rate of protein synthesis. GH also decreases the rate as which
cells utilize carbohydrates and increases the rate at which cells use fats.
7. The secretion of GH is controlled by somatostatin and GHRH.
8. Actions of prolactin are to sustain mild production after birth and to amplify
effect of LH in males.
9. The secretion of PRL is controlled by PIH and PRF.
10. Actions of thyroid-stimulating hormone are to stimulate the thyroid gland to
release its hormones.
11. The secretion of TSH is controlled by TRH.
12. The actions of adrenocorticotropic hormone are to control secretion of certain
hormone from the adrenal cortex.
13. The secretion of ACTH is controlled by CRH.
14. Gonadotropins are LH and FSH.
15. The actions of follicle-stimulating hormone are to promote development of
egg-containing follicles in ovaries, to simulate follicular cells to releases estrogen,
and in male, to stimulate production of sperm cells.
16. The actions of luteinizing hormone are to promote secretion of sex hormones
and to promote the release egg cells in females.
17. The secretion of FSH and LH is controlled by GnRH.
C. Posterior Pituitary Hormones
1. The posterior pituitary consists of nerve fibers and neuroglial cells.
2. Specialized neurons in the hypothalamus produce two hormones called OT and
ADH.
3. The hormones produced in the hypothalamus travel down axons through the
pituitary stalk to the posterior pituitary.
4. The actions of antidiuretic hormone are to cause a reduction in water excretion,
and to raise blood pressure.
5. The secretion of ADH is controlled by blood water concentration and blood
volume.
6. The actions of oxytocin are to contact muscles in uterine wall and to contract
muscles associated with milk-secreting cells.
7. The secretion of oxytocin is controlled by uterine stretch and stimulation of
breasts.
V. Thyroid Gland
A. Introduction
1. The thyroid gland consists of two lobes.
2. The thyroid gland is located just below the larynx on either side and anterior to
the trachea.
B. Structure of the Gland
1. Follicles are secretory parts of the thyroid gland.
2. Colloid is a viscous fluid that fills follicles and contains thyroglobulin.
3. Thyroglobulin is a glycoprotein.
4. Extrafollicular cells are located outside of follicles.
5. The follicular cells produce hormones.
C. Thyroid Hormones
1. The three hormones produced by the thyroid gland are T4, T3, and calcitonin.
2. The actions of thyroxine and triiodothyronine are to regulate metabolism of
carbohydrates, lipids, and proteins.
3. The secretion of T3 and T4 are controlled by TSH.
4. Follicular cells require iodine to produce T3 and T4.
5. The actions of calcitonin are to lower blood calcium levels.
6. The secretion of calcitonin is controlled by blood calcium levels. It is released
in response to high blood calcium levels.
VII. Parathyroid Glands
A. Introduction
1. Parathyroid glands are located embedded in the thyroid gland.
2. Usually a person has four parathyroid glands.
B. Structure of the Glands
1. Each parathyroid gland is covered by a thin capsule.
2. The body of a parathyroid gland consists of many tightly packed secretory
cells.
C. Parathyroid Hormone
1. The actions of PTH are to raise blood calcium levels.
2. The secretion of PTH is controlled by blood calcium levels. It is released in
response to low blood calcium levels.
VIII. Adrenal Glands
A. Structure of the Glands
1. The adrenal glands are shaped like pyramids.
2. The two parts of an adrenal gland are the cortex and medulla.
3. The adrenal medulla consists of irregularly shaped cells grouped around blood
vessels.
4. The adrenal cortex is composed of closely packed masses of epithelial layers.
5. The three layers of the adrenal cortex are the outer zona glomerulosa, the
middle zona fasciculata, and the inner zona reticulairs.
B. Hormones of the Adrenal Medulla
1. The two hormones released by the adrenal medulla are epinephrine and
norepinephrine.
2. The actions of epinephrine and norepinephrine are increased heart rate,
increased force of cardiac muscle contraction, elevated blood pressure, increased
breathing rate and decreased activity of the digestive system
3. The secretion of epinephrine and norepinephrine are controlled by the
sympathetic nervous system.
C. Hormones of the Adrenal Cortex
1. Introduction
a. The adrenal cortex produces more than 30 different steroids.
b. The most important adrenal cortical hormones are aldosterone, cortisol,
and certain sex hormones.
2. Aldosterone
a. Aldosterone is secreted by the zona glomerulosa and is called a
mineralocorticoid because it helps regulate the concentration of mineral
electrolytes.
b. The actions of aldosterone are regulation of concentration of
extracellular electrolytes by conserving sodium ions and excreting
potassium ions.
c. The secretion of aldosterone is controlled by electrolyte concentrations
in body fluids and the renin-angiotensin mechanism
3. Cortisol
a. Cortisol is secreted by the zona fascilulata and is called a
glucocorticoid because it affects glucose metabolism
b. The actions of cortisol are to decrease protein synthesis, increase fatty
acid release, and simulate glucose synthesis from noncarbohydrates.
c. The secretion of cortisol is controlled by CRH.
4. Sex Hormones
a. The sex hormones are secreted by the zona reticularis.
b. The actions of the sex hormones are to supplement sex hormone from
the gonads.
c. Examples of sex hormones are androgens such as testosterone.
IX. Pancreas
A. Structure of the Gland
1. The pancreas is located posterior to the stomach.
2. The endocrine portion of the pancreas consists of islets of Langerhans which
are also called pancreatic islets.
3. Three cell types of the pancreatic islets are alpha, beta, and delta.
4. Alpha cells secrete glucagon.
5. Beta cells secrete insulin.
6. Delta cells secrete somatostatin.
B. Hormones of the Pancreatic Islets
1. The actions of glucagon are to stimulate the liver to break down glycogen and
to convert noncarbohydrates into glucose. It also simulated the breakdown of
fats.
2. The secretion of glucagon is controlled by blood glucose concentrations.
3. The actions of insulin are to promote the formation of glycogen from glucose,
to inhibit conversion of noncarbohydrates into glucose, and to enhance movement
of glucose through adipose and muscle cell membranes. It also decreases blood
glucose concentrations, promotes transport of amine acids into cells, and enhances
synthesis of proteins and fats.
4. The secretion of insulin is controlled by blood glucose concentrations.
5. The function of somatostatin is to help regulate carbohydrates.
X. Other Endocrine Glands
A. Pineal Gland
1. The pineal gland is located near the roof of the third ventricle.
2. The pineal gland produces the hormone melatonin.
3. The functions of melatonin are to help regulate circadian rhythms and to
inhibit secretion of gonadotropins.
B. Thymus gland
1. The thymus gland is located between the lungs.
2. The thymus gland secretes a group of hormones called thymosins.
3. The function of thymosin is to promote the maturation of T lymphocytes.
C. Reproductive Organs
1. Reproductive organs that secrete hormones are ovaries and testes.
2. Examples of hormones produced by reproductive organs are estrogen,
progesterone, and testosterone.
D. Other Hormone-Producing Organs
1. The hormone produced by the heart is ANP.
2. The hormone produced by the kidneys is erythropoietin.
XI. Stress and Its Effects
A. Introduction
1. A stressor is a factor capable of producing stress.
2. Stress is a protective response produced by the body in response to stress
factors.
B. Types of Stress
1. Examples of physical stress include extreme cold or heat, decreases oxygen
concentrations, infection, injuries, heavy exercise and loud sounds.
2. Examples of psychological stress are imagined dangers, personal losses,
unpleasant social interaction or any factor that threatens a person.
C. Responses to Stress
1. The general stress syndrome is a group of symptoms produced by the
hypothalamus in response to stress.
2. Major events of the general stress syndrome are increased blood glucose
levels, increased heart rate and breathing rate, dilation of airways, and shunting of
blood into muscles. See table 13.13.
XII. Life-Span Changes
A. General changes in the glands of the endocrine system are a decrease in size and
increase in the proportion of each gland that is fibrous in nature.
B. Treatments for endocrine disorders include supplements of hormones or removing
part of an overactive gland or using drugs to block the action of an overabundant
hormone.
C. Levels of ADH increase with age and as a result, the kidneys reabsorb more water.
D. The decrease of calcitonin levels with age increases the risk of osteoporosis.
E. The most obvious changes in endocrine function involve blood glucose regulation.
Chapter 13: Endocrine System
I. General Characteristics of the Endocrine System
A. The endocrine glands secrete _____________________________________________
B. Hormones diffuse from ________________________ into ______________________
___________________ and eventually act on __________________________________
C. Paracrine secretions are __________________________________________________
D. Autocrine secretions are _________________________________________________
E. Exocrine glands secrete substances into _____________________________________
F. Endocrine glands and their hormones control _________________________________
________________________________________________________________________
G. Endocrine hormones also play vital roles in __________________________________
________________________________________________________________________
H. The larger endocrine glands are ___________________________________________
________________________________________________________________________
II. Hormone Action
A. Introduction
1. Hormones only affect their _________________________________________
2. Target cells have ________________________ for ______________________
__________________________________________________________________
B. Chemistry of Hormones
1. Introduction
a. Steroid hormones are synthesized from __________________________
b. Nonsteroid hormones are synthesized from _______________________
2. Steroid Hormones
a. Steroids are ________________________________________________
b. Examples of steroid hormones are ______________________________
____________________________________________________________
3. Nonsteroid Hormones
a. Examples of hormones called amines are ________________________
____________________________________________________________
b. Protein hormones are composed of _____________________________
c. Examples of protein hormones are ______________________________
____________________________________________________________
d. Hormones called glycoproteins are produced by ___________________
____________________________________________________________
e. Peptide hormones are ________________________________________
f. Peptide hormones come from __________________________________
____________________________________________________________
g. Prostaglandins are ____________________________________ and are
produced ____________________________________________________
C. Actions of Hormones
1. Introduction
a. Hormones exert their effects by ________________________________
____________________________________________________________
b. Hormones may reach all cells but only affect _____________________
____________________________________________________________
c. The more receptors the hormone binds on its target cell, the greater ___
____________________________________________________________
2. Steroid Hormones
a. Steroid hormones are insoluble in ________________________ but are
soluble in ____________________________________________________
b. Steroid hormones can diffuse__________________________________
c. Once steroid hormones are inside a cell, they combine with __________
___________________ located _________________________________
d. The binding of a steroid hormone to its receptor usually ____________
or ____________________________________________________ a gene.
e. Activated genes code for _____________________________________
f. The new proteins may be _____________________________________
_____________________________ and they bring about cellular changes.
3. Nonsteroid Hormones
a. A nonsteroid hormone usually binds with receptors located __________
____________________________________________________________
b. When a nonsteroid hormone binds to a membrane receptor, this causes
the receptor’s activity site to ____________________________________
c. Receptor binding may alter ___________________________________
____________________________________________________________
d. A first messenger is _________________________________________
e. Second messengers are _______________________________________
f. Many hormones use _______________________________ as a second
messenger.
g. G proteins are activated by ___________________________________
h. Adenylate cyclase is activated by ______________________________
i. Adenylate cyclase functions to _________________________________
j. Cyclic AMP activates ________________________________________
k. Protein kinases function to ____________________________________
l. Phosphorylated substrates may be converted from__________________
to active forms.
m. Activated proteins then alter __________________________________
____________________________________________________________
n. Hormones whose actions depend upon cyclic AMP include __________
____________________________________________________________
o. An example of another second messenger is ______________________
p. In another mechanism, a hormone binding to its receptor increases ____
____________________________________________________________
q. Calcium ions bind to the protein ____________________ to activate it.
r. Activated calmodulin functions to ______________________________
s. Cells are highly sensitive to changes in concentration of nonsteroid
hormones because _____________________________________________
____________________________________________________________
D. Prostaglandins
1. Prostaglandins are ________________________________________________
2. Some prostaglandins regulate _______________________________________
__________________________________________________________________
3. The variety of effects prostaglandins can produce include _________________
__________________________________________________________________
III. Control of Hormonal Secretions
A. Introduction
1. Hormones are continually _____________________ in urine and broken down
_____________________________ in the_______________________________
2. Increasing or decreasing blood levels of hormones requires ________________
__________________________________________________________________
B. Control Sources
1. The hypothalamus controls _________________________________________
2. Tropic hormones are ______________________________________________
3. An example of an endocrine organ directly stimulated by the nervous system is
__________________________________________________________________
4. Some endocrine glands respond to changes in __________________________
__________________________________________________________________
5. As a result of ________________________________ , hormone levels remain
relatively stable.
IV. Pituitary Gland
A. Introduction
1. The pituitary gland is located ________________________________________
2. The infundibulum is _______________________________________________
3. The two portions of the pituitary are __________________________________
4. The anterior lobe secretes the following hormones: ______________________
__________________________________________________________________
5. The posterior pituitary secretes the following hormones: __________________
6. The ______________________ controls most of the pituitary gland’s activities.
7. The posterior pituitary receives impulses from __________________________
8. ____________________ from the hypothalamus control the anterior pituitary.
9. The hypophyseal portal veins are ____________________________________
__________________________________________________________________
B. Anterior Pituitary Hormones
1. Somatotropes secrete ______________________________________________
2. Mammotropes secrete _____________________________________________
3. Thyrotropes secrete _______________________________________________
4. Corticotropes secrete ______________________________________________
5. Gonadotropes secrete ______________________________________________
6. Actions of growth hormone are ______________________________________
__________________________________________________________________
7. The secretion of GH is controlled by __________________________________
__________________________________________________________________
8. Actions of prolactin are ____________________________________________
__________________________________________________________________
9. The secretion of PRL is controlled by _________________________________
__________________________________________________________________
10. Actions of thyroid-stimulating hormone are ___________________________
__________________________________________________________________
11. The secretion of TSH is controlled by ________________________________
__________________________________________________________________
12. The actions of adrenocorticotropic hormone are ________________________
__________________________________________________________________
13. The secretion of ACTH is controlled by ______________________________
__________________________________________________________________
14. Gonadotropins are _______________________________________________
15. The actions of follicle-stimulating hormone are ________________________
__________________________________________________________________
16. The actions of luteinizing hormone are _______________________________
__________________________________________________________________
17. The secretion of FSH and LH is controlled by _________________________
__________________________________________________________________
C. Posterior Pituitary Hormones
1. The posterior pituitary consists of ____________________________________
2. Specialized neurons in the hypothalamus produce two hormones called ______
__________________________________________________________________
3. The hormones produced in the hypothalamus travel down _________________
__________________________________________________________________
4. The actions of antidiuretic hormone are _______________________________
__________________________________________________________________
5. The secretion of ADH is controlled by ________________________________
__________________________________________________________________
6. The actions of oxytocin are _________________________________________
__________________________________________________________________
7. The secretion of oxytocin is controlled by ______________________________
__________________________________________________________________
V. Thyroid Gland
A. Introduction
1. The thyroid gland consists of ________________________________________
2. The thyroid gland is located _________________________________________
B. Structure of the Gland
1. Follicles are _____________________________________________________
2. Colloid is _______________________________________________________
3. Thyroglobulin is __________________________________________________
4. Extrafollicular cells are located ______________________________________
5. The follicular cells produce _________________________________________
C. Thyroid Hormones
1. The three hormones produced by the thyroid gland are ___________________
__________________________________________________________________
2. The actions of thyroxine and triiodothyronine are ________________________
__________________________________________________________________
3. The secretion of T3 and T4 are controlled by ____________________________
__________________________________________________________________
4. Follicular cells require ___________________________ to produce T3 and T4.
5. The actions of calcitonin are ________________________________________
__________________________________________________________________
6. The secretion of calcitonin is controlled by _____________________________
__________________________________________________________________
VII. Parathyroid Glands
A. Introduction
1. Parathyroid glands are located _______________________________________
2. Usually a person has ______________________________ parathyroid glands.
B. Structure of the Glands
1. Each parathyroid gland is covered by _________________________________
2. The body of a parathyroid gland consists of ____________________________
__________________________________________________________________
C. Parathyroid Hormone
1. The actions of PTH are ____________________________________________
__________________________________________________________________
2. The secretion of PTH is controlled by _________________________________
__________________________________________________________________
VIII. Adrenal Glands
A. Structure of the Glands
1. The adrenal glands are shaped like ___________________________________
2. The two parts of an adrenal gland are _________________________________
3. The adrenal medulla consists of______________________________________
__________________________________________________________________
4. The adrenal cortex is composed of ___________________________________
5. The three layers of the adrenal cortex are ______________________________
__________________________________________________________________
B. Hormones of the Adrenal Medulla
1. The two hormones released by the adrenal medulla are ___________________
__________________________________________________________________
2. The actions of epinephrine and norepinephrine are _______________________
__________________________________________________________________
3. The secretion of epinephrine and norepinephrine are controlled by __________
__________________________________________________________________
C. Hormones of the Adrenal Cortex
1. Introduction
a. The adrenal cortex produces more than ___________ different steroids.
b. The most important adrenal cortical hormones are _________________
____________________________________________________________
2. Aldosterone
a. Aldosterone is secreted by _______________________________ and is
called a mineralocorticoid because ________________________________
____________________________________________________________
b. The actions of aldosterone are _________________________________
____________________________________________________________
c. The secretion of aldosterone is controlled by _____________________
____________________________________________________________
3. Cortisol
a. Cortisol is secreted by __________________________________ and is
called a glucocorticoid because __________________________________
____________________________________________________________
b. The actions of cortisol are ____________________________________
____________________________________________________________
c. The secretion of cortisol is controlled by _________________________
____________________________________________________________
4. Sex Hormones
a. The sex hormones are secreted by ______________________________
____________________________________________________________
b. The actions of the sex hormones are ____________________________
____________________________________________________________
c. Examples of sex hormones are _________________________________
____________________________________________________________
IX. Pancreas
A. Structure of the Gland
1. The pancreas is located ____________________________________________
2. The endocrine portion of the pancreas consists of ________________________
__________________________________________________________________
3. Three cell types of the pancreatic islets are _____________________________
4. Alpha cells secrete ________________________________________________
5. Beta cells secrete _________________________________________________
6. Delta cells secrete ________________________________________________
B. Hormones of the Pancreatic Islets
1. The actions of glucagon are _________________________________________
__________________________________________________________________
2. The secretion of glucagon is controlled by _____________________________
__________________________________________________________________
3. The actions of insulin are ___________________________________________
__________________________________________________________________
4. The secretion of insulin is controlled by _______________________________
__________________________________________________________________
5. The function of somatostatin is ______________________________________
X. Other Endocrine Glands
A. Pineal Gland
1. The pineal gland is located _________________________________________
2. The pineal gland produces the hormone _______________________________
3. The functions of melatonin are ______________________________________
B. Thymus gland
1. The thymus gland is located ________________________________________
2. The thymus gland secretes a group of hormones called ___________________
3. The function of thymosin is _________________________________________
__________________________________________________________________
C. Reproductive Organs
1. Reproductive organs that secrete hormones are__________________________
__________________________________________________________________
2. Examples of hormones produced by reproductive organs are _______________
__________________________________________________________________
D. Other Hormone-Producing Organs
1. The hormone produced by the heart is _________________________________
2. The hormone produced by the kidneys is ______________________________
XI. Stress and Its Effects
A. Introduction
1. A stressor is _____________________________________________________
2. Stress is ________________________________________________________
B. Types of Stress
1. Examples of physical stress include __________________________________
__________________________________________________________________
2. Examples of psychological stress are _________________________________
__________________________________________________________________
C. Responses to Stress
1. The general stress syndrome is ______________________________________
__________________________________________________________________
2. Major events of the general stress syndrome are _________________________
__________________________________________________________________
XII. Life-Span Changes
A. General changes in the glands of the endocrine system are ______________________
________________________________________________________________________
B. Treatments for endocrine disorders include __________________________________
________________________________________________________________________
C. Levels of _________________________ increase with age and as a result, the kidneys
________________________________________________________________________
D. The decrease of calcitonin levels with age increases the risk of ___________________
E. The most obvious changes in endocrine function involve _______________________
________________________________________________________________________