Download Endocrine Physiology

Endocrine
System
I. Overview of the Endocrine System

Made up of GLANDS that release
hormones into the bloodstream
◦ Hormones are chemical "messengers"
that control numerous body functions
Allow for the maintenance of internal
homeostasis or the internal environment in
the body
 Allow the regulation of growth and
development of an organism.

A. Major Glands of the Endocrine System
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HYPOTHALAMUS and
PITUITARY are in the
brain
PARATHYROIDS are in
the neck and sit on the
THYROID
THYMUS is found behind
the breastbone
ADRENALS sit on the
kidneys
PANCREAS is in the
abdomen
TESTES are in the
scrotum and OVARIES are
in the hip area
B. Functions of Endocrine Glands

The ovaries in females and testes in males
are also endocrine glands.
C. Transport of Hormones
Hormones are transported throughout the
body by the bloodstream to ALL cells
 A given hormone usually affects only a
limited number of cells called target cells
 Only the TARGET CELLS with the
RECEPTOR for the hormone will be
affected by that hormone

 Activities
Controlled by Hormones
◦ Activities of entire organs
◦ Mood
◦ Growth and development
◦ Reproduction
◦ Sexual characteristics
◦ Usage and storage of energy
◦ Levels of fluid, salt and sugar in the
blood
II. Endocrine Glands
A. Pituitary Gland
 The
pituitary gland communicates with
the hypothalamus to control many body
activities
Tiny structure about the size of a grape at
the base of the brain
 Connected to the hypothalamus (“BRAIN”
of the brain)
 Master Gland
 Produces & secretes NINE hormones that
affects other glands and organs

1. Hormones of the Pituitary
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Somatotropin (GH)growth hormone; helps fat be
used for energy
Thyrotropin (TSH)stimulates growth of the
thyroid gland
Adrenocorticotropic
(ACTH)- stimulates
growth of the adrenal gland

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Follicle stimulating
(FSH) – growth of the
ovarian follicles, production of
estrogen in females; &
production of sperm in males
Luteinizing (LH) –
stimulates ovulation and
produces progesterone in
females
Oxytocin (pitocin) –
released during childbirth;
causes contraction of the
uterus during childbirth
2. Diseases of Pituitary
 Gigantism
 Over-secretion of
growth hormone prior
to puberty Long bone
growth is decreased
 Excessive growth of
long bones
 Treatment: drug
therapy to inhibit GH
release
 Dwarfism
 Under-production of growth
hormone during childhood
 Long bone growth is
decreased
 Body is proportioned and
intelligence is normal
 Treatment: early diagnosis
& injections of GH for 5 or
more yrs.
B. Thyroid Gland
 Butterfly shaped mass found
in front of the trachea;
shaped like an H
 The hormones produces by
the thyroid gland are
controlled by the TSH in the
pituitary gland
 Requires iodine to produce
its hormone which is found
in foods and salt
Thyroid Gland
1. Hormones of the Thyroid Gland
◦ Calcitonin – accelerates storage of
calcium in bones and lowers blood calcium
levels; 99% of calcium in the body is stored
in bones, necessary for blood clotting, and
holding cells together
2. Disease of the Thyroid Gland
 Graves Disease
◦ These are severe forms
◦ More common in women
◦ Symptoms: strained and tense facial
expression, nervous, irritability
◦ Goiter -due to iodine deficiency,
dry/itchy skin, dry/brittle hair,
constipation, muscle cramps
◦ Major cause due to inflammation of
the thyroid which destroys the ability
of the gland to make thyroxine
Cretinism
Develops early in infancy or childhood
 Lack of mental/physical growth resulting in
mental retardation and malformation
 Sexual development and physical growth
does not reach beyond 7-8 year old
children

C. Parathyroid Gland
Four small glands behind the
thyroid (size of grains of rice)
1. Hormone of the Parathyroid
Gland
 Parathormone (PTH) Regulates calcium in blood and
stimulates bone cells to break
down bone tissue and release
calcium/phosphates into the
blood
 Maintains proper levels of
circulating calcium
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2. Disease of Parathyroid
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Hyperparathyroidism
◦ Over-activity of parathyroid
resulting in increased calcium in
the blood
◦ Leads to kidney stones, GI
disturbances
◦ Bones become weak, deformed
and fracture easily because
calcium is drawn from the bone
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Hypoparathyroidism
◦ Under-activity of parathyroid
gland causing a low level of
calcium in blood
◦ Tetany, hyperirritability of
nervous system, twitching
◦ Death can occur if the larynx
and respiratory muscles are
involved.
D. Adrenal Gland
“Suprarenal” glands because found
above each kidney
 Helps the body prepare for and deal
with stress
1. Hormones of the Adrenal Gland
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Epinephrine & Norepinephrine
activates nervous system to act in
stress & causing “flight or fight”
syndrome
Adrenal Glands
2. Diseases of the Adrenal Gland
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Addison’s disease
◦ Excessive pigmentation,
low blood pressure when
standing, muscular
weakness/fatigue,
diarrhea, weight loss,
vomiting
E. Pancreas
Fish-shaped organ
behind stomach
 Exocrine - secretes
pancreatic juices that
are carried to small
intestines to aid in
digestion) and
 Endocrine gland produces insulin
needed for cells to
absorb sugar from the
blood

1. Hormones of the Pancreas
Insulin – metabolizes sugar
 Glucagon – maintains blood level of
glucose

2. Diseases of Pancreas
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Diabetes Mellitus
◦ Decreased secretion of insulin w/ affects metabolism of
carbohydrates, proteins, fats
◦ 2 types of D.M.
 Type 1: juvenile onset; genetic and virus factors that destroy
parts of the pancreas
 More severe, requires insulin injections
 Type 2: adult onset; most common in adults over 45,
overweight, heredity, certain ethnic groups
 Frequently occurs in obese adults and may not be insulin
dependent
◦ Hyperglycemia, weight loss, fatigue, slow healing of
skin infections and vision changes,
F. Thymus
Mass of tissue found under the
sternum
 Active in early life activating cells in
the immune system
 Atrophies during puberty
1. Hormone of the Thymus Gland
 Produces only one hormone –
thymosin which stimulates
production of antibodies in early
years
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Thymus Gland
G. Ovaries
Female sex glands
 Located behind pelvic
cavity
 Secretes hormones that
regulate menstruation and
secondary sexual
characteristics
1. Hormones of the Ovaries
 Estrogen – promotes
growth and development
of sex organs in female
 Progesterone –
maintains lining of the
uterus
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H. Testes
Male sex gland
 Located in scrotal sac
and suspended outside
the body
1. Hormone of the Testes
 Testosterone regulates sexual
characteristics of male
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III. Endocrine System Maintains
HOMEOSTASIS
The word homeostasis means “the
maintenance of stable internal conditions
in an organism”.
 Homeostasis is maintained through a
system called Negative Feedback

A. Negative Feedback Loop
Secretion of hormones operates on a “negative
feedback” system – under the control of the
nervous system
 Negative feedback occurs when there is a
decrease in hormone level which triggers a
response to increase the amount of hormone in
the blood
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 Through
negative
feedback, when the
amount of a particular
hormone in the blood
reaches a certain level,
the endocrine system
sends signals that stop
the release of that
hormone.
B. Pancreas & Negative Feedback
Functions as
both an exocrine
and endocrine
gland
 Secretes insulin
and glucagon to
regulate the
glucose (sugar)
levels in the
blood
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1. Steps to Negative Feedback Involving
the Pancreas
STEP 1: The pancreas releases insulin when
there is too much sugar in the blood.
 STEP 2: Insulin stimulates the liver to remove
sugar from the blood and store it as glycogen.
 STEP 3: When there is not enough sugar in the
blood, the pancreas releases glucagon.
 STEP 4: Glucagon signals the liver to release
glucose back into the blood
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C. Leptin & Negative Feedback
Another example of a feedback loop is
with the hormone leptin.
 Fat cells produce leptin when they are
filled.
 Leptin is transported in the blood to the
brain where it helps to suppress a person
appetite.
 When the fat is used, the amount of
leptin decreases, which causes the brain
to start to feel hunger again
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Individuals without
the gene to produce
Leptin
Negative Feedback
Insulin and Glucagon & Leptin are
examples of a negative feedback loop.
◦ One hormone causes the opposite
effect of another hormone.
 Both are used to maintain homeostasis
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