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The
Endocrine
System
The Endocrine System
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Endocrine cells release hormones into the
bloodstream
Hormones go throughout the body and affect
many tissues and organs at the same time
Effects are slow to appear and last a long time
even if there is no additional hormone released
Hormones control many long term processesi.e. development of embryo, growth, sexual
maturation, reproduction
Endocrine vs. Exocrine Glands
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Endocrine
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Produce hormones
Hormones released
directly into bloodstream
No ducts
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Exocrine
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Produce a variety of
secretions
Release secretion to a
surface (internal and
external)
Have ducts
Endocrine System vs Nervous System
Both are control systems for the body.
How are they different?
 Endocrine
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Slow acting
Long duration
Targets all tissues and
cells
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Nervous
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Quick acting
Short duration
Targets specific cells
Hormones
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Control many long term processes
Many chemicals act as both hormones and
neurotransmitters
Adrenal medulla and hypothalamus have both
endocrine and nervous functions
Most are either peptide hormones (protein based)
or steroids (lipid based)
Hormones work by changing types, action,
amount or properties of enzymes
Endocrine Reflexes
 Simplest
functional unit of endocrine
system
 Similar to the reflex arcs in the
nervous system
Endocrine Reflexes
Simplest endocrine reflexes
 Disturbance in homeostasis
endocrine
response
homeostasis restored
 More complex require more steps:
 Disturbance in homeostasis
activates the
pituitary gland messenger to another
gland response restore homeostasis
(examples: blood sugar and pancreas)
Endocrine Reflexes (continued)
Pituitary = “master gland”
 The most complex endocrine reflexes
involve the hypothalamus
 Disturbance in homeostasis
activates the
Hypothalamus pituitary targets a specific
gland
stimulates a response
homeostasis is restored
Hypothalamus
Main connection of nervous
and endocrine systems
 3 functions:
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Controls sympathetic output of adrenal medulla
Acts as endocrine gland—releases hormones
into the posterior pituitary gland
Secretes hormones that control activity of the
anterior pituitary
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Releasing hormones
Inhibiting hormones
Pituitary Gland (Master Gland)
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Also known as Hypophysis
2 parts—anterior and
posterior
9 hormones come from
pituitary gland
(all peptide)
Posterior Pituitary
Neurohypophysis
 2 Hormones:
 1. ADH (antidiuretic hormone
/vasopressin)-decreases water loss
from the kidneys, constricts peripheral
vessels ( increases blood pressure)
Diabetes insipidus- posterior pituitary releases too little
ADH so too much water is lost. Person is always thirsty.
Fluid is not kept in the system. Can lead to severe
dehydration and death. Treatment: synthetic ADH
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Posterior Pituitary
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2. Oxytocin (quick childbirth)
causes smooth
muscles to contract and
causes contraction of cells
surrounding the secretory
cells in mammary glandsoxytocin involved in child
birth and breast feeding
Anterior Pituitary
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Adenohypophysis
7 hormones
1. TSH- Thyroid
stimulating hormonecauses the release of
thyroid hormone
Anterior Pituitary
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2. ACTH- adrenocorticotropic
Hormone- releases steroid hormones
from the adrenal glands, especially
those for glucose metabolism
(glucocorticoids)
3. FSH- Follicle stimulating hormone.
In females causes egg development
and promotes estrogen release. In
males involved in sperm production
Anterior Pituitary
4. LH- Lutenizing hormone. In females
causes ovulation and promotes secretion of
progesterone (preparation for pregnancy)
In males-called interstitial cell stimulating
hormone (ICTH)-stimulates production of
androgens (male hormones)
FSH and LH= gonadotroic hormones
(gonadotropins)-regulate the gonads
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Anterior Pituitary
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5. Prolactin – involves in the development
of mammary glands and milk production.
6. GH- Growth Hormone- also known as
human growth hormone. Especially targets
skeletal muscle and cartilage cells.
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Pituitary Dwarfism-too little GH production
Giantism- too much GH before puberty
Anterior Pituitary
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7. MSH-Melanocyte Stimulating Hormoneincreases production of skin pigment
ACTH
GH
TSH
prolactin
LH
FFSH
MSH –skin
Pineal Gland
Parathyroid
Glands are not
shown—found
on the back of
the Thyroid
Pituitary
Gland
Anterior Pituitary
Posterior Pituitary
Thyroid Gland
Thymus
Adrenal Gland
Pancreas
Ovary
Testes
Thyroid Gland
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On the trachea (windpipe) under the thyroid
cartilage
Shaped like a butterfly
Thyroid follicles release hormones into the
bloodstream
Thyroid Hormones
Thyroxine (T4)-causes gradual,
long term increase in metablolism.
Accounts for 90% of thyroid
secretions
 Triiodothyronine (T3) causes a
strong, immediate increase in
cellular metabolism short lasting
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Thyroid Hormones
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Thyroid hormone functions:
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cellular metabolism and temperature, O2 and energy
use
heart rate and blood pressure
Stimulate formation of RBCs
Stimulate activity of other endocrine tissues
Accelerate turnover of minerals in bones
Maintain respiratory sensitivity to changes in O2 and CO2
levels
Allows us to adapt to cold temperatures by
metabolism and O2 consumption
Thyroid Disorders
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Hypothyroidismhormones
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production of thyroid
Infants- leads to inadequate skeletal and nervous
development, metabolic rate up to 40% below
normal
Later childhood-retards growth, delays puberty
Adults- lethargic, can’t adjust to the cold
Signs/Symptoms- dry skin, hair loss, slow reflexes,
low body temp., intellectual slowness
Treatment: synthetic thyroid hormones
Thyroid Disorders
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Hyperthyroidism-too much thyroid hormone
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Metabolic rate, perspiration, BP, and irregular
heart beat, skin becomes flushed
Restless, excitable, mood shifts
Very little reserve energy and fatigues easily
Thyroid Disorders
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Goiter- enlarged thyroid gland
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Caused by increase of thyroid follicle size from low
amounts of iodine in diet.
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Salt has added iodine
Graves Disease-excess thyroid activity leading to
goiter, leading to symptoms of hyperthyroidism
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Bulging eyes
More common in women- has genetic base
Treatment: anti-thyroid drugs, removal or destruction of
part of the thyroid(surgically or radioactive iodine)
Parathyroid Glands
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4 tiny glands—2 on each side of posterior thyroid
Hormone = parathormone
Regulates calcium
concentration in
blood and other
body fluids (increases
Calcium concentration)
Thymus
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Located in thoracic cavity behind sternum
Gets larger until puberty, then atrophies
Hormone—thymosin—important for normal
immune system (T Cells)
Adrenal Glands
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Cap on top of each kidney
Each adrenal gland surrounded by a
capsule
2 parts:
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Adrenal Cortex
Adrenal Medulla
Adrenal Cortex
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Outer part
Stores lipids
Produces many steroid hormones—
adrenocorticosteroids or corticosteroids
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Necessary for life
3 zones produce different types:
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Androgens, glucocorticoids (incl. cortisone and
cortisol), mineralocorticoids
Adrenal Cortex (continued)
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1. Androgens—male hormones
2. Glucocorticoids—affect glucose metabolism
 reduce inflammation throughout the body.
Example: Cortisol is a naturally occurring GC
that is made by your adrenal glands, and works
to regulate inflammation and other processes in
your body.
 Cushing’s Disease-overproduction of
glucocorticoids leads to exaggerated response to
stress, energy reserves moved around. Body fat
changes-(moon face), muscles break down
Adrenal Cortex (continued)
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3.Mineralocorticoids-effect electrolyte
composition of body fluids
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Hormone=aldosterone
Addison’s Disease-inadequate secretion of both
glucocorticoids and mineralocorticoid
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Signs/symptoms: hypoglycemia, weakness, can’t
mobilize energy reserves, can’t tolerate stress,
can cause sharp and fatal fall in blood pressure,
increased skin pigmentation
Adrenal Cortex (continued)
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Androgenital Syndrome-tumors that cause
overproduction of androgens
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Women develop male secondary sex
characteristics(hair patterns, muscle
development, fat distribution
Men it is called gynecomastia
(gyne=women,mast=breast). Development of
female secondary sexual characteristics
Adrenal Medulla
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Inner part of adrenal glands
2 hormones—epinephrine (adrenalin) and
norepinephrine (noradrenalin)
Epinephrine
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75-80% of adrenal medulla secretions
Increase cardiac activity, BP, glycogen breakdown,
increases blood glucose. Causes adipose tissue to
release lipids.
Norepinephrine
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Causes blood vessels to constrict and heart rate to
increase
Steroid Abuse
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Used to increase muscle size and strength
Results:
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heart disease and heart attacks
liver disease
stroke
atrophy of testes and decreased sperm count
decreased production of testosterone
immune system depression
“roid rages”
acne
hair loss
Pancreas
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Lumpy, pink organ near
the connection between
the stomach and small
intestine
Both exocrine and endocrine functions
Pancreas (continued)
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Exocrine function
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Produces digestive enzymes
Endocrine function
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Pancreatic islets (islets of
Langerhans) produce glucagon (alpha cells) and
insulin (beta cells) which work together to
regulate blood glucose
Hypoglycemia-low blood glucose
Diabetes Mellitus
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Hyperglycemia = high blood
glucose
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Leads to glycosuria and polyuria
2 types of Diabetes mellitus
Type 1 Diabetes = Insulin Dependent
Diabetes Mellitus (IDDM). Pancreas does
not produce enough insulin
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Fatal without insulin therapy and dietary control
Treatment: insulin injections plus diet and
exercise
Diabetes Mellitus (continued)
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Type 2—Non Insulin Dependent Diabetes
Mellitus (NIDDM)—pancreas produces
insulin, but peripheral tissues do not
respond appropriately
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Treatment: weight loss, diet,
oral medications
Three times as common as
IDDM
Diabetes Mellitus (continued)
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Complications
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Diabetic retinopathy- changes to blood vessels in the
retina
Diabetic nephropathy- kidney disease
Diabetic neuropathy- disturbance to blood supply to neural
Degenerative problems with cardiac circulation leading to
heart attacks
Peripheral vascular changes leading to decreased blood
flow to the feet that can lead to sores and amputation
Testes
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Male
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Cells in testes produce androgens (testosterone
is most important) which are responsible for:
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Functional sperm
Secondary sex
characteristics and
associated behaviors
Protein synthesis
Muscle growth
Ovaries
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Female:
Ovarian follicles = place
eggs (ova) develop
FSH causes follicles to
produce estrogens which
are responsible for:
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Maturation of ova
Growth of uterine lining
Female secondary sex characteristics
Ovaries (continued)
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LH causes ovulation
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Corpus Luteum = follicle after ovulation
Causes release mix of estrogens and
progesterone
Progesterone:
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Moves fertilized egg along fallopian tubes
Prepares uterus for implantation
Prepares mammary glands for lactation
In pregnancy—placenta works as
endocrine gland
Pineal Gland
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Location = roof of thalamus
Hormone = melatonin—inhibits melanin
production
Melatonin production increases at night and
decreases in daylight
Involved in the establishment of circadian
rhythms
Seasonal Affective Disorder (SAD)
Pineal Gland (cont.)
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Seasonal Affective Disorder (SAD)
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Happens in December through March when
daylight hours are fewer and melatonin
production increases
More common in northern latitudes
Causes depression, lethargy, decreased
concentration, over eating, over sleeping, may be
responsible for increased suicides
Stress
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Stress = any threat to homeostasis
General Adaptation Syndrome (GAS)—
body’s response to stress regardless of
source
3 phases:
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Alarm phase
Resistance phase
Exhaustion phase
General Adaptation Syndrome
(GAS)
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3 Phases
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1. Alarm phase- fast response directed by sympathetic division
of ANS. Energy reserves mobilized (glucose) to get the body
ready. Epinephrine is main hormone- fight or flight
2. Resistance phase- Long term adjustments. Happens if stress
lasts longer than a few hours (severe illness, severe anxiety,
starvation, etc) Glucocorticoids are primary hormones although
others are also involved. Lipid and protein reserves mobilized;
glucose levels increase, stable glucose conserved for neural
tissue
General Adaptation Syndrome
(GAS)
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3. Exhaustion phase- collapse of vital
systems. Eventually homeostatic regulation
breaks down. Nerve and muscle cells
malfunction. Causes: exhaustion of lipid
reserves, can’t produce glucocorticoids.
Vital organs are damaged. Death will
happen without immediate steps taken to
correct the problem
Hormones and Behavior
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Sex hormones at puberty
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Hormones can effect ability to learn,
memory, intellect, emotional state
Decrease of sex hormones at menopause
and male climacteric
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More aggressive, assertive
Mood swings
Mood swings
“Roid Rages”
Hormones and Aging
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Few changes to hormones with aging
except for reproductive hormones
(decrease)
Tissues may become less responsive to
hormones with age.