The Endocrine System
The Endocrine System
• Chemical messages (hormones) are
released into the bloodstream
• Some of the major processes controlled by
hormones include…
– Reproduction
– Growth and Development
– Body Defense
– Maintaining Homeostasis
– Regulating Metabolism
What are Hormones?
• Hormones are produced
by specialized cells
• Cells secrete hormones
into extracellular fluids
(blood, lymph)
• Blood transfers hormones
to target sites
• These hormones regulate
the activity of other cells!
What are Hormones?
• Two major chemical classifications of
hormones
– Amino acid-based hormones
• Examples: proteins, peptides, amines
– Steroids: made from cholesterol
What do Hormones cause?
•
•
•
•
Synthesis of proteins, such as enzymes
Activation or inactivation of enzymes
Stimulation of mitosis
Changes in the plasma membrane
• These changes all have one common goal
– to cause some larger, long-lasting
change in the body!
What causes Hormones to be
Released?
• Some sort of stimulus
will trigger hormones
to be released!
– Hormonal Stimulus
• Some hormones
released will
stimulate other
hormones to be
released
What causes Hormones to be
Released?
– Humoral Stimulus
• Changing blood levels of
ions & nutrients will
stimulate hormones to be
released
• Examples: Parathyroid
hormone (PTH) will cause
calcium to be released
from bone into blood, ADH
will cause water to be
reabsorbed into blood
What causes Hormones to be
Released?
– Neural Stimulus
• Nerve fibers stimulate
hormones to be
released
• Examples:
norepinephrine and
epinephrine released
during stress
What are
some of
the major
endocrine
organs?
Endocrine Organs
• Hypothalamus
– Found in brain
– Releases hormones that regulate the pituitary
gland
Endocrine Organs
• Pituitary Gland
– Hangs from hypothalamus, broken into two
lobes
– Releases hormones to control other glands
– Hormones released by the two lobes
include…
Pituitary Gland
– Posterior Lobe
• Oxytocin: contraction of uterus, release of milk
• Antidiuretic hormone (ADH): reabsorption of water
by kidneys
– Anterior Lobe
• Prolactin: milk production (pro= for; lact = milk)
• Follicle-Stimulating Hormone (FSH):
– In females, stimulates development of follicles in the
ovaries.
» You will soon learn that a follicle consists of follicle
cells and the developing egg
– In males, FSH stimulates sperm development within the
testes
• Lutenizing Hormone (LH):
– In females, triggers ovulation and the production of
progesterone and some estrogen
– In males, stimulates testosterone production and release
of sperm
Pituitary Gland cont
• Thyroid Stimulating Hormone (TSH): stimulates
thyroid gland
• Growth Hormone (GH): stimulates growth,
especially of bones and muscles
Endocrine Organs
• Gigantism
– Most of the tallest people in the world are so
because they have a tumor on their pituitary
gland
– This causes an overproduction of GH
Leonid Stadnyk – 8 ft 5 in
Robert Wadlow – 8 ft 11 in
• Tallest man ever on
record
• Lived to be only 22
Endocrine Organs
• Pineal Gland
– Found in brain
– Produces Melatonin, which helps establish
day/night cycle
Endocrine Organs
• Thyroid Gland
– Found at base of throat
– Produces Thyroid Hormone, which controls
the rate at which glucose is used & converted
to body heat and energy
Endocrine Organs
• Hyperthyroidism: overactive thyroid
– Produce too much thyroid hormone
– Symptoms include increased heart beat,
tremors, weight loss, and diarrhea
• Hypothyroidism: underactive thyroid
– Produce too little thyroid hormone
– Can be brought on by iodine deficiency or
genetics
– Symptoms include poor muscle tone, fatigue,
decreased heart beat, weight gain, and
constipation
Thyroid Gland Continued*
• A second important hormone produced by
the thyroid is called calcitonin
– Causes calcium to be deposited into the
bones
*please add these notes to your packet o notes
Endocrine Organs
• Parathyroid
– Tiny gland masses on the back of the thyroid
gland
– Produces Parathyroid Hormone (PTH), which
controls calcium release from the bones into
the blood
– *PTH is a hypercalcemic hormone (increases
blood levels of calcium) whereas calcitonin is
a hypocalcemic hormone.
Endocrine Organs
• Thymus
– Sits right above heart in the upper chest
– Produces Thymosin, which helps mature T
cells (immunity)
Endocrine Organs
• Adrenal Glands
– Sits on top of the kidneys
– Produce Aldosterone, which helps with water
balance of urine/blood
– Produce Glucocorticoids, which increase
blood glucose levels
– Produce Epinephrine/Norepinephrine, which
helps with short-term stresses
– Some sex hormones also made here
Endocrine Organs
• Pancreas
– Located at curvature of duodenum just
underneath the stomach
– While produces enzymes that help with
digestion, it also produces hormones such
as…
– Insulin, which increases ability of cells to
transport glucose across their plasma
membranes, thereby reducing glucose levels
of blood
Diabetes
• There are generally two types of diabetes
• Type 1/ Juvenile
– Pancreas self-destructs, causing lack of production
of insulin.
• Without insulin, sugar can not be absorbed by the body
– Symptoms of Type 1 diabetes (when not treated!)
are
• Very high blood sugar
• Weight loss
• 3 ‘Ps’
– Polydipsia - Excessive thirst
– Polyphagia - Excessive hunger
– Polyuria - Excessive urination
Type 1
– Treatment of Type 1 diabetes
• Diet
• Daily Insulin Injections
– Or
--
• Insulin pump that continuously releases insulin into
body.
Diabetes
• Type 2 / Adult Onset
– Body cells become resistant to insulin
• Or
– Pancreas is not producing enough insulin
– Symptoms of Type 2 diabetes (when not treated)
are
• Moderately high blood glucose levels
• Polydipsia, Polyphagia & polyuria (3Ps)
– When glucose flushes out of body along with water, resulting
dehydration.
• Because glucose is unavailable, the body will use fats
and proteins for energy instead which can cause weight
loss.
Diabetes
– Treatment of type 2 diabetes
• Diet
– Reduce the amount of sugar in diet and encourage
weight loss
• Oral medications that help
– increase absorption of sugar
– increase production of insulin
– decrease release of internal glucose stores
• Lastly, insulin injection if all above fail.
Endocrine Organs
• Gonads
– Male: Testes
• Produces Androgen hormones (especially
Testosterone), which promotes male sex
characteristics and helps sperm production
• Stimulated to be released b/c of LH
– Female: Ovaries
• Produces Estrogen, which promotes female sex
characteristics, stimulates growth of uterine lining
• Stimulated to be released b/c of FSH
• Produces Progesterone, which stimulates growth
of uterine lining