Download Chapter 9: The endocrine system

Chapter 9: The endocrine system
Bio 24
The endocrine system
• One of two communication
systems in the body
• Consists of hormones:
chemicals secreted into the
blood that travel
throughout the body to act
on specific target cells
• Only cells with the
appropriate receptors will
respond to the hormonal
signal
Functions of the endocrine system
• Hormones are essential for:
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reproduction
regulation of the immune system
utilization of energy
maintenance of bone and muscle mass
growth
regulation of salt and water balance and blood
pressure
– regulation of our moods & emotions
– many other things!
The endocrine vs. the nervous system
Endocrine system
• uses chemical signals
• chemical signals
secreted into the blood
• effects take minutes or
hours and may be longlasting
Nervous system
• uses chemical and
electrical signals
• chemical signals travel
only across a synapse
• effects take a fraction of
a second and usually
mediates rapid
responses
2 main categories of hormones
• Amino acid-based hormones (most common)
include proteins, peptides, and amino acid
derivatives
– Include insulin, growth hormone, thyroid hormones
• Steroid hormones are small lipid molecules made
from cholesterol that can cross cell membranes
– Include testosterone, estrogen, progesterone, and
cortisol
Steroid hormone action
Nonsteroid hormone action uses
second messengers in the cell
Control of hormone release
• Release of most
hormones is controlled
by other hormones
• Hormones that control
the release of other
hormones are called
tropic hormones
Control of hormone release
• Some hormones are
released in response to
humoral stimuli:
substances in the blood
that are not hormones
Control of hormone release
• Release of some
hormones is controlled
by the nervous system
• The nervous and
endocrine systems
often work together in a
coordinated fashion
THE MAJOR ENDOCRINE ORGANS
Endocrine organs
• Most hormones are
released from epithelial
cells that form
endocrine glands
• Major ones are shown
here
The hypothalamus is the master
controller through the pituitary glands
Hormones of the anterior pituitary:
growth hormone
• Growth hormone
promotes growth of
bones and muscles in
children, and
maintenance of muscle
mass in adults
• Growth hormone excess
can result in gigantism
(if in childhood) or
acromegaly (if in
adulthood)
Hormones of the anterior pituitary:
prolactin
• Stimulates and
maintains milk
production
• Men make it, too, but
function is unknown!
Hormones of the anterior pituitary:
adrenocorticotropic hormone (ACTH)
• ACTH is a tropic hormone
that regulates the activity of
part of the adrenal glands
called the adrenal cortex
• Glucocorticoids released
from the adrenal cortex
increase blood glucose and
are involved in our stress
response; mineralocorticoids
regulate salt and water
balance by controlling urine
composition
Hormones of the anterior pituitary:
follicle-stimulating hormone (FSH) and
luteinizing hormone (LH)
• Both these hormones control the hormonal
activity of the gonads: testes and ovaries
• Both are essential for the development of
both sperm and eggs
Hormones of the anterior pituitary:
Thyroid-stimulating hormone (TSH)
• TSH influences the growth
of and hormone release
from the thyroid gland
• The thyroid gland releases
thyroid hormones, which
contain amino acid-like
molecules bound to iodine
atoms and also calcitonin,
which regulates calcium
deposition in bones
Structure of the thyroid
Thyroid hormone targets
• Thyroid hormones act on essentially every cell
in the body
• Control metabolic rate and energy utilization
• Also important for normal growth and
development and reproductive function
• Thyroid disease is quite common!
Thyroid deficiency
• Hypothyroidism (underactive thyroid) is most
often caused by autoimmune disease that attacks
the thyroid
• Symptoms include fatigue, persistent feeling of
cold, bloating and weight gain, dry skin, and
mental slowness
• Can be very well treated by taking thyroid
hormone pills
• Thyroid deficiency in children can cause mental
retardation and dwarfism, known as cretinism
Thyroid excess
• Hyperthyroidism (overactive
thyroid) can also result from
autoimmune disease or a
benign tumor of the thyroid
• Graves’ disease is one form
of hyperthyroidism that also
causes exophthalmos
(bulging eyes)
• Symptoms include rapid
heart rate, heat intolerance,
and nervous behavior
• Hyperthyroidism is harder to
treat
Goiter
• A goiter is an enlarged
thyroid
• Can be caused by
hyperthyroidism or
hypothyroidism
• Traditionally caused by
dietary iodine
deficiency