Download Endocrine System and Hormone Activity

Chapter 9: Endocrine System
and Hormone Activity
Homeostatic Control through Hormone Release
Overview
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Coordinates and directs
the activity of cells.
Interacts with the nervous
system.
Uses chemical
messengers called
hormones.
Controls a variety of
necessary biological
functions such as:
*Reproduction
*Growth and Development
*Defense
*Balance of fluids and
electrolytes
Mechanism of Action
• Hormones only affect certain tissues or
organs:
• Hormones bind only to specific sites on
the plasma membrane of those Target
cells:
Receptors
• The Target cell becomes active once the
hormone is bound to its specific receptor.
Classifications
Amine/Peptide
• Chemical base is 1+ Amino Acids.
• Acts by binding to receptor on cell surface
and activating an enzyme within the
cytoplasm.
• Does NOT enter the cell; remains on the
outside of the cell membrane.
Lipid/Steroid
• Chemical base is lipid/fat.
• Enters the cell membrane and nucleus of
the Target cell because like dissolves
like.
• Acts by directly activating a specific gene
in the nucleus of the cell.
Direct Gene Activation
Second Messenger System
Hormone Action:
What can hormones do?
• Change the permeability or electrical
state of the cell membrane.
• Synthesize molecules in the cell.
• Activate/Inactive enzymes.
• Stimulating, slowing or stopping
mitosis
Control of Hormone Release
Negative Feedback Mechanisms
regulate the blood levels of most
hormones in 3 ways:
1. Hormonal stimuli
2. Humoral stimuli
3. Neural stimuli
Hormonal Stimulation
• One hormone triggers the release of
another hormone.
• These trigger hormones are
TROPHIC HORMONES.
• Released by the Pituitary Gland in
the brain.
Humoral Stimulation
• Blood levels of chemicals triggers
the release of specific hormones.
Neural Stimulation
• Nerve fibers (Autonomic Sensory
Receptors) trigger the release of
specific hormones.
Pituitary Gland
“The Master Gland”
• 2 Functional Lobes
*Anterior Lobe
*Posterior Lobe
• Interacts closely with the
Nervous System
through the
hypothalamus.
• Protected by what
structure?
Anterior Pituitary
• Regulated through humoral
stimulation from the hypothalamus.
• Many of the hormones released are
Trophic Hormones.
Anterior Pituitary
Hormones
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Growth Hormone (GH)
Thyroid Stimulating Hormone (TSH)
Adrenocorticotropin Hormone (ACTH)
Follicle Stimulating Hormone (FSH)
Luteinizing Hormone (LH)
Melanocyte Stimulating Hormone
(MSH)
• Endorphins
Too Much Growth Hormone
• Acromegaly is caused by
too much growth hormone
AFTER puberty has
completed.
• Gigantism is caused by too
much growth hormone during
adolescence and puberty.
Too Little Growth Hormone
• The girl below is pictured
with her father at the age of
5 years.
• The man on the left is
25 years old. The man
on the right is 22 years
old.
Abnormal TSH secretion
• Exopthalmosis (bulging
eyes) due to Graves
Disease.
• Goiter formation due to
inadequate iodine
consumption.
Posterior Pituitary
• Regulated through neural
stimulation from the hypothalamus.
• Produces 2 hormones in response to
nervous system stimulation.
– Antidiuretic hormone (ADH)
– Oxytocin
Thyroid Gland
• Located in the anterior
portion of the neck, just
below the throat.
• Releases hormones
that act on the
metabolic rate.
*T4: thyroxine
*T3: triiodothyronine
• Also produces the
calcitonin.
Parathyroid Gland
• Located on the posterior
surface of the Thyroid
gland.
• Secretes Parathyroid
Hormone (PTH)
– The MOST important
regulator of blood calcium
levels.
Adrenal Glands
• Located on the
superior aspect of
each kidney.
• 2 functional parts
*Cortex
*Medulla
Each part secretes a
specific type of
hormone.
Adrenal Gland Divisions
CORTEX
• Produces
hormones that
control fluid and
electrolyte
balance.
• Produces sex
hormones.
MEDULLA
• Produces
hormones for
sympathetic/
parasympathetic
nervous system.
Pancreas
• Located in
abdominal cavity
close to stomach.
• Produces hormones for the use
and storage of glucose
– Insulin
– Glucagon
Pineal Gland
• Pineal gland is
very close to the
optic nerve in the
brain.
• Produces
Melatonin that
activates sleepwake cycles.
Thymus Gland
• Located behind the
sternum.
• Decrease in size as
you age.
• Produces Thymosin
needed for the
production of Tlymphocytes.
T-cells are needed for
protection against
viral infections.
Ovaries and Testes
• Hormone producing glands (Gonads) of the
female and male reproductive systems.
• Controls fertility, reproduction, and gestation.
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Ovaries produce and
release estrogen and
progesterone
Testes produce
testosterone and
androgens
Other Hormone-Producing
Organs
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Placenta
Stomach
Intestines
Heart
Striated muscles
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Skin
Adipose/Fat
Liver
Kidneys
Uterus