Download Endocrine System Introduction

Chapter 9: Endocrine System
and Hormone Activity
Homeostatic Control through Hormone Release
Overview
•
•
•
•
•
•
ENDOCRINE = released into
the blood stream or interstitial
space.
EXOCRINE = released onto
epithelial surface.
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
Monoamine/Peptide
• Chemical base is
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.
• = 2nd Messenger
System
Classifications
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
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”
• Interacts closely
with the Nervous
System through the
hypothalamus.
• Protected by what
structure?
Sphenoid Bone
Anterior Pituitary Hormones
•
•
•
•
•
•
Growth Hormone (GH)
Prolactin (PRL)
Thyroid Stimulating Hormone (TSH)
Adrenocorticotropic Hormone (ACTH)
Follicle Stimulating Hormone (FSH)
Luteinizing Hormone (LH)
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
• Glucocorticoids
• Mineralcorticoids
– Control fluid and
electrolyte
balance.
• Androgens:
secondary sex
hormones.
MEDULLA
• Epinephrine/
norepinephrine
• Sympathetic and
parasympathetic
responses.
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.
• Melatonin:
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.
Testes produce testosterone
and androgens
Ovaries produce and release
estrogen and progesterone
Other Hormone-Producing
Organs
•
•
•
•
•
Placenta
Stomach
Intestines
Heart
Striated muscles
•
•
•
•
•
Skin
Adipose/Fat
Liver
Kidneys
Uterus