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The Endocrine System
Chapter 46
Hormones
• Chemical Messengers
• Released by “endocrine glands”
– Some organs release hormones as well
• The liver
• The Kidney
– Some Neurons release Neurohormones
• Pheremones are also hormones
Regulation of Hormones
• Most regulated by the Nervous system
• Some exceptions
– Insulin from the pancreas
– Aldosterone from the Adrenal Cortex
Types of Chemical
Messengers
• Endocrine
– Hormones relased into blood
• Paracrine
– Released within organ
• GFs
• NO
• Prostaglandins
– Muscle Contraction
– Inflamation
» Aspirin- cox1 vs cox 2
• Neural
• Special case- Exocrine
Classes of Chemical
Hormones
• Peptides and Proteins- made of AA’s
– ADH, Insulin, GH
• Amino Acid Derivatives-made by
modification of specific AA’s
– Biogenic amines
• Steriods- lipids made by mofication of
cholesterol
– Testosterone, estradiol, progesterone etc
Lipophilic vs Hydrophilic
• Lipophilic- nonpolar and fat soluble
– Steriod and thyroid hormones
– Can enter the cells and activate intracellular
receptors because of their solubility
– Take longer to work, but effects last longer
• Hydrophilic- polar and water soluble
– Cannot enter cells directly
– Bind to the outside and use G protein activity to
activate RTK cascades
– Act quickly, but results short lived
Hydrophilic often use
Secondary Messengers
• Ex cAMP activated by Gprotein, which then in
turn activates an RTK cascade.
• Can be Activators or Inhibitors based on the
receptor cell- also has different effects on
different cells
– Epinephrine in Liver- activates and promotes the
production of Glucose
– Epinephine in muscles- IP3 regulated calcium
release causing muscle contraction.
Parts of the Endocrine System
• http://scienceblogs.com/clock/upload/20
06/06/endocrine%20system.jpg
Pituitary- Street Name
Hypophysis
• Anterior Pituitary aka Adenohypophysis
• Posterior Pituitary aka Neruophpophsis
Neurophpophysis (Posterior)
• Contains axons that originate in the
hypothalamus
• Antidiuretic Hormone- Stimulates water
reabsorption by the kidneys
• Oxytocin- stimulates milk ejection and uterus
contraction
• Actually Neruoendocrine because hormones
are made in the hypothalamus and stured in
the PP.
• http://www.mrothery.co.uk/module4/web
notes/Image15.gif
Adenohypophysis ( Anterior)
• Not part of the nervous system!
• Releases many tropic hormones
1.Adrenocorticotropic Hormone(ACTH) stimulate the adrenal cortex to produce
cortisol- regulates glucose
2.Melanocyte Stimulating Hormone
(MSH)- stimulates the dispersion of
melanin pigment
AP hormones continued
3. Growth Hormone- stimulates growth
and metabolic regulation
4. Prolactive- Milk production
5. Thyroid-stimulating hormone(TSH)stimulates release of thyroxine which
regulates development and metabolism
6. Luteinizing hormone(LH) stimulates
production of estrogen and
progesterone in the ovaries, as well as
testosterone in the testis.
AP Hormones Continued
7. Follicle-stimulating hormone (FSH)Required for development of ovarian
follicles in females, and sperm in males
-FSH and LH are gonadotropins
Hypothalmic Neurohomes
regulate the Anterior Pituitary
• Releasers- signal the release of
different hormones from the
adenohypophesis ex TRH
• Inhibitors- Inhibits the release of
adenohypophesis hormones ex GHIH
• Why doesn’t the neurohypophysis need
to be regulated by hormones from the
Hypothalamus?
Negative Feedback and the
Hypothalamus
• http://ec.europa.eu/environment/endocri
ne/library/images/graph/negative_feedb
ack.gif
Iodine Deficiency Blocks
Negative Feedback
• Without Iodine thyroxine cant be made.
• No inhibition of hypothalamus
• Hypothalamus keeps signaling
adenohypophysis to makes TSH
• Thyroid keeps trying but cant
• Goiter Develops
Positive Feedback and the
Hypothalamus
• Ovulation
– Increased Estrogen
– Surge of LH
– Egg Released
– Stops when the ovarian follicle is destroyed
by the LH surge
Thyroid Gland
• Thyroxine and Triiodothyroninestimulates metabolic rate and essential
to normal growth and development
– Constant in humans cycles in reptiles
amphibians and fish
• Higher during times of metamorphisis
• Calcitonin-maintains proper levels of
Calcium
Parathyroid
• Behind the thyroid
• Releases Parathyriod Hormone(PTH)stimulates dissolution of bone and
reabsorption of Calcium by the kidneys.
Indirectly stimulates intestinal
absorbtion of Calcium by activating
Vitamin D
• Why do we need vitamin D?
Regulation of Blood Calcium
Adrenal Glands
• Located abone each kidney
• Inner portion is the Adrenal Medulla
• Outer Potrion is the Adrenal Cortex
Adrenal Medulla
• Receives Nerual Input from the
Sympathetic Nervous System
• Along with the Autonomic Nervous
system will release epinephrine and
norepinephine
Adrenal Cortex
• Corticosteroids ex cortisol- maintains glucose
homeostasis
– Regulated by the anterior pituitary
• Glucocorticoids- stimulate breakdown of muscle protein
into AA’s. Stimulates liver to release enzymes needed to
convert AA’s into glucose
– Also play a role in immune respones
• Aldosterone- regulates mineral balance- stimulates
didneys to absorb excess Na+ maintains K+ Na+
balance.
Pancreatic Hormones
• Insulin-Lowers blood glucose levels,
stimulates glycogen, fat, and protein
synthesis
• Glucagon- raises blood glucose levels,
stimulates the breakdown of glycogen in
the liver
– Both produced by the islets of Langerhans
• http://www.geneticsrus.org/DNA/diabete
s-glucose-regulation.gif
Sex Steriods
• Ovaries
– Estradoil- development of female sex
characteristics
– Progesterone-preparation for pregnancy as
well as milk production
• Testis
– Testosterone- secondary male sex
characteristis and spermatogenesis
Pineal Gland
• Melatonin- regulates biological rythms
Insect Hormones
• Prothoracicotropic Hormone stimulates
molting hormone ecdysone.
– High levels of Ecdysone cause molting
• Juvenile Hormone- high levels prevent
metamorphsis