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/2006/06/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/webnotes/Image15.gif

Adenohypophysis ( Anterior)

• Not part of the nervous system!• Releases many tropic hormones1.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 continued3. Growth Hormone- stimulates growth

and metabolic regulation4. Prolactive- Milk production5. 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/endocrine/library/images/graph/negative_feedback.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 Triiodothyronine- stimulates 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/diabetes-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