1. Integration and Control:
THE ENDOCRINE SYSTEM
Campbell & Reece Chapter 45

2. Endocrine
Hormones: substances produced by particular tissues of the body carried by the bloodstream to "target cells," upon which they exert special effects
*Hormones are secreted by glands, made mostly of epithelial tissue
Exocrine glands: secrete into ducts (sweat glands, digestive glands)
Endocrine glands: secrete hormones (into bloodstream) "ductless glands"
Endocrine Gland--->hormone--> Bloodstream------> target organ/tissue

3. Active in very small quantities Controlled by:
Hormones may be:
Steroids
Peptides/proteins;
Amino acids
Active in very small quantities
Controlled by:
Negative Feedback
Rapid degradation by the body
Hormonal communication

4. Positive & Negative feedback

5. Mechanisms of Action of Hormones:
2 Main ways that Hormones Effect Target Cells:
Intracellular receptor molecules- steroids, thyroid hormones
Membrane receptor molecules- amino, peptide, protein hormones
A.  Intracellular Receptors
Steroid hormones and thyroid hormones are soluble in lipids and pass freely through cell membranes; must contact receptor site with in a cell
This changes a cell’s actions (protein synthesis, etc.)
B.  Membrane Receptors
Combine with receptors on or in the membrane target cells
Once combined, send a second messenger inside ? to the nucleus (cyclic AMP)
May simply increase/decrease a cell’s permeability to substances
Action of Steroid Hormones

6. The Hypothalamus-Pituitary Axis:
Pituitary was once considered the "master gland" until it was learned that it was under control of the hypothalamus (brain region)
The hypothalamus makes several hormones which travel to and are released by the pituitary lobes.
Target tissues are stimulated by (or inhibited by) release of these hormones into the bloodstream.

7. Hormone
Major Target Organ(s)
Effects
Anterior Pituitary
Growth hormone (GH)
Liver, adipose tissue
Promotes growth (indirectly), control of protein, lipid and carbohydrate metabolism
Thyroid-stimulating hormone (TSH)
Thyroid gland
Stimulates secretion of thyroid hormones
Adrenocorticotropic hormone (ACTH)
Adrenal gland (cortex)
Stimulates secretion of glucocorticoids
Prolactin (PRL)
Mammary gland
Milk production
Luteinizing hormone (LH)
Ovary and testis
Control of reproductive function
Follicle-stimulating hormone (FSH)
Posterior Pituitary
Antidiuretic hormone (ADH)
Kidney
Conservation of body water
Oxytocin
Stimulates milk ejection and uterine contractions

8. The Hypothalamus-Pituitary Axis:
About the size of a kidney bean
Divided into three lobes: Anterior, posterior, intermediate

9. Anterior Pituitary
Somatotropin = growth hormone (GH), stimulates protein synthesis, growth of muscle and bone
Deficit: midget
Excess: giantism (acromegaly)
Affects glucose metabolism; inhibits uptake and oxidation of glucose by cells, stimulates breakdown of fatty acid for energy (conserves glucose)
Prolaction (PRL) –stimulates the secretion of milk in mammals
controlled by inhibiting hormone in hypothalamus
continued by nerve impulses from suckling; hypothalamus (supply upon demand)

10. Intermediate Pituitary Lobe
Melanocyte- stimulating Hormone (MSH)
(Wikipedia)  ...stimulate the production and release of melanin (melanogenesis) by melanocytes in skin and hair.
MSH is also produced by a subpopulation of neurons in the hypothalamus.
MSH released into the brain by these neurons has effects on appetite and sexual arousal.
More important for color change in reptiles, etc.

11. Posterior Pituitary Lobe
Hypothalamus releases Oxytocin and antidiuretic hormone (ADH) and stores it here, released by posterior pituitary
Oxytocin- "milk let down" hormone, stimulates uterine contractions, smooth muscle contraction (BP regulation)
Antidiuretic Hormone (ADH)- a.k.a. vasopression (increase BP) decreases excretion of water by kidneys. Increases permeability of water in nephrons

12. Regulation of The Other Glands:
Regulation: negative feedback system involving a gonadotropic (gonad-stimulating) hormone
LH (luteinizing hormone): produced by ant. pituitary
In males:
LH is carried by blood to stimulate testes
as blood level of testosterone increases, LH production decreases
In females:
rise in LH stimulates ovulation
FSH (follicle-stimulating hormone):
In males: acts upon the sertoli cells of the testes, important for spermatogenesis
In females:  stimulates maturation of germ cells, sets mentrual cycle
High concentrations of LH cause germ cells to produce an inhibitor, "inhibin", which will then lower LH levels

13. The Endocrine Glands

14. Testes Androgens- the "male sex hormones"
Testosterone (steroid) is one type.  Produced in the testes necessary for sperm production and secondary sex characteristics:
genitals
larnyx (voice change)
skeletal enlargement
muscle tissue
acne

15. The Ovaries Estrogens- the "female sex hormones"
Different kinds of estrogen hormones:  estriol, estrone, and estradiol (most important)
Produced by ovaries by stimulation of FSH from pituitary
Stimulate development of secondary sex characteristics (breast development, genital development, distribution of body fat)
Progesterone- maintenance of pregnancy, uterus
(estrogen, progesterone interaction= menstrual cycle)
estrus cycle diagram, showing hormone fluctuations in the mare

16. Prostaglandins Hormone-like chemicals differ from other hormones:
Fatty acids (formed by oxygenation of Arachidonic Acid)
Produced by cell membranes of most organs (as opposed to specific glands)
Often exert effects on the tissues that produce them
The target tissue may be that of another person (e.g. in semen, for fertilization)
More patent than hormones (needed in smaller amounts)
Effects- stimulation of smooth muscle (uterus- menstruation labor); blood vessel dilation/constriction (BP down, up); inflammatory response by T-cells

17. Adrenal Glands
Adrenal Cortex- outer layer of adrenal glands; major source of steroid hormones
Adrenal glands lie on top of kidneys ("ad-renal")
Humans: two major groups of adrenocortical steroids
Glucocorticoids
Mineralocorticoids

18. Adrenal Cortex: Glucocorticoids
Glucocorticoids- used to suppress inflammation (medical)
Cortisol- (most important) mainly the formation of glucose from fats and proteins. Inhibit up take of glucose by most cells (except brain and heart). Release increases during excitement etc.; work with sympathetic nervous system.
Secreted in response to Adrenocorticotropic Hormone (ACTH), secreted by Ant. Pituitary ("master gland") which is stimulated by hormone released from Hypothalamus

19. Adrenal Cortex: Mineralocorticoids
Affect the ion concentration in the blood; water loss/retention.
Aldosterone- (example) regulation of ions (K+, Na+)
Affect the transport of ions across membranes of the NEPHRONS
Deficiency leads to Na+ ion loss (via urine) = loss of water = lowers blood pressure
Since adrenal cortex is source of androgens (male and female) sex hormones, a tumor can increases male secondary sex characteristics (e.g. bearded ladies)

20. Adrenal Medulla
Central portion of adrenal made up of neurosecretory cells (rather than epithelial)
Adrenaline and Noradrenalin- increase rate and strength of heartbeat; raise BP; dilate resp. passages (act as enforcer of sympathetic N.S.)

21. Pancreatic Hormones: "Islets of Langerhans"
Insulin: secreted in response to rise in blood sugar or AA concentration. It lowers blood sugar by stimulating up take of glucose (conversion of glucose to glycogen by liver)
Glucagon: increases blood sugar by breakdown of glycogen glucose in liver and breakdown of fats/proteins
Somatostatin: synthesis of insulin
Five different sugar-regulating hormones (growth hormone, cortisol, insulin, adrenalin, glucagon)
Diabetes- insulin too low
Hypoglycemia- insulin too high

22. Thyroid Gland: Located on top of Larynx
Controlled by "hypothalamus- pituitary axis" - TSH (thyroid-stimulating hormones a.k.a. "thyrotropin"
A.  Thyroxine
Accelerates rate of cellular respiration (metabolism)
differs from androgens, estrogens, corticosteroids because it is an amino acid with 4 iodine atoms (T4), also T3
B.  Calcitonin: inhibits release of calcium ions [Ca2+ ions] from bones. Secretion is controlled by Ca ion conc. in fluid around thyroid cells.

23. Thyroid diseases
Goiter is a swelling of the thyroid gland, results from low iodine in diet
Hyperthyroidism: (overproduction) weight loss, nervousness, fatigue.  Most common cause in Grave's Disease.
Hypothyroidism: (underproduction) dwarfism in infants (Cretinism) low energy, low brain cell development, can be caused by insufficient iodine in diet
autoimmune disease of thyroid :  Hashimoto's thyroiditis

24. Parathyroid Glands:
Located below thyroid, pea- size, smallest endocrine gland
Parathormone: essential in mineral metabolism, regulation of Calcium and Phosphate ions in blood
stimulates release of Ca?? ions from bones; secreted in response to low blood [Ca2+]
(Calcium = blood coagulation, muscle contraction, nerve function)

25. The Pineal Gland Small lobe in forebrain, near center
Involved in "photoperiodism"- seasonal enlargement of ovaries etc.
Secretes hormone: Melatonin (up/down, day/night)
Melatonin: causes pigment cells to open/close "biological clock"