1. Homeostasis and the Endocrine System

2. Endocrine System
Endocrine system: consists of ductless glands that release hormones into the blood
Hormones~ chemical signals that are transported in blood (communicates regulatory messages) (Option H)
Target cells~ body cells that respond to specific hormone (Option H)
Feedback mechanisms
Essential idea: Hormones are used when signals need to be widely distributed.

3. Homeostasis and Negative Feedback
Homeostasis = maintaining the internal environment of the body within limits (a steady state).
Negative feedback maintains homeostasis
Level of the hormone has an effect that controls the hormone’s secretion
Ex. If ADH levels are high, secretion of ADH slows.
If ADH levels are low, secretion of ADH increases.

4. The Hypothalamus Brain Region that links nervous and endocrine system.
Controls the pituitary gland (the body’s “master gland”

5. Hormone Examples: Insulin and Glucagon
Islets of Langerhans– clusters of endocrine cells in pancreas
Alpha (α) cells: •glucagon~ raises blood glucose levels
Beta (β) cells: •insulin~ lowers blood glucose levels
Negative feedback!.

6. Diabetes mellitus Two types:
Blood glucose homeostasis is NOT effectively maintained in diabetes
How the disease was named:
Greek diabainein (to pass through), refers to excessive urination of diabetics.
Latin mellitus (honey-sweet)
Two types:

7. Type I diabetes mellitus
Onset: childhood
autoimmune disorder (immune system destroys beta cells)
insulin-dependent (Beta cells produce insufficient insulin)
Insulin injections required

8. Type II diabetes mellitus
Type II diabetes mellitus
Onset: later in life (usually after childhood
non-insulin-dependent
reduced responsiveness to insulin (insensitivity)
Can usually be controlled with low carb diets (insulin injections usually not needed)

9. Thyroid Gland
Thyroxin is secreted by the thyroid gland to regulate the metabolic rate and help control body temperature.

10. Leptin is secreted by cells in adipose tissue and acts on the hypothalamus of the brain to inhibit appetite.

11. Application: Testing of leptin on patients with clinical obesity and reasons for the failure to control the disease.
Most cases of obesity are caused by an unresponsiveness to leptin and not a leptin deficiency 
An obese and healthy mouse are given leptin in both of these experiments, but the end result is different. Why?

12. Pineal Gland and Melatonin
Melatonin is secreted by the pineal gland to control circadian rhythms.
Application: Causes of jet lag and use of melatonin to alleviate it.

13. Utilization: • Hormones are used in a variety of therapies such as replacement therapies.
Aim 8: Scientists are aware that the drugs women take in fertility treatment pose potential risks to health. Should scientific knowledge override compassionate considerations in treating infertile couples?

14. Sex hormones
Discussed in reproduction system ppt.

15. End of IB

16. Vertebrate Endocrine System
Tropic hormones ~ a hormone that has another endocrine gland as a target
Hypothalamus~pituitary
Pituitary gland
Pineal gland
Thyroid gland
Parathyroid glands
Thymus
Adrenal glands
Pancreas
Gonads (ovary, testis)

17. The Anterior Pituitary
Anterior pituitary hormones:
Growth (GH)~bones √gigantism/dwarfism
√acromegaly (abnormal growth of bones in head, hands, feet in adults)
Prolactin (PRL)~mammary glands; milk production
Follicle-stimulating (FSH) & Luteinizing (LH)~ gonadotropins (affect ovaries/testes)
Thyroid-stimulating (TSH)~ stimulates thyroid gland
Adrenocorticotropic (ACTH)~ stimulates adrenal cortex to secrete hormones
Melanocyte-stimulating (MSH)– regulates pigmented cells, fat metabolism
Endorphins~natural ‘opiates’; brain pain receptors

18. The posterior pituitary
Oxytocin~ uterine muscle contraction during childbirth and mammary gland milk secretion
Antidiuretic (ADH)~ retention of water by kidneys

19. The pineal, thyroid, & parathyroid glands
Melatonin~ pineal gland; biological rhythms
Thyroid hormones: Calcitonin~ lowers blood calcium (opposite effects of PTH—see below
Thyroxine~ regulates metabolic processes (speeds up metabolism)
Parathyroid hormone (PTH)~ raises blood calcium (reabsorption in kidneys, release of calcium from bone)

20. The adrenal glands
Adrenal medulla (catecholamines): •epinephrine & norepinephrine~ increase basal metabolic rate (blood glucose and pressure)
Adrenal cortex (corticosteroids): •glucocorticoids (cortisol)~ raise blood glucose
•mineralocorticoids (aldosterone)~ reabsorption of Na+ and K+, and water

21. The gonads Steroid hormones: precursor is cholesterol
androgens (testosterone)~ sperm formation; male secondary sex characteristics; gonadotropin
estrogens (estradiol)~uterine lining growth; female secondary sex characteristics; gonadotropin
progestins (progesterone)~uterine lining growth and maintenance

22. Local regulators: cells adjacent to or near point of secretion
Growth factors ~ proteins for cell proliferation
Nitric oxide (NO) ~ neurotransmitter; cell destruction; vessel dilation
Prostaglandins ~ modified fatty acids secreted by placenta and immune system; cause uterine contractions during labor, induce inflammation