1. Chapter 9: The endocrine system
Bio 24
what is the endocrine system?

2. The endocrine system One of two communication systems in the body
Consists of hormones: chemicals secreted into the blood that travel throughout the body to act on specific target cells
Only cells with the appropriate receptors will respond to the hormonal signal

3. Functions of the endocrine system
Hormones are essential for:
reproduction
regulation of the immune system
utilization of energy
maintenance of bone and muscle mass
growth
regulation of salt and water balance and blood pressure
regulation of our moods & emotions
many other things!

4. The endocrine vs. the nervous system
Endocrine system
uses chemical signals
chemical signals secreted into the blood
effects take minutes or hours and may be long-lasting
Nervous system
uses chemical and electrical signals
chemical signals travel only across a synapse
effects take a fraction of a second and usually mediates rapid responses

5. 2 main categories of hormones
Amino acid-based hormones (most common) include proteins, peptides, and amino acid derivatives
Include insulin, growth hormone, thyroid hormones
Steroid hormones are small lipid molecules made from cholesterol that can cross cell membranes
Include testosterone, estrogen, progesterone, and cortisol

6. Steroid hormone action

7. Nonsteroid hormone action uses second messengers in the cell

8. Control of hormone release
Release of most hormones is controlled by other hormones
Hormones that control the release of other hormones are called tropic hormones

9. Control of hormone release
Some hormones are released in response to humoral stimuli: substances in the blood that are not hormones

10. Control of hormone release
Release of some hormones is controlled by the nervous system
The nervous and endocrine systems often work together in a coordinated fashion

11. the major endocrine organs

12. Endocrine organs
Most hormones are released from epithelial cells that form endocrine glands
Major ones are shown here

13. The hypothalamus is the master controller through the pituitary glands
Tropic hormones from H control hormone release from pituitary gland

14. Hormones of the anterior pituitary: growth hormone
Growth hormone promotes growth of bones and muscles in children, and maintenance of muscle mass in adults
Growth hormone excess can result in gigantism (if in childhood) or acromegaly (if in adulthood)

15. Hormones of the anterior pituitary: prolactin
Stimulates and maintains milk production
Men make it, too, but function is unknown!

16. Hormones of the anterior pituitary: adrenocorticotropic hormone (ACTH)
ACTH is a tropic hormone that regulates the activity of part of the adrenal glands called the adrenal cortex
Glucocorticoids released from the adrenal cortex increase blood glucose and are involved in our stress response; mineralocorticoids regulate salt and water balance by controlling urine composition

17. Hormones of the anterior pituitary: follicle-stimulating hormone (FSH) and luteinizing hormone (LH)
Both these hormones control the hormonal activity of the gonads: testes and ovaries
Both are essential for the development of both sperm and eggs

18. Hormones of the anterior pituitary: Thyroid-stimulating hormone (TSH)
TSH influences the growth of and hormone release from the thyroid gland
The thyroid gland releases thyroid hormones, which contain amino acid-like molecules bound to iodine atoms and also calcitonin, which regulates calcium deposition in bones

19. Structure of the thyroid
colloid is what thyroid hormones are made of

20. Thyroid hormone targets
Thyroid hormones act on essentially every cell in the body
Control metabolic rate and energy utilization
Also important for normal growth and development and reproductive function
Thyroid disease is quite common!

21. Thyroid deficiency
Hypothyroidism (underactive thyroid) is most often caused by autoimmune disease that attacks the thyroid
Symptoms include fatigue, persistent feeling of cold, bloating and weight gain, dry skin, and mental slowness
Can be very well treated by taking thyroid hormone pills
Thyroid deficiency in children can cause mental retardation and dwarfism, known as cretinism

22. Thyroid excess
Hyperthyroidism (overactive thyroid) can also result from autoimmune disease or a benign tumor of the thyroid
Graves’ disease is one form of hyperthyroidism that also causes exophthalmos (bulging eyes)
Symptoms include rapid heart rate, heat intolerance, and nervous behavior
Hyperthyroidism is harder to treat

23. Goiter A goiter is an enlarged thyroid
Can be caused by hyperthyroidism or hypothyroidism
Traditionally caused by dietary iodine deficiency