1. Unit 8: Endocrine System

2. Function Coordinates and directs the activity of the body’s cells
This is the same function of the nervous system
However:
Nervous system: signals are specific and fast-acting
Endocrine system: signals are wide-spread and long-lasting

3. Physiology: How does it work?
Hormones: chemical messengers that are released into the bloodstream and transported throughout the body
A given hormone only affects certain tissues or organs
Referred to as target cells or target organs

4. Lock and Key Model
Only certain hormones will affect certain organs because of the presence of the right receptor

5. Hormones 2 classes: Steroid hormones: comprised of fats
Nonsteroid hormones: comprised of proteins or amino acids

6. Steroid Hormones Hormones can pass straight through the cell membrane
Often derived from cholesterol
Lipid soluble
Let’s draw our own picture!

7. Nonsteroid Hormones
Hormones interact with the cell’s plasma membrane and initiate a cascade of signals that will occur within the cells
This is known as a second messenger system
Hormone = first messenger
Cascade of messengers and signals within the cell = second messenger
Let’s draw our own picture!

8. What do hormones control?
Reproduction
Growth and development
Mobilizing body’s defenses
Maintaining chemical homeostasis
Cellular metabolism and energy balance

9. How do hormones provide control?
Negative feedback
Hormones secretion inhibits further hormone release
Example: Ovaries release a hormone called estrogen.
When the ovaries release enough hormone to cause a slight increase in concentration in the blood, the ovaries stop secreting hormone
Let’s draw a picture of this!

10. Glands There are many major endocrine glands in the body Examples:
Hypothalamus
Pituitary
Thyroid
Parathyroid
Thymus
Adrenal gland
Pancreas
Ovary
Testis
Pineal Gland

11. WS #1 Endocrine Glands of the Body

12. Glands
The hypothalamus and pituitary glands are the head honchos of the endocrine system
In charge of controlling the release of all other hormones

13. Pituitary Gland Controlled by the hypothalamus Size of a grape
Sits on a bone called the sella turcica (Turkish saddle)
2 functional lobes
Anterior pituitary
Glandular tissue
Posterior pituitary
Nervous tissue

14. Pituitary Gland: Anterior Lobe
The anterior portion secretes hormones called tropic hormones
Stimulate target organs
Some are endocrine and some nonendocrine
All tropic hormones are
Nonsteroid hormones
Question: Where is the receptor located on the target cell?
On the plasma membrane!

15. Tropic Hormones

16. Let’s Make a Table! Hormone from Anterior Pituitary Abbreviation
Target Organ

17. Whiteboard practice!

18. Pituitary and Hypothalamus relationship
Anterior pituitary is controlled by the hypothalamus
The hypothalamus produces releasing and inhibiting hormones that control the release of the tropic hormones into the bloodstream

19. Hypothalamus Hormones
The releasing hormones are really easy to remember!
If the anterior pituitary is secreting growth hormone (GH), it was stimulated by growth hormone releasing hormone (GHRH) from the hypothalamus

20. Releasing Hormones
Predict: What tropic hormones will be secreted when the pituitary is stimulated with the following hormones?
Thyroid releasing hormone? (TRH)
TSH
Corticotropin-releasing hormone? (CRH)
ACTH
Gonadotropin-releasing hormone? (GnRH)
FSH/LH

21. Putting it all together with negative feedback
All of the hormones we have talked about exhibit negative feedback
Releasing hormone  tropic hormone  hormone
That is, the release of the target organ’s hormone will REPRESS the release of the hypothalamus and pituitary hormones

22. Let’s Draw a Picture!

23. Whiteboard practice!

24. Focus: Thyroid 1) hypothalamus secretes TRH
2) TRH stimulates the anterior pituitary to release TSH
3) TSH travels to target organ (thyroid)
4) Thyroid produces thyroid hormone

25. Thyroid Hormone
Function: Increase a person’s basal metabolic rate (BMR) (speed up their metabolism) and increase heat production
Question: If thyroid hormone exhibits negative feedback of further thyroid hormone production, excess thyroid hormone would cause ____________ and ___________ to stop being released.
TSH and TRH
This is negative feedback at work, folks!

26. Too Much? To Little?
Hyperthyroidism: excessive production of thyroid hormone
Causes Graves’ disease
Symptoms: constant feeling of warmth (as a result of increased BMR), weight loss, nervousness, and enlarged thyroid gland (goiter)
Hypothyroidism: decreased production of thyroid hormone
Symptoms: lower BMR (intolerance of cold), decreased appetite, weight gain

28. Focus: Adrenal Glands 1) hypothalamus releases CRH
2) CRH stimulates the anterior pituitary to release ACTH
3) ACTH travels to target organ (adrenal glands)
4) Adrenal glands produce cortisol

29. Question
If there is a high concentration of cortisol in the blood, the hypothalamus will release _______________ CRH.
A: more
B: less
CRH  ACTH  Cortisol

30. Cortisol
Function: promotes the breakdown of proteins and fats and helps the body adapt to stress
Provide the body with fuel to break down materials in the body
Can also act as an immunosuppressive and anti-inflammaory
Can shrink organs in the immune system
Ie thymus gland

31. Too Much? Too Little? Hypercortisolism: excessive amount of cortisol
Causes Cushing’s syndrome
Symptoms: personality changes, hypertension (high blood pressure), osteoporosis, and weight loss
Hyposecretion: decreased secretion of cortisol
Symptoms: defective metabolism, mental confusion, decreased ability to adapt to stress

32. Focus: Gonads 1) hypothalamus releases GnRH
2) GnRH stimulates the anterior pituitary to release LH
3) LH travels to the gonads (ovaries and testes)
3) Gonads secrete sex hormones (estrogen and testosterone)

33. Testosterone Function: Secondary sex characteristics of males
Increased body hair and deeper voice

34. Too Much? Too Little? Too much testosterone?
Increased muscle mass
Male pattern baldness
Acne
Premature sexual development
Decreased amount of testosterone?
Abnormal sexual development
Low sperm count

35. Rule of Thumb The more a gland is activated, the larger it gets
Known as hypertrophy (an increase in size)
Think about a person lifting weights—the more you use that muscle, the bigger your muscles get!
If a gland is continually inhibitied, it will shrink in size
Known as atrophy (shrinking in size)

36. Predict:
Let’s say your glands are 100% normal and they are working properly.
However, your target organs changed their “locks” AKA their receptors
Would they be responsive to hormones?
What would happen if a person with an XY chromosome was born with an insensitivity to testosterone?

37. Androgen Insensitivity Syndrome
The receptors on the target cells for testosterone (for example, the ones in the gonads) are unresponsive to testosterone
This would have occurred since birth—this is a congenital disease
The female set-up is default
Without testosterone, you would end up looking like a female on the outside
These individuals spend their whole lives thinking that (and looking like) they are female until puberty
They would grow the secondary sex characteristics (breasts), but menstruation would not occur
This is usually the time when they diagnose this disease