1. Hormones & the Endocrine System

2. I. The Effects of Prenatal Hormones on Sexual Development
XX & XY – first 6 weeks of life all embryos are female
1. Primordial gonads
a. Mullerian system – Female, destined to form female internal organs & female external genitalia
b. Wolffian system – Male equivalent, destined to form male internal organs & male external genitalia

4. 2. By 12 weeks after conception a process of masculinization is occurs
1. All children are born with both, there is an active process that allows Wolffian system to take over and make males.
2. By 12 weeks after conception a process of masculinization is occurs
i. Synthesis of H-Y antigen (about 6 weeks) leads to the synthesis of testosterone, which activates the Wolffian system & Mullierian Inhibiting Substance
which blocks further development of the female system
**Maternal estrogen does not cross the blood-placental barrier**
**Testosterone can cross the blood-placental barrier**

5. In the body of the of the developing fetus:
Testosterone: Responsible for masculinizing male genitalia (testosterone binds to androgen receptor
for masculine genitalia)
Female disorders (too much testosterone)
1. For triplets with 1 female and 2 males the female will have enlarged external genitalia

6. 2. Adrenal congenital hyperplasia –. There is a balance between
2. Adrenal congenital hyperplasia – There is a balance between testosterone & corticosteroids, in this disorder there is too little corticosteroids which results in increased testosterone
i. Testosterone crosses blood – placental barrier and masculinizes female genitalia in female fetus’s, “intersexed appearance”
ii. Testosterone is undergoing aromatization to masculinize the brain

7. An interesting wrinkle based on animal research:
Aromatization hypothesis – for masculinizing the brain (testosterone  estradiol): see diagram

8. Aromatization of Testosterone

9. Male disorders (too little or ineffective testosterone) – androgenic insensitivity
1. XY: X chromosome is responsible for the testosterone receptors
i. These receptors become insensitive to testosterone
ii. Child is born with appearance of female genitalia
**Mullerian inhibiting system is okay; so internal organs are not female**

10. II. Endocrine System vs Neuronal System
1. Neural & Hormonal communication
a. Similarities
i. Chemicals are stored and released
ii. Release of chemicals is due to stimulation
iii. Many different hormones & neurotransmitters
iv. Both systems react w/specific receptors

11. v. Second messenger involved in both
(The first messenger reacts to the initial signal - like an ionotropic
receptor, found in CNS only)
2. Second messenger reacts to a signal from a first messenger (like a
metabotropic receptor) and affects
intracellular functioning; it is a
complex intracellular response that
affects functioning.

12. Hormones are Extremely Powerful

13. b. Differences
i. In nervous system, neurons communicate with adjacent neurons; in hormones messages are sent long distances
ii. Neural messages induce rapid response compared to hormones which have slower messages
iii. Neural messages follow the all or none principle; hormonal messages are graded in strength
iv. Neural messages can be directed as observed in behavior; hormonal messages are primarily involuntary (cannot be directed)

14. 2. Three types of hormones
a. Protein hormones – effect is on receptors within the membrane, binds to the receptors on the outside of membrane; its effects are the most rapid of all the hormones
i. Oxytocin – involved in development of relationships
ii. Adrenocorticotrophin – protein hormone; chains of amino acids

15. 1. Estrogen, progesterone, androgens ii. Adrenal hormones
b. Amine hormones – same relatively fast receptor response as protein hormones
i. Epinepherine
ii. Norepinepherine
iii. Thyroid hormones
iv. Melatonin
c. Steroid hormones – binds to the intercellular receptors; slow actions
i. Gonadal hormones
1. Estrogen, progesterone, androgens
ii. Adrenal hormones
1. Glucocorticoids, mineralocorticoids

16. Major Glands of the Endocrine System
Hypothalamus
Pituitary
Thyroid
Adrenal
Gonads: Ovaries & Testes

17. Six Highlighted Endocrine Glands

19. Pituitary Anterior Pituitary
- derived during embryological development from the roof of the mouth
- connected to the hypothalamus by a portal system (hypothalamic-pituitary portal system)
- most of the hormones are released from the anterior pituitary

20. Posterior Pituitary
- derived from nervous tissue
- two protein hormones released: oxytocin & vasopressin
_________________________________
Two Important Points:
Hormones released from the posterior pituitary are synthesized in the hypothalamus.
Hormones released from the anterior pituitary are dormant unless directed to be released by the hypothalamus via Releasing Factors.

23. Pituitary & all Hormones are Under the Control of the HypothalamusRF
Hormone
Anterior Pituitary
Posterior Pituitary
Hormone SH
Target Organs
Target Organs
RF = Releasing Factor SH = Stimulating Hormone

25. Hypothalamic Hormones:
Gondotropin RF
Corticotropin RF
(CRF)
Thyrotropin RF
Growth Hor RF
Prolactin RF
Pituitary Hormones:
Growth
Hormone
Prolactin
Adrenocorticoptropin
Hormone (ACTH)
Thyrotropin SH
Follicle SH &
Lutenizing Hor.
Target Gland or Structure:
Bones, breasts & cells of body
Cells of body
Ovaries & Testes
(androgens, estrogen)
Adrenal Gland
(cortisol)
Thyroid Gland
(thyroxine)

26. Adrenal Gland
i. Adrenal cortex (outer) produces about 50 different chemicals including…
1. Mineralocorticoids (outer layer)
2. Glucocorticoids, cortisol (middle layer)
3. Sex hormones (inner most layer)
a. Estrogen, progesterone androgens
note: Congenital adrenal hyperplasia – too much testosterone produced by mother. This comes from dysfunction in adrenal gland.
ii. Adrenal medulla (inner)
1. Dopamine  Norepinepherine/Epinepherine

27. Thyroid Gland 1. Too little thyroxin – hypothyroidism
a. Depression (clinical or subclinical), attention & memory problems
2. Too much thyroxin – hyperthyroidism
a. Agitation, irritability, & weight loss
*Goiters – Growths on thyroid gland

28. Gonads & Hormones
LH & FSH

29. Growth Hormone Cells of body in response to growth hormone
i. During childhood GH is at maximum
1. Too little and we have a small person
2. Too much and we have gigantism, often accompanied by acromegaly (continued growth of extremities of bones)
a. Makes hands, feet, jaw, nose, and eye sockets (orbits) enlarged

30. Oxytocin The hormone involved in inducing labor during childbirth
Hormone involved in bonding
Hormone involved in relationships
Might be deficient in Autism

31. All hormones utilize feedback loops:
Autocrine response – Same as the autoreceptors, both communicate and terminate release
Note similarity to the CNS:
Autoreceptors – in the CNS the receptors on presynaptic cell that are sensitive to its own NT

32. Feedback Mechanisms

33. Hormones are Extremely Powerful

34. Ultimately,what controls the endocrine system?
Higher Brain Areas
Hypothalamus
Pituitary
Endocrine Glands
Our emotions
Our perceptions
Our cognitions
Our experiences
Our behavior
Our response to
the environment