The Neuroendocrine System

This CrashCourse video is a little long but I encourage you to watch it!

Puberty

This period is associated with an increase of hormones released by the anterior pituitary

• growth hormone- produces the growth spurt by acting on bones and muscle
• ACTH- causes the gonads and adrenal cortex to release hormones that leads to maturation of the genitals and secondary sex characteristics

• Males have higher androgen levels than estrogen levels
• Females have higher estrogen levels than androgen levels
• The results of these hormone levels are masculinization and feminization in terms of normal sexual maturation

• Remember: don't refer to androgens as "male hormones" or estrogens as "female hormones"

External Reproductive Organs

Male and female genitals develop from a bipotential precursor:

Sexual Development of the Body

• the glans
• males- head of the penis
• females- clitoris
• urethral folds
• males- they fuse
• females- labia minora
• lateral bodies
• males- shaft of the penis
• females- hood of the clitoris
• labioscrotal swellings
• males- scrotum
• females- labia majora

References

Pinel, J. (2014). Biopsychology.

• 6 weeks after fertilization, each fetus has the same gonadal structures: a cortex with potential to develop into an ovary and a medulla with potential to develop into a testis
• in males, the medulla develops into a testis after the Sry protein is synthesized by the Sry gene on the Y chromosome
• since females do not have an equivalent of this protein, the cells of their gonads develop into ovaries

http://www.endocrineweb.com/endocrinology/overview-pituitary-gland

http://arbl.cvmbs.colostate.edu/hbooks/pathphys/endocrine/hypopit/overview.html

• In males, the testes secrete testosterone and Müllerian-inhibiting substance
• Testosterone stimulates Wolffian system development while Müllerian-inhibiting substance causes degeneration of the Müllerian system
• Female reproductive ducts develop in any fetus not exposed to testicular hormones during the critical period

Internal Reproductive Ducts

Both males and females have these two sets of reproductive ducts:

• Male Wolffian system and female Müllerian system

The Pituitary Gland

The presence or absence of testosterone controls the development of these ducts.

Warning about mamawawa!

• pea-sized gland located in the base of the brain near the hypothalamus
• consists of 2 lobes/glands:
• posterior pituitary- main hormones are oxytocin (stimulates contractions of uterus during childbirth and stimulates breast milk production) and vasopressin (facilitates reabsorption of water by the kidneys)
• anterior pituitary- releases tropic hormones, which influence release of hormones from other glands

Control of the Pituitary

We shouldn't think of sex hormones as "male" or "female" because testes and ovaries release the same hormones (in different quantities)

• The pituitary's neural input from the hypothalamus all goes to the posterior pituitary
• The anterior pituitary has no neural connections with the hypothalamus
• The hypothalamus synthesizes oxytocin and vasopressin and uses the hypothalamopituitary portal system to carry hormones to the anterior pituitary
• Releasing hormones (from the hypothalamus) stimulate release of anterior pituitary hormones.

Gonads and Sex Steroids

Gonads- the male testes and female ovaries

Besides sperm and egg cells, the gonads also make hormones:

1. androgens- the most common one is testosterone

2. estrogens- the most common one is estradiol

3. progestins- the most common one is progesterone

Glands and Hormones

2 types of glands:

• exocrine- release their chemicals into ducts, which carry them to their targets on the surface of the body
• endocrine- release their chemicals, hormones, directly into the circulatory system

3 classes of hormones:

• amino acid derivatives
• peptides and proteins
• steroids

What is the mamawawa and what's wrong with it?

mamawawa = Men are men and women are women assumption

"...the tendency to think about femaleness and maleness as discrete, mutually exclusive, opposite categories." (Pinel, 2014)

This assumption leads us to think of sex differences as being fixed, when in reality there can be a lot of overlap between maleness and femaleness.

Neuroendocrine System and Puberty

Patricia Madrid