Ch 13

Exocrine

Release chemicals into ducts which carry them to their targets. Ex: Sweat Glands, Salivary glands, etc

Endocrine

Ductless. Release hormones directly into the circulatory system

Organs whose primary function is to release hormones.

Three main types of hormones

1. Amino acid derivatives-Epinephrine, for example (from the adrenal gland)

2. Peptides and proteins- Short and long chains of amino acids. Both amino acid derivatives and peptides/proteins bind to receptors at cell membranes.

• Many of these hormones also function as neurotransmitters also. Neuropeptides – oxytocin

3. Steroid Hormones-Synthesized from cholesterol (i.e., fat) Bind to receptors at cell membrane AND inside cell.

• Steroid Hormones Can have diverse and long-lasting effects on cells. Play a major role in sexual development and behavior.

List the Endocrine glands(10)

Exist in number of locations in body including brain. Hypothalamus, Pituitary gland, and Gonads(Testes or Ovaries) are important for sexual development and behavior

pineal gland

Hypothalamus

Pituitary Gland

Thyroid

Parathyroid

Thymus

Adrenal gland

Pancreas

Ovary(In females)

Testis(In Males)

Gonads

Produce and release special steroid hormones called sex hormones:

Androgens - e.g., testosterone

Estrogens - e.g., estradiol

Progestins – e.g., progesterone

• Both testes and ovaries secrete all 3 of these hormones

In sexual development Both sexes begin with both sets of reproductive ducts called

Wolffian system Male – seminal vesicles, vas deferens. Mullerian system- Female – uterus, vagina, fallopian tubes

• Testes produce testosterone and Anti-Mullerian-Hormone Wolffian system develops (from T). Mullerian degenerates (from AMH), testes descend

• No testes → no testicular hormones. Mullerian system develops Wolffian degenerates

What determines the development of testes

Gonads are biopotential. Sry gene on Y chomsone encodes for Testis-determinng factor

fetal testosterone is converted into estradiol by__________

aromatase, which then influences the development of masculine traits. Alpha-fetoprotein blocks estradiol in females, while in males, estradiol promotes masculine development.

What regulates the release of sex steroids from the gonads?

The Pituitary gland (Master gland) Two sections: Posterior pituitary Anterior pituitary-releases hormones that make other glands release

• Anterior Pituitary gland stimulates hormones

Hypothalamus

Posterior pituitary receives neural input from hypothalamus: Vasopressin: water absorption hormone. Oxytocin: labor and lactation “love drug

• Anterior pituitary-No direct neuronal connections.

Hypothalmus makes its owns special homrones called?

releasing Hormones

• Hypothalamopituitary portal system-Releasing hormones Travel through the portal system to the anterior pituitary.

• Induces or inhibits stimulating hormones from pituitary that travel to other glands, such as the gonads or adrenal glands

HPG axis: Hypothalamic-Pituitary-Gonadal axis

• Regulation

  • Hormonal

  • Neural

  • Other

  • Chemical

  • Experience

Female gonadal Hormones-Menstrual vs. Estrus cycle (cyclic)

Surges of estrogen and progesterone initiate estrus.

Estrus- Period of fertility and receptivity(Lordosis) and proceptivity)attraction behviors

Animal Estrus-copulating is under hormonal control.

• Human females – sexual activity is not directly tied to cycle

• Women can engage in sex throughout their menstrual cycle

Medial Preoptic Area of the Hypothalamus (MPA)

Called the Sexually dimorphic Nucleus (SDN)

• Destruction abolishes sexual behavior in all mammalian males

• Stimulation elicits copulatory behaviors in males

• Larger in males, due to estradiol exposure shortly after birth

• SDN size correlates with male sexual behavior

Ventromedial Nucleus of the Hypothalamus (VMN)

Contains circuits critical for female rat sexual behavior.Lesions eliminate lordosis behavior

• Projects to the periaqueductal gray (PAG) in the midbrain

• PAG lesions eliminate lordosis

• Injecting P and E in VMN induces lordosis

Congenital Adrenal Hyperplasia (CAH)

Genetic (XX) females that produce high amount of androgens from adrenal cortex

• Leads to some masculinization of genitals

• XY males develop normally

Androgen Insensitivity Syndrome (AIS)

Genetic males (XY) who do not respond to androgens. External genitalia are female and breasts develop at puberty (effects of E)

• Gonads are testes, so they can’t bear children

• Production of anti-mullerian hormone - female reproductive ducts do not develop

5-α Reductase Deficiency (“Guevedoces”)

Genetic males, but lack the enzyme that converts T to DHT in the body during development. Appear female at birth, often initially raised as girls

• At puberty, testes descend (more T), body is masculinized

• Ultimately appear male but limited facial hair