Lecture 70: Reproductive Endocrinology Flashcards
The _____________ is the neural control center for repro hormones.
Hypothalamus
Describe the simple neural reflex of regulation of reproduction
Employs the nerves that release simple neurotransmitters directly into target tissue
Describe the Neuroendocrine Reflex regulation of reproduction
Requires a neurohormone (released by a neuron) to enter the blood and act on remote target tissue
The pituitary gland is positioned in the depression of the sphenoid bone, called the _______ _______.
Stella turcica
The third ventricle separates the ________ portions of the hypothalamus.
Lateral
What is the Hypothalamo-Hypophyseal Portal System (HHP)?
The HHP system allows minute (picograms) quantities of releasing hormones to act on the anterior pituitary before they are diluted by the general circulation
What is the relationship between the portal vascular system (PVN) and the posterior pituitary?
Axons from neurons originating in the hypothalamus (PVN) extend into the posterior pituitary where they release their neurohormones into a capillary plexus
True or False: The posterior pituitary has a portal system.
FALSE
Neurohormones are deposited directly into systemic circulation
Which repro hormones are classified as hypothalamic hormones?
Gonadotropin Releasing Hormones (GnRH)
Which repro hormones are classified as Pituitary Hormones?
Follicle Stimulating Hormone (FSH)
Luteinizing Hormone (LH)
Prolactin
Oxytocin
Which repro hormones are classified as gonadal hormones?
Estradiol (E2)
Progesterone (P4)
Prostaglandin F2-alpha
Equine Chorionic Gonadotropin (ECG)
Human Chorionic Gonadotropin (HCG)
Which repro hormones are classified as neurohormones and what is their mode of action
GnRH, FSH, LH, Oxytocin
Synthesized by neurone and are released directly into the blood to cause a response in a target tissue somewhere else in the body
Which repro hormones are classified as releasing hormones and what is their mode of action
GnRH
- Synthesized by neurons in the hypothalamus and causes release of other hormones from the anterior pituitary
- They can also be classified as neurohormones because they are synthesized and released by neurons
Which repro hormones are classified as sexual promoters and what is their mode of action
Estrogen, Progesterone, Testosterone, cEG, hCG
- Secreted by the gonads to stimulate the repro tract, regulate the function of the hypothalamus and anterior pituitary, and regulate reproductive behavior
Which repro hormones are classified as pregnancy maintenance hormones and what is their mode of action
Progestins and Placental Lactogen
High concentration during pregnancy
Responsible for maintaining pregnancy and assisting the female in lactation ability
Which repro hormones are classified as luteolytic hormones and what is their mode of action
PGF2-alpha
Causes destruction of the corpus luteum
Which repro hormones are classified as general metabolic hormones and what is their mode of action
Thyroxin, Adrenal corticoids, and growth hormone
Promote metabolic well-being
State which repro hormones are biochemically classified as peptides, glycoproteins, steroids, and prostaglandins
Peptides: GnRH is a decapeptide, Prolactin and Relaxin
Glycoproteins: FSH, LH, Inhibin
Steroids: Progesterone, estradiol, testosterone
Prostaglandins: PGF2-alpha and PGE2
Protein hormones bind to what type of receptors?
Plasma bound receptors
Steroid hormones bind to what type of receptors?
Travel freely through plasma membrane into the cytoplasm and bind directly to specific nuclear receptors
Describe the difference in a fast response vs slow response from a steroid hormone. Give examples of each
Fast response: binds to a membrane receptor causing protein production
example: Estradiol increases myometrial contractions and progesterone decreases myometrial contractions
Slow response: Binds to nuclear receptor inside cell causing protein production
example: estradiol causes mucous secretion by the female tract and progesterone causes uterine gland secretion
How does the CNS regulate the reproductive system?
Receives, processes and interprets sensory inputs (such as olfactory, visual, feedback systems, and photoperiod
These inputs ultimately regulates GnRH release
What is the main role of the hypothalamo-pituitary gonadal axis?
Regulates reproduction based upon a positive and negative feedback system
Hormones can have both positive and negative feedback on different areas
Steroid hormones are metabolized where? What about protein hormones?
Steroid hormones are metabolized by the liver
Protein hormones are degraded in the liver and kidneys
Which of the following does the pituitary secrete?
A) Oxytocin, FSH, LH
B) Testosterone and Inhibin
C) FSH and Progesterone
D) Estrogen and Inhibin
Oxytocin, FSH and LH
Do males have a surge center?
NO!
The surge center in females is essential for ovulation, males obviously don’t need this
What is the mechanism of “Defeminization” in the male?
Testosterone produced by the testes of the developing male fetus penetrates the blood-brain barrier.
Once the testosterone is in the brain, it is converted to Estradiol
Actually is estradiol that defeminizes the hypothalamus and causes the surge center to not develop
How does estradiol not cause defeminization in the female brain?
In the female, estradiol is bound to alpha-fetoprotein which prevents the estradiol from crossing the blood brain barrier
What is puberty?
The process of acquiring reproductive competence
The onset of puberty is dependent upon what?
Dependent upon the ability of the hypothalamic neurons to produce GnRH in sufficient quantities to support gametogenesis
In the male, the onset of puberty is brought about because of decreased hypothalamic sensitivity to what?
Decreased hypothalamic sensitivity to negative feedback by Testosterone and Estradiol
What is a factor that causes accelerated puberty in sows?
Boar exposure (pheromones)
