Reproductive Endocrinology Flashcards
The endocrine system uses _____ and _____
Hormones; chemical messengers
Hormones secreted influence function of target cells at _______
Distant sites
A hormone can be either _______ or _______
Endocrine; neuroendocrine
_______, ________, and ______ are controlled by feedback mechanisms
Secretion, transport, and clearance
Transport depends on
- water solubility
- whether a hormone is protein bound
Clearance via
- metabolic destruction
- binding with tissues
- hepatic excretion
- renal excretion
What are the 3 anatomical structures that produce reproductive hormones?
- hypothalamus
- pituitary gland
- gonads (testicles, ovaries)
What is considered to be the “master organ”?
Hypothalamus
- has a combo neuro and endocrine center
The hypothalamus regulates
- endocrine system
- body temp
- appetite
- sexual behavior
- fear/rage centers
The hypothalamus controls the action of the ______
Pituitary
Median eminence
Connects hypothalamus with the pituitary
The portal vessel communicates with the ______
Anterior pituitary
The hypothalamus secretes _____
Gonadotropin releasing hormone (GNRH)
- secreted by axons
- enters into portal system and carried to pituitary
Anterior pituitary
- located below hypothalamus
- receives GnRH via portal system
AP releases ____ and ______
- lutenizing hormone (LH)
- follicle stimulating hormone (FSH)
_____ drives ovulation
LH
- is possible to stimulate an endogenous LH surge via GnRH
- could use HCG with LH-like properties
______ drives follicular waves in cattle
FSH
- is exploited to super-ovulate cattle
Release of GnRH
- surge center: releases large volume of GnRH
- tonic center: slow, consistent release of GnRH, and can “gush” GnRH right before ovulation
Release of oxytocin
Hypothalamus makes oxytocin that is released from the posterior lobe of the pituitary
Oxytocin
Formed in paraventricular nuclei of hypothalamus
- travels down nerve endings to posterior pituitary
- released by exocytosis
Oxytocin is a _______ hormone
Neuroendocrine
Oxytocin assists with
- milk let down
- uterine contractions
Gonads
Receive hormonal stimulation from the gonadotropins released from the anterior pituitary
- FSH and LH
Testicles secrete ____ and _____
Testosterone; estrogen
LH acts on ______ to secrete ______ (males)
Leydig cells; testosterone
FSH stimulates _____ to produce _____ from testosterone
Sertoli cells; estrogen
Testosterone
Responsible for male characteristics
- penis/scrotum formation
- testicular descent
- muscle formation
SRY gene
Causes genital ridge to produce testosterone and become testes
= male phenotypic sex results
Ovaries secrete ____ and _____
Estrogen; progesterone
FSH acts on the _____ to produce _____ (female)
Ovary (follicle); estrogen
- stimulates follicular development
LH acts on the _____ to stimulate _____ (female)
Ovary; ovulation
- corpus luteum function
What happens before ovulation?
Hypothalamus produces GnRH –> AP produces LH and FSH –> acts on ovary = follicular development –> follicle produces estrogen –> E2 has + feedback to the surge center and drives the cycle –> threshold of + feedback leads to GnRH surge –> tremendous release of LH = ovulation
Inhibin
Suppresses additional LH release
- stops the positive feedback process and keeps animal from being a litter bearing species
You could flood with _____ to override inhibin
LH
What is happening after ovulation?
Corpus luteum produces progesterone –> - feedback to hypothalamus and anterior pituitary
You could give a stallion ______ to regulate their behavior
Progesterone
Male feedback system
GnRH produced by hypothalamus —> causes pituitary to produce LH and FSH, which has + effect on Leydig and Sertoli —> Leydig secretes testosterone = virilizing effects (+), behavioral effects, and a + effect on sertoli cells —> Sertoli cell does spermatogenesis (+), or secretes inhibin which has negative feedback on pituitary and hypothalamus
Testosterone has negative feedback on the _____ and ______
Pituitary and hypothalamus
