Exam 5: Intro to Repro Endocrinology Flashcards
What does a 3% increase in reproductive rates equate to?
1 million more beef calves per year
- 2 million pigs per year
- 7 million gallons of milk per year
What does the endocrine system use hormones to do?
Bathe cells in body tissues
What allows for the precise control over reproductive function in both the male and female?
The interaction of anatomical structures, hormones, and target tissues
What is secretion, transport, and clearance controlled by?
Feedback mechanisms
What does transport depend on?
Water solubility or whether the hormone is protein bound
What does clearance occur via?
Metabolic destruction
Binding with tissues
Hepatic excretion
Renal excretion
Where do reproductive hormones come from?
Hypothalamus
Pituitary gland
Gonads
Describe the hypothalamus
The master organ
Combination of neuro and endocrine center
What does the hypothalamus regulate?
Endocrine system Body temperature Appetite Sexual behavior Fear/rage centers
What does the hypothalamus control?
Action of the pituitary through the median eminence
What does the median eminence do?
Connects the hypothalamus with the pituitary
What does the hypothalamus secrete?
Gonadotropin Releasing Hormone (GnRH)
What specifically secretes GnRH?
The axon of neurons
How does GnRH get to the pituitary?
Enters into the portal system and is carried locally to the pituitary
Describe the anterior pituitary
Located just below the hypothalamus
Receives GnRH from hypothalamus via portal system
What does the anterior pituitary release?
Lutenizing hormone (LH) Follicle stimulating hormone (FSH)
Can you get LH as a pharmaceutical?
No, but you can get products that act like LH
What does LH drive?
Ovulation
What can FSH do?
Increase the amount of follicular waves
It is used to superovulate cows
Describe the surge center
Releases large volumes of GnRH
This surge of GnRH will then have a LH surge
Describe the tonic center
Slow, consistent release of GnRH
What is the posterior pituitary the site of?
Oxytocin release
Describe oxytocin
Formed in the parventricular nuclei of hypothalamus and travels down nerve ending to the posterior pituitary where it is eventually released by exocytosis
What kind of hormone is oxytocin?
Neuroendocrine
What do the gonads receive?
Hormonal stimulation from the gonadotropins released from the AP (FSH and LH)
What do the testicles secrete?
Testosterone
Estrogen
What does LH act on in the testicles?
The Leydig cells to secrete testosterone
What does FSH stimulate in the testicles?
The Sertoli cells to produce estrogen from testosterone
What are the sertoli cells responsible for?
Spermatogenesis
What is testosterone responsible for?
Distinguishing characteristics of males
Maleness
Penis/scrotum formation
What is the SRY gene?
The sex determining region of the Y chromosome that causes genital ridge to produce testosterone and become testes
Testicular descent
Muscle formation
What do the ovaries secrete?
Estrogen
Progesterone
What does FSH act on the ovary (follicle) to do?
Produce estrogen and stimulate follicular development
What does LH act on the ovary to do?
Stimulate ovulation and corpus luteum funciton
Describe the process to start ovulation
Hypothalamus produces GnRH acting on the AP to produce of FSH and LH
FSH and LH act on ovary to stimulate follicular development
The follicle produces estrogen, which has a positive feedback early on
Estrogen drives the cycle faster
Ultimately, enough feedback causes a surge of GnRH, which causes a surge in LH which causes ovulation
What does inhibin do?
It has a negative feedback on FSH and suppresses additional FSH release
Why is suppressing additional FSH release important?
It stops the process and keeps cows from being a litter bearing species
What occurs once the animal ovulates?
There is a CL that produces progesterone, which has a negative feedback on the hypothalamus and pituitary
What can progesterone do to the stallion? Why?
Dampen the activity/attitude
It has a negative feedback on the hypothalamus and suppresses LH thus dampening testosterone production
Describe the male system of hormone release
Hypothalamus releases GnRH, which has a positive feedback on the AP
AP releases LH and FSH
LH has a positive feedback on Leydig cells causing the release of testosterone
FSH has a positive feedback on Sertoli cells which causes spermatogenesis and the release of inhibin
What are the actions of testosterone?
Positive feedback on virilizing effects
Negative feedback on hypothalamus and AP
Positive feedback on Sertoli cells
What are the actions of inhibin?
Negative feedback on hypothalamus and AP
