Chapter 8 Flashcards by Nicole Sederstrom

What are the key mechanisms of the Follicular Phase?

Regulation of FSH and LH (gonadotropins) secretion
Follicular growth and atresia
E2 and P4 secretion
- and - feedback
Ovulation
Oocyte growth and maturation

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What is the result in the gonadotropin hormonal cascade? (increase FSH, LH)

increase follicular growth, increase estradiol secretion, increase Estrus (sexual receptivity), GnRH surge causes and LH increase leading to oocyte maturation and finally ovulation

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The onset of follicular development is _______ of CL (__________)

Lysis

Luteolysis

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What are the steps to Preovulatory LH surge?

*decrease P4 from CL then increase GnRH leading to an increase of FSH and LH all leading to a Proestrual follicular Development.
*There is an increase of inhibin (secreted from maturing folliclue) leading to decrease in FSH
AND… increase estradiol to threshold leading to preovulatory LH surge

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GnRH from hypothalamus is anterior pituitary by _______________

Primary Portal Plexus (PPP)

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Anterior lobe then has ________________, causing an increase in FSH and LH

Secondary portal plexus

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What does the tonic center control?

small spikes of GnRH that occurs infrequently over time. (development of follicle)

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During the follicular phase the what is the frequency of GnRH?

1.5 to 2 hours

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During the luteal phase what is the frequency of GnRH?

4 to 8 hours

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What does the surge center control?

Under the influence of high levels of E2= high amplitude of GnRH release

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With threshold of E2 reached a “gush” of ________ releases, a pre-ovulatory surge of LH occurs

GnRH

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What are the 2 mechanisms of the LH surge?

- feedback= spontaneous ovulators

2. Neural reflec= induced ovulator

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What happens in the + feedback = spontaneous ovulators?

threshold E2 stimulates GnRH surge, therefore LH surge which results in OVULATION
ex. cows, sows, ewes, mares, women

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What happens in the Neural reflex= induced ovulator?

Copulation results in GnRH surge and LH surge resulting in OVULATION
ex. rabbits, felids, ferrets, mink, camelids

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Sustained copulation for Camelids, and Lions

Camelids= 30 minutes

Lions over 100 times per estrus period

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What happens when an induced ovulator?

Penile modification for sensory nerve stimulation

ex. spikes on penis (cat), hard bone (alpaca)

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Define Inhibin.

Selectively suppresses secretion of FSH

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What are the roles of inhibin?

Negative feedback on FSH without affecting LH

2. E2 also has negative feedback on FSH secretion

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What are the stages of estrous cycle?

diestrus, proestrus, estrus, metestrus

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What are the phases of the estrous cycle? which stages go with the phases?

Follicular phase= proestrus and estrus

Luteal phase= metestrus and diestrus

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What is the key event driving onset of proestrus?

Luteolysis, a drop in P4

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Why is there a limited FSH surge is estrus?

because of inhibin, and possibly E2, negative feedback

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_____________ has both theca interna and granulosa cells

Antral Follicle

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What role is played by the theca and granulosa cells?

E2 synthesis

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_____________: have receptor LH (glycoprotein); when bound casacade results in T4 production, which enters the ________________

Theca Interna Cells | Granulosa cells

______________: have FSH (glycoprotein) receptors, when FSH is bound to receptor, uses different protein kinase to then activate the aromatase system to convert T4 to E2.

Granulosa cells

E2 (steroid) can then act on the "rest of the body", primary target is:

Reproductive Tract (proestrus and estrus)

How does E2 affect the repro tract?

increase blood flow, edema, secretion of mucus, leukocytes, smoothe muscle motility, and growth of uterine glands

________ acts also on the brain for reproductive behaviors

Lordosis, Phonation "________", inc. activity

mating cells

Follicular dynamics (3)

Growth and atresia (degeneration) all stages of cyctle complete growth and ovulation- low P4

Follicular wave Generation and Atresia: What are the three stages of a follicle?

Recruited, Selected, and Dominant

Which Follicles are FSH dependent?

Recruited

Which Follicles are LH Dependent?

Selected and dominant

Why do some follicles undergo atresia?

There is not enough LH receptors

What is low progesterone required for?

maturation of follicle

In women, follicuclar atresia results in follicular delption which is called?

Menopause

What is menopause?

cessation of menstruation, lack of cyclicity (near 50 years of age)

Post menopausal is due to low estradiol, what happens?

genital atrophy, decreased secretion, modified lipid metabolism, bone loss, "hot flashes"

T or F. Can treat with hormone replacement therapy, which leads to animal welfare issues.

True

What does a pre- ovulatory surge of LH cause (in the ovary)?

Hyperemia ( local elevated blood flow)

What is hyperemia controlled by?

histamine and Prostaglandin

In the ovary, Theca interna become _________ because of increased vascular permeability caused by histamine.

Edematous

Follicles also produce ____________ which promote growth of new blood vessels (aids in follicle controlling its own blood)

angiogenic factors

This is secreted by a pre- ov surge of LH that increases contraction for smooth muscles within ovary. (increase follicular pressure); and release of lysosomal enzymes within follicle

Prostaglandin

How is the follicle wall weaken?

stigma: apex of the follicle, pushes outwards and weakens

A shift from E2 to P4 secretion by DF is due to what?

High LH

P4 promotes collagenase, What is collagenase?

breaks down follicle wall

What causes gap junction breakdown?

Pre-ov LH surge

T or F. Granulosa cell projections do not penetrate through cell membrane and then zona pellucida

False, do

T or F. GC cell projections formed gap junctions with the oocyte plasma membrane and eventually with zona pellucida during oogenesis

True

T or F. GC are believed to govern oocyte grouwth and meiotic activity

True

Closure of gap jxns removed inhibition of meiosis and allow __________________

resumption of oogenesis

T or F. dominant follicle "poised" to stop meiosis by degradation of gap jxn

False, resume

What receptors are present on the theca interna cells?

LH receptors

What receptors are present of the granulosa cells?

FSH receptors

What is removing inhibition of meiosis called?

Meiotic arrest lifted

What 2 factors believed to control nuclear arrest?

1. cAMP from provided by GC gap jxn | 2. OMI (oocyte meiotic inhibitor)

What happens in the 1st meiotic division? (except dog and fox)

formation of the 1st polar body often prior to ovulation in most mammals

What happens in the 2nd meiotic division?

formation of 2nd polar body; haploid condition, allowing zypgote to be 2N, half of the DNA material from each germ cell