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Therio Exam 1 > Endocrinology > Flashcards

Endocrinology Flashcards

Lectures 1-3

1
Q

Which species has a prominent cranial vagina that can be used to assess cyclicity?

A

Bitch

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2
Q

What part of the hypothalamic nuclei regulates GnRH?

A 
Tonic center (in males and females, (responds to - feedback from decreased progesterone due to luteolysis) small pulses of GnRH stimulates the release of FSH and LH from AP)
Surge center (in females only (responds to + feedback due to high estrogen levels from the follicle in the absence of progesterone) releases large amounts of GnRH that stimulates release of LH for ovulation)
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3
Q

What system does the anterior pituitary use to release LH and FSH (when signalled by the surge and tonic center)?

A

Hypothalamo-hypophyseal portal system

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4
Q

What is the function of the posterior pituitary?

A

Paraventricular nucleus excites PP to release oxytocin

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5
Q

What are the key players of the Hypothalamo- Pituitary Gonadal Axis (HPG axis) that regulate reproduction?

A

GnRH (hypothalamic nuclei), gonadotropins (FSH, LH, prolactin - AP), and oxytocin (PP)

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6
Q

What steroids can cholesterol be broken down to?

A

Progesterone, estradiol (=FSH), or testosterone

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7
Q

Where does the prostaglandin (PGF2a) come from and what does it target?

A

Source: uterus
Target: epididymis (males) or CL, uterine myometrium, ovulatory follicles (females)
Cause: cramping of uterus (process of luteolysis/contractions) and promotes uterine tone

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8
Q

What does the prostaglandin (PGE2) do?

A

Relaxes

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9
Q

Why do high producing dairy cows have large livers?

A

Steroids are metabolized via the liver

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10
Q

The paramesonephric tubules are most fused in what animal?

A

Horse

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11
Q

How long is the estrous cycle in cattle and horses?

A

21 days (ovulation to ovulation)

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12
Q

What are some examples of polyestrus animals?

A

Cattle, swine

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13
Q

What are some examples of seasonally polyestrus animals?

A

Short day: sheep, goat

Long day: mare

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14
Q

What are some examples of monoestrus animals?

A

Bitch

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15
Q

What is the dominant hormone during the follicular phase (proestrus - estrus)?

A

Estrogen (E2) - formation of ovulatory follicles to ovulation

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16
Q

What is the dominant hormone during the luteal phase (metestrus - diestrus)?

A

Progesterone (P4) - ovulation to CL regression (ends with luteolysis)

17
Q

How long is the estrous cycle in a bitch?

A

4-8 months (7-9d in estrus and 60-80d in diestrus)

No MRP so they wait 2 months to find out if pregnant

18
Q

Why are queens an exception to estrus behavior?

A

Induced ovulators
Inter-estrus period if not mated (=postestrus) is 7-14d = no ovulation, follicular atresia and then go back into heat (no metestrus or diestrus period)

19
Q

Why is the bitch not fertilized right after ovulation as with other animals?

A

Release primary oocyte during ovulation (2-3d after LH surge) that must ovulate over ~9d (extended time in heat) before she can be fertilized

20
Q

During the follicular phase, what causes the decline in progesterone?

A

Regression of the CL (luteolysis)

21
Q

What hormone levels are associated with surge release of LH?

A

Low progesterone and high estrogen

22
Q

What is the dominant hormone during the recruitment phase of follicular dynamics?

A

FSH - recruits new wave of follicles form ovarian pool

23
Q

What are the dominant hormones during the selection phase of follicular dynamics?

A

Low FSH and moderate LH - selected follicles progress and release estrogen and inhibin to cause other follicles to undergo atresia

24
Q

What is the dominant hormone during the dominance phase of follicular dynamics?

A

LH (dominant follicle has LH receptors) - produces high levels of estrogen and inhibin

25
Q

Where does the estrogen come from?

A

LH binds theca interna cells to produce testosterone that goes to granulosa cells for FSH-binding –causes conversion of testosterone to estrogen

26
Q

How long do most species spend in LH surge?

A

~24h (except mare, 3-5d) and bitch, waits 2-3d after LH surge to ovulate

27
Q

How is the corpus luteum formed?

A

Transformation of outer theca (small luteal cells) and inner granulosa (large luteal cells) of the follicle which then produces progesterone (neg feedback)

28
Q

What animal cannot be short cycled (return to estrus after CL formation)?

A

Sow (litter species) need a longer maturation time within metestrus to ovulate all follicles at once (very short diestrus period unlike cows and mares)

29
Q

What is the luteolytic agent in domestic animas?

A

PGF2a (reduces as oxytocin decreases from the CL disintegration)

Therio Exam 1 (4 decks)

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