09 - Ovulation

Question 1

(Ovulation)

1. In all mammals studied, what is the event that starts the cascade for ovulation?

2-3. The surge may occur in what two ways?

4. The interval from surge to ovulation varies with species… how long in rabbit? in women and mares?
5. The follicle does not rupture under the influence of intrafollicular pressure per se. Rather…. what is the current hypothesis?
6. The egg and surrounding cumulus oophorus are usually expelled how soon after follicular rupture?

Answer 1

1. the gonadotropin surge
2. spontaneously (spontaneous ovulators) ue to feedback mechanisms in the hypothalamo-pituitary-ovarian axis
3. induced by stimuli of mating (induced or reflex)
4. 10 hours, 36 hours
5. result of inflammatory cascade that weakens the follicular wall
6. within 2 minutes (signalling completion of the process)

Question 2

(Induced Ovulation)

1. Diverse species are induced ovulators including:

ferret, mink, rabbit, domestic cat, racoons, beavers, voles and new-and-old-world camelids

2. The LH surge of induced ovulators is caused by what?
3. The sensory receptors or fields are not restricted to the genital area (vagina, cervix, sperm deposition), but also include body surface tactile receptors, olfactory, visual and auditory stimuli.

To successfully induce an LH surge, mating usually must activate several of these.

4. Will a single mating always be enough to induce?

Answer 2

2. a neuroendocrine reflex activated by mating
3. no, sometimes multiple matings are required

Question 3

(Induced Ovulation Cont)

1. The mating causes what (hormonally)?

This is an example of neuroendocrine reflex… how?

2. The female needs to be what for a surge release to occur in response to mating?

Answer 3

1. increased GnRH release from the hypothalamus which then triggers LH release.

afferent arc is neural, efferent arc is endocrine

2. estrogen dominated (ie be in estrus)

Question 4

(Induced Ovulation Cont)

1. In the absence of mating there is no ovulation… what happens to the large follicles?
2. The female leaves estrus to a what?

Answer 4

1. lose dominance and become artetic.
2. short anestrus (aka intestrus or postestrus) lasting 1-2 weeks while a new wave of follicles develops

When these are sufficiently mature she will move
into the next proestrus and then estrus.

Question 5

(Induced Ovulation)

1. The division of species between spontaneous and induced ovulators is not always strict.
2. Facultative reflex ovulation is where copulation hastens ovulation is a species generally considered what?
3. An ovulation-inducing factor (OIF) has also been demonstrated in the seminal plasma of camelids (old and new world) which can induce an LH surge even if what?

Answer 5

2. spontaneous (while occasional spontaneous ovulations occur in species that are generally induced ovulators
3. given by intramuscular injection

(it is much larger than GnRH but acts in a similar manner on the pituitary)