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Animals Repro > Reproductive Cyclicity (lec 8) > Flashcards

Reproductive Cyclicity (lec 8) Flashcards

1
Q

What is the oestrous cycle?

A

After puberty female enters a period of reproductive cyclicity - defined as the period between the start of two period of oestrus

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2
Q

What is the importance of oestrous cycles?

A

Provide females the repeated opportunity to copulate and become pregnant

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3
Q

What are the two primary behavioural events of oestrous cycle?

A
  1. sexual receptivity
  2. Copulation (sexual inter course)
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4
Q

When conception/pregnancy occurs, what oestrous cycle do they enter?

A

Anoestrus

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5
Q

What hormone increases during oestrous?

A

Increase of estrogen

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6
Q

Animals have different types of cycles. What types of oestrous cycles are there, give an example with an animal`

A
  1. Polyestrus - Cow, queen, pig and rodents
  2. Seasonal polyestus (long day) - mare
  3. Seasonal Polyestrus (short day) - ewe, doe, elk, nanny
  4. Monoestrus - dog, wolf, fox, bear
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7
Q

what are the two major phases of oestrous cycle? and what phases do they cover?

A
  1. follicular Phase - the period from the regression of corpora lutea to ovulation
  2. Luteal Phase - period from ovulation until the corpora lutea regression
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8
Q

How long is the follicular phase in comparison to luteal phase?

A

20% for follicular phase, and 80% for luteal phase

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9
Q

What are the dominant primary ovarian structures of follicular phase? and what dominant reproductive hormone is produce?

A

Preovulatory follicles which release oestradiol
(an estrogen hormone that is important for release of eggs and getting pregnant)

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10
Q

What are the dominant primary ovarian structures of Luteal phase? and what dominant reproductive hormone is produce?

A

Corpora lutea which releases progestrone

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11
Q

Although the luteal phase is dominated by progesterone from the Corpus Luteum , do follicles cease to develop?

A

False, they continue to develop and regress during this phase but none go on to become pre-ovulatory and there is no oestrous behaviour expressed.

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12
Q

What are the four stages of oestrus in follicular phase and Luteal Phase can be divided into?

A

Follicular Phase
1. Pro-oestrus
2. Oestrus

Luteal Phase
3. Metoestrus
4. Dioestrus

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13
Q

when does is pro-oestrus occur? how is is characterised and long does is averagely go for

A

When progesterone declines as a result of luteolysis

characterised by the endocrine transition from a period of progestrone dominance to a period of estrogen dominance

2-5 days

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14
Q

What is luteolysis?

A

Destruction of the corpus luetum

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15
Q

what occurs during pro-oestrus and what are the primary hormones?

A

Pro-estrus follicles are recruited fro ovulation and the female Repro system prepares for the onset of oestrus and mating

primary hormones: FSH and LH

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16
Q

what is oestrus? and how long does it typically go for?

A

is the period during which the female allows copulation

oestrus can vary in length between species

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17
Q

How is oestrus characterised?

A

by visible behaviours symptoms such as sexual receptivity and mating

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18
Q

What is the major hormone used during oestrus?

A

Oestradiol - induces behavior changes and major physiological changes in the repro tract

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19
Q

what is standing oestrus?

A

During early oestrus she will not normally accept the male but as oestrus progresses so does the female’s willingness to accept the male

20
Q

How do pigs use standing oestrus for oestrus detection?

A

Lordosis - arching of back

21
Q

what is metoestrus?

A

Is the transition from oestrogen dominance to progesterone secretion

22
Q

when do metoestrus occur?

A

period between ovulation and the formation of the function Corpus lutea

23
Q

What are the levels of both oestrogen and progesterone?

A

relatively Low

24
Q

What is luteinisation, and what phase does this occur?

A

When the follicle gets transformed into a corpus luteum at Metoestrus phase.

25
Q

How long does is take a female to produce significant quantities of progesterone?`

A

2-5 days

26
Q

What is dioestrus?

A

The period of maximum Luteal function, period when the CL is full functional and progesterone production is high

27
Q

When does the dioestrus phase end?

A

When the CL is destoryed - luteolysis

28
Q

What is the main hormone used in Dioestrus? and what effect does it have?

A

Progestrone, prompts the uterus to prepare a suitable environment for the embryo and eventual attachment of the conceptus
to the endometrium

29
Q

Is there sexual activity involved during the dioestrus phase?

A

no

30
Q

How long does Dioestrus occur in domestic animals?

A

10-14days (Depends on the functionality of the CL)

31
Q

What is an example of a Monoestrus mammal, and what are or how do they differ from key features of the estrus cycle?

A

Wolves (once per year)
The oestrus cycle still formed of two phases, follicular phase and luteal phase. The follicular phase is still comprised of pro-oestrus and oestrus, but the luteal phase is only comprised of dioestrus - metoestrus is absent (formation of CL).

means they have alonger period of anestrus, FSH is coming from Pituitary gland, because there is no inhibin

LH remains low up until proestrus begin (priming the cycle for follicular phase) 9 days. Estrogen increases and then suddenly increases LH at end of proestrus, FSH increases -

Another main difference is; Ovulation only occurs 3 days after the peak of LH in the estrus phase. As oocyte is not mature until 3 days later

levels of progesterone increases in estrus (unlike cow)

32
Q

Why is the FSH levels high in anestus phase?

A

because there are no ovarian follicles, so no inhibin and no negative feedback on FSH.

33
Q

What animal is polyoestrous? and how do cats cycles differ from other animals?

A

There are repeated Oestrous cycle but no ovulation until stimulated (induced ovulators) Can;t ovulate without male

With no male - repeated oestrus cycles, repeated levels of estrogen - no ovulation
The progestrone remains low until stimulation/pregnancy as there is no Corpus Luteum.

Postestrus - short cycle intervals between two Estrogen level peaks (no mating/pregnancy)

when mating occurs - ovulation occurs due to stimulation - neural response causes ovulation - CL begins to be formed so progesterone increases.

34
Q

What oestrus cycle do horses have?

A

They are seasonal polyoestrous
they can fall pregnant in spring/summer.

difference
1. ovulation occurs before the peak of LH
2.middle of luteal phase you have an elevation of FSH

35
Q

What does anoestrus mean?

A

without cyclicity, not a phase of the oestrous cycle but a period where is no oestrous cycle activity.

36
Q

Are ovaries active during anoestrus?

A

ovaries are inactive

37
Q

What causes anoestrus?

A

By insufficient GnRH release from the hypothalamus to stimulate FSH and LH secretion

38
Q

What the major causes of anoestrus?

A
  • Gestational anoestrus
  • Seasonal anoestrus
  • Lactational anoestrus
  • Nutritional anoestrus
  • Stress induced anoestrus
  • Pathological anoestrus
39
Q

How gestation affect anoestrus?

A
  1. Gestational anoestrus - inhibition of GnRH, LH and FSH by progesterone. The elevated levels of P4 from the corpus luteum/or placenta exerts a negative feedback on GnRH neurons which inhibit FSH and LH secretion from the anterior pituitary
40
Q

How do seasons affect anoestrus?

A

Seasonal Anoestrus -

  1. In summer, Uv light hits the photoreceptors in the eyes, the retinal nerves are stimulated and synapsed signal travels down the optic nerve to the suprachiasmatic nucleus.
  2. This excitatory response stimulates the superior cervical ganglion of the brain, they innervate the pineal gland. In the pineal gland, excitatory signals are then converted to inhibitory response, where low levels of noadrenaline are secreted, levels of melatonin from the pineal glands are also low. Thus having an affect on the hypothalamus.
  3. In the hypothalamus are RFRP neurons, the low melatonin release, produce more of the RFRP-3 peptide
  4. long day breeder = high levels of RFRP from light stimulation (less melatonin), will cause stimulation of other neurons in hypothalamus called Kiss neurons. Causes stimulations of Kiss-10 peptin, and then release of GnRH release.
  5. short day breeder = decrease in levels of RFRP due to increase in melatonin, kiss neurons are inhibited, decrease in kiss-10 , less GnRH
41
Q

What animals have lactional anoestrus? and what is the thought process behind it

A

Lactation suppresses GnRH release through elevated secretion of prolactin and suckling of neonate

Mare - experience post partum oestrus (foal heat) but lapse into lactational anoestrus/irregular cycles

Alpaca - no lactational anoestrus

Sow - complete suppression of cyclicity until weaning

Cow - lactation suppression of cyclicity for up to 60 days.

42
Q

how does suckling frequency have a direct effect on cyclicity?

A

The number of suckling sessions between 3-20 per day causes the cow to remain in lactional anoestrus, therefore low levels of LH. When suckling decreases, LH increases.

43
Q

What are other effects that inhibit GnRH during the post-partum period

A
  1. visual encounter with THEIR offspring
  2. olfactory encounter with THEIR offspring
  3. auditory encounter with THEIR offspring
44
Q

Do bitches have lactational anoestrus?

A

No lactional anoestrus - independent of lactation

45
Q

Do Queens have lactational anoestrus?

A

no lactational anoestrus - post-partum ovulation and mating

46
Q

What is the mechanism behind nutritional anoestrus?

A

levels of leptin (direct relationship with hypothalamus - neurons that produce GnRH)

47
Q

What is the impact of stress on anoestrus?

A

close relationship between stress levels, stress activates the hypothalamic pituitary-adrenal axis but suppresses the hypothalamic-pituitary -gonadal axis

Animals Repro (8 decks)

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