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Animal Production > Puberty > Flashcards

Puberty Flashcards

1
Q

Periods of reproductive system

A

1.Fetal period
2. Prepubertal period
3. Reproductive period
4. Senescence period

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2
Q

Fetal period

A

-Sex determination, differentiation, and tract development and growth

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3
Q

Prepubertal period

A

Period between birth and puberty
-includes secondary sexual growth and development. Second half of this period will have higher reproductive growth rate than rest of body growth
-varies in time depending on species
-somatic and behavioural secondary sex characteristics appear

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4
Q

Different stages of prepubertal period

A

-Early, mid, late-prepubertal and peri-pubertal stages

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5
Q

Reproductive period

A

Sexual activity resulting in conception and production of offspring is possible

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6
Q

Senescence period

A

Reproductive function is no longer possible

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7
Q

Patterns of secretion of GnRH and LH release

A
  1. Pulsatile (episodic or tonic)- short spikes

2.Surge (phasic or preovulatory)- sustained/long term

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8
Q

What factor plays a major role in differential sexual development of female vs male?

A

alpha fetoprotein (alpha-FP)

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9
Q

Female sex determination

A

1.alpha-FP binds to estradiol preventing it from passing the blood-brain barrier and entering the brain

2.Hypothalamus is therefore “feminized” resulting in GnRH surge center developing

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10
Q

Male sex determination

A

1.Testosterone freely enters the brain since alpha-FP does not bind to it

  1. Testosterone in the brain is aromatized into estradiol
  2. Hypothalamus is “defeminized” so surge center does not develop
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11
Q

Differences in LH secretion between males and females

A

Males: Small LH pulses every 2-6hrs. Testosterone immediately follows.

Females: High amplitude surges of LH every several weeks. Pulsatile releases of LH happen between surges

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12
Q

GnRH secretion before puberty

A

Before puberty, in both males and females, the GnRH neurons in both the tonic and surge centers release low amplitude and low frequency pulses of GnRH

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13
Q

GnRH secretion after puberty

A

-Males: do not have surge center

-Females: tonic center increases pulse frequency controling basal levels of GnRH.
Surge center controls preovulatory surge of GnRH

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14
Q

Maturation after puberty

A

Sexual maturation, physical maturation, and fertility potential all continue beyond onset of puberty

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15
Q

Definition of puberty in animals

A

Age at which reproduction and parentage first becomes possible

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16
Q

Onset of puberty in different female animals

A

1.Age at first estrus- most practical

2.Age at first ovulation- more accurate, less practical because need palpation, ultrasonography or progesterone level checks

  1. Age at first attainment of ability to support pregnancy- not necessarily linked to 1st estrus or ovulation. Ex dairy cattle need threshold body size
17
Q

Onset of puberty in different male animals

A

1.Age when behavioural traits expressed
2.Age at first sperm produced
3. Age at first ejaculate
4. Age when ejaculate contains a threshold number of spermatozoa

18
Q

Bulls ejaculate spermatozoa threshold

A

-min of 50 million sperm with at least 10% motility

-will increase in numbers later

19
Q

Factors affecting rate of sexual maturation

A

-genetics
-nutrition
-season
-breed/race
-sexual/social associations
-environmental influences
-general health
-endocrine disruptors

20
Q

Range of puberty ages in different species

A

-great variation among different species

-even among a species, 50% of variations are due to genetics

21
Q

Effect of breed/race on puberty

A

-different breeds in a species vary greatly in age at puberty
>genetic selection and geographical locations

ex. African american girls reach puberty earlier (50% by age 9 vs 12% caucasians)
Ex. 18yrs for girls in high altitude regions of Asia

22
Q

Effect of nutrition on onset of puberty in dairy heifers

A

-Age at first parturition should be 24 mths and 1200lbs
*nutrition is main source in reduction of age

23
Q

Male exposures effect on age of puberty

A

Exposure to males will result in earlier maturity
-can be physical, visual or olfactory cues
-male exposure has stronger effect than group size

24
Q

Nutritions effect on puberty in humans

A

-Major source of puberty age reduction
>overweight kids reach puberty early
>Each decade for more than 100yrs, the age at puberty dropped by 4mths

25
Q

Growth rate effect on age of puberty

A

Higher growth rate will result in earlier maturity

26
Q

Effect of group size and male exposure on age of puberty

A

-Larger groups will reduce age of puberty AND male exposure will have stronger effect than group size

27
Q

Effect of season of birth on age at puberty

A

-Strong effect on seasonal breeders
>spring born lambs reach puberty at younger age; less synchronous
>fall born lambs take longer to reach puberty by are more synchronous

28
Q

What effects Kisspeptin neuron stimulation?

A

Stimulated by blood glucose, fatty acids, leptin levels
**indicators of nutrtion, metabolic status

NOTE: kisspeptin then stimulates GnRH neurons

28
Q

Effect of glucose on GnRH release

A

When glucose present, LH pulses occur hourly

When glucose inhibited, LH frequency and amplitude decreased

If exogenous GnRH present then LH spike could still occur

29
Q

Endocrine regulation of puberty

A

-Depends on ability to have high frequency and amplitude GnRH pulses

*does not depend on gonads, pituitary, or capacity to produce GnRH

30
Q

Gonadostat theory (before puberty)

A

Before puberty: hypothalamus is highly sensitive (from high level of estrogen receptors) to negative feedback of estradiol so GnRH is not released even with low levels of estradiol.

31
Q

Gonadostat theory (transition to puberty)

A

-Negative sensitivity of hypothalamus to estradiol is reduced allowing for a higher level of GnRH release

Animal Production (17 decks)

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