Puberty Flashcards

1
Q

What is the major difference between a male and female hypothalamus?

A

Males don’t have a surge center

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2
Q

Why does the male hypothalamus not have a surge center?

A

Testosterone defeminizes it and eliminates the surge center.

*NOTE: It is actually estradiol converted from testosterone that defeminizes

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3
Q

Why doesn’t the estradiol produced by females also eliminate the surge center?

A

Because it’s bound to alpha-fetoprotein and cannot cross the BBB.

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4
Q

How is puberty started?

A

GnRH at the right frequency stimulates gonadotropin release by the anterior pituitary.

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5
Q

What 3 things does puberty promote?

A

Gametogensis
Steroidogenesis
Development of reproductive tissues

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6
Q

Define sexual maturity.

A

Age at first ovulation

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7
Q

Define breeding maturity.

A

Age where a female can support pregnancy without problems.

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8
Q

What are 3 signs of puberty in a male?

A

Behavioural traits expressed
Age at first ejaculation
Age when first spermatozoa appear in ejaculate or urine

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9
Q

What is the average age for bovine puberty?

A

11 months

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10
Q

What is the average age for ovine puberty?

A

7 months

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11
Q

What is the average age for porcine puberty?

A

7 months male, 6 months female

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12
Q

What is the average age for equine puberty?

A

14 months male, 18 months female

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13
Q

What is the average age for caprine puberty?

A

6 months

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14
Q

What is the average age for canine puberty?

A

6-12 months average (breed and size affects age)

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15
Q

What is the average age for feline puberty?

A

5-9 months (freed and photoperiod affects age)

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16
Q

What is the average age for llama puberty?

A

2-4 years, don’t usually breed until 3 years

17
Q

What is onset of puberty NOT limited by?

A

Potential performance of gonads.

NOTE: prepubertal animals given exogenous GnRH will produce LH and FSH resulting in ovaries producing follicles and estradiol.

18
Q

What is the major limiting factor of puberty?

A

Failure of the hypothalamus to produce sufficient quantities of GnRH.

19
Q

What happens to the GnRH pulse frequency from the tonic center in the female after puberty?

A

Increases

20
Q

Where does the preovulatory GnRH surge come from?

A

The surge center

21
Q

Roughly how long does it take for the pulse frequency to raise to achieve puberty?

A

About 2 months

22
Q

Which hormone is low in the prepubertal female?

A

Estradiol

23
Q

What does the low estradiol in a prepubertal female cause?

A

No stimulation of the surge center, thus no preovulatory surge of GnRH and therefore LH

24
Q

How is the scretion of GnRH from the surge and tonic centers controlled?

A

Positive and negative feedback.

NOTE: Puberty will be initiated when GnRH neurons can respond completely to this feedback.

25
Q

What neurons are similar in number, function and distribution within the hypothalamus in males and females?

A

GnRH neurons

26
Q

What is the process by which a male reaches puberty?

A

Increased testosterone/estradiol gives negative feedback, then GnRH increases, LH and FSH increase.

27
Q

Before puberty, what is the surge center responding to?

A

The positive feedback that comes from estrogen.

28
Q

What hormone is low in the prepubertal female?

A

Estrogen

29
Q

What hormone has a positive feedback to the surge center, but negative feedback to the tonic center?

A

Estrogen

30
Q

What happens to the GnRH neurons in the tonic center?

A

Sensitivity goes down

31
Q

What 4 main things does the development of the hypothalamic nuclei depend on?

A

Body size/composition
Environmental cues
Social cues
Genetics

32
Q

What determines body size/composition?

A

Blood glucose and fatty acids.

NOTE: low levels = disruption of cycle

33
Q

What species might season of birth and photoperiod affect onset of puberty?

A

Sheep

NOTE: Sheep require decreasing day length

34
Q

What kind of social cues might affect onset of puberty?

A

Exposure to the male (eg. gilts exposed to a boar go through puberty sooner than sows in small and large groups).