Puberty

Question 1

T/F: Males do not have a surge center.

Answer 1

True!

Question 2

What hormone “defeminizes” the hypothalamus in the male fetus thereby eliminating the GnRH surge center?

Answer 2

Estradiol that was converted from Testosterone

Question 3

What is attached to the estradiol produced by female fetuses that prevents it from crossing the BBB and therefore prevents the “defeminization” of the hypothalmus?

Answer 3

Alpha-fetoprotein

Question 4

What enzyme converts T4–>E2?

Answer 4

Acromatase

Question 5

T/F: Dairy cattle reach puberty later than beef cattle.

Answer 5

False!

Beef cattle hit puberty later than dairy cattle

Question 6

T/F: Onset of puberty is not limited by potential performance of the gonads or the pituitary.

Answer 6

True

Question 7

What is the major limiting factor for the onset of puberty?

Answer 7

Failure of the HYPOTHALAMUS to produce SUFFICIENT QUANTITIES of GnRH to cause gonadotropin release.

Question 8

How long does it take for LH pulse frequency to raise enough to achieve puberty?

Answer 8

~2 months

Question 9

Puberty will be initiated when _____ neurons can respond to the positive & negative feedbacks from the surge & tonic center.

Answer 9

GnRH

Question 10

Males only respond to ______ feed back by _________ because the decreased sensitivity of their GnRH neurons.

Answer 10

Negative feedback; Testosterone/Estradiol

Question 11

In females, what effects does estrogen have on the surge vs. tonic center?

Answer 11

Positive feedback–> Surge center

Negative feedback–> Tonic center

Question 12

What are the 4 main things development of hypothalamic nuclei(and therefore the onset of puberty) dependent on?

Answer 12

1. Threshold body size/composition
2. Exposure to enviromental cues
3. Exposure to social cues
4. Genetics(breed)

Question 13

In regaurds to body size/composition and it’s affect on puberty onset, what are the 3 main things found in blood that stimulate the GnRH neurons?

Answer 13

Leptin
Blood glucose
Blood fatty acids

Question 14

What enviormental cue do sheep require to reach puberty?

Answer 14

Decreasing day length

Therefore, spring born lambs reach puberty sooner(~6mo.) compared to fall born lambs(~12 mo.) since the fall lambs are born after the day length has already decreased and therefore must wait until the next fall to see the gradual decrease in day length.

Question 15

Exposure to what will cause accelerated puberty in sows?

Answer 15

Exposure to a boar