Puberty

Question 1

What increases in males when puberty begins?

Answer 1

sperm number
% motile sperm
% sperm with normal morphology

Question 2

What increases in females when puberty begins?

Answer 2

fertility increases sometime after the first ovulation

Question 3

What is puberty really?

Answer 3

a reactivation of the hypothalamo-pituitary-gonadal axis

Question 4

What happens during the juvenile state that is different from puberty?

Answer 4

the hypothalamo-pituitary-gonadal axis is held in check by suppression of GnRH secretion from the hypothalamus

Question 5

Developmental clock

Answer 5

times the genetic program for puberty and sets a lower age limit on its occurrence

Question 6

Permissive signals

Answer 6

• provide signals to the developmental clock that may delay puberty if they are limiting
• if signals are not limiting, they cannot advance puberty earlier than the genetically preset lowest age

Question 7

Where does the critical change for puberty occur?

Answer 7

hypothalamus; increase in frequency of GnRH pulses

Question 8

Direct drive hypothesis

Answer 8

steroid-independent increased drive for GnRH secretion

(glutamate is most important stimulant, GABA is most important inhibitory)
(is the initial event decline in inhibition or increase in stimulation?)

Question 9

Gonadostat hypothesis

Answer 9

secretin of GnRH during juvenile period is kept in check by negative feedback inhibition from gonadal steroids, but in puberty the sensitivity of the hypothalamus to the steroid feedback is changed

Question 10

Explain what happens in female puberty in regards to GnRH

Answer 10

hypothalamus sensitivity to steroid feedback decreases, GnRH secretion increases, pituitary increases FSH and LH release, and full follicular development in the ovaries can occur

Question 11

Initiation of puberty is most closely tied to what?

Answer 11

body growth rather than chronologic age

making the developmental clock wait until the permissive signals are achieved is a protective mechanism

Question 12

What happens if you restrict dietary intake

Answer 12

retards growth and delays the time of puberty

Question 13

How does photoperiod affect puberty?

Answer 13

seasonal breeders can only attain puberty within the breeding season

Question 14

The interaction of these two factors will determine whether puberty is achieved for those animals that follow photoperiods

Answer 14

1. growth rate

2. their time of birth in the previous spring

Question 15

How does time of birth affect puberty?

Answer 15

decides how much time they have to achieve the necessary target growth to initiate puberty

Question 16

How does growth rate affect puberty?

Answer 16

determines how long it takes to achieve the target growth to initiate puberty

Question 17

How do food supplies affect puberty?

Answer 17

seasonal variation in nutrition influence growth rate and thus the achievement of the metabolic gate

Question 18

Name some social factors in attainment of puberty?

Answer 18

pheromonal

tactile

Question 19

Vandenberg effect

Answer 19

hastening of puberty on exposure to males

Question 20

Explain how sex differences affect puberty

Answer 20

• there are sexually imprinted differences in the controls over GnRH secretion
• testosterone removes the strict requirement for photoperiod alternations and thus puberty can occur earlier in males

Question 21

What is anestrus?

Answer 21

absence of estrus or the absence of cyclicity

Question 22

Juvenile anestrus

Answer 22

prior to puberty the animal is acyclic

Question 23

Nutritional anestrus

Answer 23

in periods of nutritional stress and poor body condition, cyclicity ceases

Question 24

Seasonal anestrus

Answer 24

seasonal breeders will be anestrus in the non-breeding season

Question 25

Lactational anestrus

Answer 25

anestrus during lactation, varies between and within species

Question 26

Suckling anestrus

Answer 26

suppression of cyclicity relies on the daily frequency of suckling episodes by bonded offspring

Question 27

Milked anestrus

Answer 27

suppression of cyclicity relies on energy balance

Question 28

Explain hypothalamo-pituitary-ovarian physiology in the first two-thirds of pregnancy

Answer 28

progesterone is high and therefore the dominant follicles can’t go through final maturation and ovulation

Question 29

Explain hypothalamo-pituitary-ovarian physiology in late pregnancy

Answer 29

progesterone and estrogen levels are high, which suppress FSH so follicle waves no longer emerge and the ovary is quiescent

Question 30

Explain hypothalamo-pituitary-ovarian physiology after pregnancy

Answer 30

progesterone and estrogen levels fall, removing inhibitory feedback and FSH release occurs

Question 31

Why does suckling cause anestrus?

Answer 31

suckling of a bonded offspring causes release of maternal endogenous opioid peptides (EOPs) in the hypothalamus and these suppress GnRH neurons

Question 32

What factors influence the time it takes a dairy cow to have her first ovulation after calving?

Answer 32

• poor body condition and low voluntary intake
• BCS score
• low feed intake and catabolizing large amounts of body tissue
• increased feed intake in high producing cows (causes low circulation of estrogen)

Question 33

Improved energy balance results in what?

Answer 33

• central inhibition of GnRH is lifted, permitting increased LH
• increased insulin stimulates receptors for growth hormone on the liver and the somatotropic axis is restored
• dominant follicles can now fully mature and secrete sufficient estrogen to give an LH surge

Question 34

The first ovulation following improved energy balance will likely be what?

Answer 34

a silent heat

Question 35

Behavioral anestrus

Answer 35

social anestrus
seasonal anestrus
post-partum anestrus
juvenile anestrus

Question 36

What is senile anestrus?

Answer 36

when the number of primordial follicles falls below 1,000

Question 37

What is pathologic anestrus?

Answer 37

when various systemic disorders cause anestrus by suppression of the hypothalamo-pituitary axis