Exam 2 Animal Reproduction

What is puberty?

The ability to reproduce successfully

What are the three components of the "Great Awakening"?

Gamate production, endocrine changes, behavioral changes

When do mice reach puberty?

1.5 months

When do sheep reach puberty?

7 months

When do cattle reach puberty?

11 months

When do cetaceans reach puberty?

12 months

When do horses reach puberty?

14 months

When do elephants reach puberty?

21 months

Why is age at first heat not a good measure of puberty in females?

First ovulation usually not accompanied by estrus

Why is age at first ovulation not a good measure of puberty?

Difficult or time comsuming to determine

What is the best way to define puberty in a female?

Age when the body is able to support the high "metabolic cost" of pregnancy/lactation

What are insufficent ways of determining puberty in males?

Age when sexual behaviors are expressed and age at first ejaculation

What is the best way to determine puberty in males?

When a threshold of sperm is reached in a sample of ejaculate AND the horse is fully grown

What is the limiting factor in the onset of puberty?

The hypothalamus (surge and tonic centers)

The female hypothalamus contains...

Surge center and tonic center

The male hypothalamus contains...

Tonic center only

What "defeminizes" the male brain?

Testosterone converted into estradiol

How does estradiol cause defeminization of the brain?

E2 causes cell death of AVPV kisspeptin neurons

What prevents estrogen from defeminizing the female brain?

Alpha-fetoprotein

What do KNDY neurons do?

Work as a part of the GnRH pulse generator to release GnRH in a pulsitle fashion

After puberty, what is the pattern of GnRH pulses in the surge center?

High amplitude
Low frequency

After puberty, what is the pattern of GnRH pulses in the tonic center?

Low amplitude
High frequency

In the prepubertal female, the tonic center is more sensitive to what?

P4/E2 negative feedback

The prepubertal female lacks insufficent levels of what hormone to stimulate the surge center?

E2

As the prepubertal female matures, what happens to the hypothalamus?

Becomes more sensative to E2 positive feedback and AVPV kisspeptin neurons mature

What is the pattern of tonic LH release in postpubertal females?

Low amplitude, high frequency, surge occuring after an E2 surge

What is menarche?

Age of first menstruation

What are the Tanner Stages?

Levels of secongary sex characteristics

What caused a decrease in the age of menarche since 1900's?

Genetics/ethnicity, nutrition, and environmental factors

What is the minimum percentage of fat necessary for menarche?

17%

In a very young animal, energy is directed towards...

Body maintenance and vital functions

In the juvenile, what happens to the use of energy?

Metabolic rate decreases and fat storage increases, allowing for energy to be available for non-vital functions

Which metabolic factors affect GnRH neuron activity?

Blood glucose, free fatty acids, and leptin

What do adipocytes release?

Leptin

In seasonal breeders, puberty onset is controlled by...

Season of birth, photoperiod, and body size/weight

Short day breeding species enter puberty in the...

Fall

Long day breeding specient enter puberty in the...

Spring

What is the Whitten effect?

When the presence of a male accelerates puberty in gilts, heifers, and mice

What are the benefits of shortening the onset of puberty in males?

Earlier sperm production, smaller generational interval, speeds genetic improvement

What does heat ensure?

Mating around the time of ovulation

Sexual receptivity/copulation occurs...

1st half of the cycle before ovulation

If no conception occurs...

Another estrous cycle begins

If conception occurs...

A periods of anestrous occurs and estrous cycle cease

Polyestrus breeds cycle...

Regularly during the year

Seasonal polyestous breeds cycle...

In clusters seasonally

What are examples of short day breeders?

Sheep, goats

What are examples of long day breeders?

Mare

Monoestrous breeds cycle..

Once per year

Dogs cycle...

3 times every 2 years

What are the 2 phases of the estrous cycle?

Follicular phase and luteal phase

The luteal phase takes up what percentage of the estrous cycle?

80%

The follicular phase takes up what percentage of the estrous cycle?

20%

The folliuclar phase begins with \_______ and ends with \_______.

Corpus luteum regression, ovulation

What type of follicle dominates the ovary during the follicular phase?

Antral follicle

The luteal phase begins with \______ and end with \_________.

Ovulation, corpus luteum regression

What is the main hormone during the luteal phase?

Progesterone

What type of follicle dominates the ovary during the luteal phase?

Corpus luteum

What are the 4 stages of the estrous cycle?

Proestrus, estrus, metestrus, diestrus

What 2 stages of the estrous cycle are the luteal phase?

Metestrus and diestrus

What 2 stages of the estrous cycle are the follicular phase?

Proestrus and estrus

During proestrus, what hormone decreases and what hormone increases?

P4 decreases, E2 increases

How long does proestrus last in most species?

2-5 days

During estrus, what behaviors are exhibited?

Proceptive and receptive behaviors

During metestrus, what happens to the ruptured follicle?

It differentiates or lutenizes to form the corpus luteum

During diestrus, what hormone is high in concentration and what hormone is low?

P4 is high, E2 is low

How long does diestrus typically last?

10-14 days

What event marks the end of diestrus?

Luteolysis

The rodent estrous cycle lacks which phase?

Metestrus

During anestrus ovaries are

Inactive, no ovulatory follicles and no corpus luteum

What hormonal changes cause anestrus?

Low GnRH, FSH and LH

What can cause anestrus?

Pregnancy, lactation, season, poor nutrition, stress, or pathology

What is gestational anestrus?

Lack of estrous cycle due to high P4 from the corpus luteum, which inhibits GnRH and therefore no increase in LH/FSH, suppressing follicle growth/ovulation during pregnancy

What is the purpose of anestrus following delivery?

Time for uterine repair and protection from copulation introduced infections

What is lactational anestrus?

Prevents a new pregnancy before young are weaned

What is seasonal anestrus?

Lack of estrus during seasons when embryo/neonate survival is not favored

Long day breeders breed during the \______ and have anestrus during the \______.

Spring, winter

Typically how long is the gestational period for long day breeders?

1 year

Short day breeders cycle during the \_______ and have anestrus during the \_________.

Fall, summer

In long day breeders, as RFRP-3 increases, kisspeptin neurons are...

Stimulated, resulting in an increase in GnRH and LH/FSH, resulting in cyclicity

In short day breeders, as RFRP-3 increases, kisspeptin neurons are...

Inhibited, resulting in a decrease in GnRH and FSH/LH, causing no cycle

After light hits the eye, what happens?

The signal travels to the suprachiasmatic nucleus, which then transmits the signal to the superior cervical ganglion, which then goes to the pineal gland that causes a low melatonin release, triggering RFRP neurons to fire, resulting in an increase in RFRP-3

What is silent estrus?

Ovluation without behavioral estrus

What causes silent estrus to occur?

Lack of P4 to prime the brain before estrus occurs and lack of sensitivity to E2

In induced ovulators, if there is no copulation...

"Postestrus" occurs, there is no ovulation, therefore no corpus luteum and no luteal phase (metestus and diestrus)

During proestrus of a dog, what happens physically?

Vaginal swelling and blood tinged discharge

How long does diestus last in a dog?

2 months

How long does anestrus last in dogs?

5 months

Day 0 of the estrous cycle refers to...

The start of estrus

What is the anti-pathogen hypothesis?

The idea that the purpose of menstruation is to remove sperm-borne pathogens to prevent infection

What is the conservation of energy hypothesis?

The idea that cyclical regression/renewal is energetically less costly than maintaining the state needed for implantation

What is the coevolution of the embryo and endometrium hypothesis?

The idea that menstruation is a result of the immune battle between the embryo and endometrium

What is Seasonale?

Extended birth control pills and menstrual suppression (4 periods per year)

How does Seasonale work?

Synthetic steriods decrease ovulation and endometrial growth

What are the benefits of menstrual suppression?

Relief from menstrual pain, convenience (less blood loss, risk of anemia, risk of ovarian cancer)

What are the risks of menstrual suppression?

Short term:
- blood clots, stroke, heart attack
Long term:
- unknown (future fertility, effects on other organs)

What are the 4 major events during the follicular phase?

Increased gonadotropin release, follicular growth, sexual receptivity, ovulation

Which hormone has positive feedback on the surge center?

E2

What hormone has negative feedback on FSH

E2 and inhibin

What hormone has negative feedback on GnRH release from the surge and tonic centers?

P4

What does basal secretion of GnRH cause?

FSH and LH release, follicular growth