Exam 2 Flashcards
What are three definitions of puberty?
- The desire and ability to mate
- The process of acquiring reproductive competence
- Stage of development characterized by the onset of production and/or release of functional gametes
Differences in the hypothalamus of the male and female are established in _____ development.
Prenatal
What happens to the hypothalamus in the presence and absence of testosterone in development?
- Absence: Hypothalamus develops in a feminine way with a surge center and tonic center
- Presence: Hypothalamus is defeminized
How is he hypothalamus defeminized in the male?
Testosterone enters the brain and is converted to estrogen by aromatase
Why does the female hypothalamus not defeminize due to ovarian estrogen?
Alpha-fetoprotein binds specifically to circulating estrogen, making it too big to penetrate the blood-brain barrier. Testosterone is small and lipid-soluble, so it can penetrate the barrier.
What are the patterns of GnRH and LH secretion like in the postpubertal male?
Regular pulses of GnRH and LH every 2-6 hours in the male
What are patterns of GnRH and LH secretion like in the postpubertal female?
- Tonic center GnRH and LH released similar to the male, every 2-6 hours
- Big surge of GnRH and LH from the surge center once per cycle, every 28 days
What are the fundamental requirements for onset of puberty in males and females?
- As puberty approaches, GnRH pulses from the tonic center will increase, increasing the release of gonadotropins. Gonadotropins will stimulate the gonads to generate gametes and hormones such as estrogen and testosterone that will stimulate reproductive tissues and secondary sex characteristics.
What is limiting during the prepubertal period?
Before the onset of puberty, GnRH release from the tonic center occurs every few days. After puberty, it occurs every 2-6 hours. The major limiting factor i sthe failure of the tonic center of the hypothalamus to produce enough GnRH to stimulate elevated gonadotropin secretion.
Describe the gonadostat hypothesis. How does it affect the male and female?
Before puberty, low steroid levels have high negative feedback on the tonic center. As puberty approaches, the sensitivity to negative feedback decreases, so the pulses of GnRH increase, and LH and FSH increase.
- Female: Increased follicular development, leading to increased serum estrogen, leading to positive feedback at the surge center
- Male: Increased serum testosterone, increased sperm production
What are other factors that play a role in the onset of puberty?
- Stress
- Body Weight
- Genetics
- Social cues
- Pheromones
- Photoperiod in seasonal breeders
What do reproductive cycles, such as estrous or menstrual cycles, provide the female?
Multiple opportunities for pregnancy
What is anestrus? What times does this occur?
- Times when reproductive cycles cease
- Pregnancy
- Prior to puberty
- Menopause
- Stress
- Post-Partum
- Non-breeding season for seasonal breeders
- During lactation
Estrous is an _____, Estrus is a _____.
- Adjective
- Noun
The ____ ____ is the period between consecutive displays of estrus.
Estrous cycle
_____ is the display of sexual receptivity.
Estrus
What does it mean for a species to be polyestrus? What are some examples?
- Species that are capable of having estrous cycles throughout the year
- Cow, queen, pig, rodents
What does it mean for a species to be seasonally polyestrus?
-Species whose estrous cycles are limited to a certain season of the year
Long day breeders are ____ _____ species. Describe their cycles. Give some species examples.
- Seasonally polyestrus
- Begin to cycle in the spring, as the length of day increases
- Mare, hamster
Short-day breeders are ______ _____ species. Describe their cycles. Give some species examples.
- Seasonally polyestrus
- Begin to cycle in the fall as the day length decreases
- Ewe, doe, elk, nanny
What does it mean for a species to be monoestrus? What are some species examples?
- Species that have only one estrus per year
- Wolf, fox bear
- The domestic dog is also in this category, but could have 2-4 displays of estrus per year
What are the phases of the estrous cycle in farm species?
- Follicular Phase
- Luteal Phase
The follicular phase is the period from _____ ___ to ______. During the follicular phase, the dominant ovarian structures are the _____, the dominant ovarian hormone is _____, and the corpus luteum is ____ or _____.
- Luteal Regression
- Ovulation
- Follicles
- Estrogen
- Regressing
- Regressed
The luteal phase is the period from _____ to _____ ______. It is about ____% of the estrous cycle length in many species. During the luteal phase, the dominant ovarian strucutre is the ____ ____, and the primary ovarian hormone is _______.
- Ovulation
- Luteal Regression
- 80
- Corpus Luteum
- Progesterone
True or False: Antral follicular development occurs during the luteal phase and follicular phase in species with estrous cycles.
True
What are the stages of the estrous cycle in farm species?
- Proestrus
- Estrus
- Metestrus
- Diestrus
During _____, the corpus luteum is regressing. This causes a decline in ____ and increase in ____, supported by ____ and _____.
- Proestrus
- Progesterone
- Estrogen
- LH
- FSH
_____ is the most recognizable stage of the estrous cycle due to behavioral changes. ____ and _____ ___ are high, and the female permits ____.
- Estrus
- Estrogen
- Sexual Receptivity
- Copulation
Describe Metestrus. Circulating estrogen is _____ precipitously, circulating progesterone is _____ gradually, and ____ is occuring in the early part.
- The period between ovulation and the formation of a functioning corpus luteum
- Declining
- Increasing
- Luterinization
_____ is the longest stage of the estrous cycle. The ____ ____ is fully functional, and ____ production is high. What defines this period?
- Diestrus
- Corpus Luteum
- Progesterone
- The period from the onset of maximal serum progesterone to early luteolysis
What stages of the estrous cycle make up the follicular phase? The luteal phase?
- Follicular: Proestrus and estrus
- Luteal: Metestrus and diestrus
How many estrous cycles per year do wild canids display? Domestic bitches?
- one cycle per year
- around two
When does the estrous cycle occur in dogs?
February through May
What are the stages of the estrous cycle in the dog?
Anestrus, proestrus, estrus, diestrus
Describe anestrus in the dog.
Limited follicular development, will not achieve maximum estrogen, no estrous behavior or ovulation, low progesterone
During proestrus in the dog, ____ development progesses, and serum ____ gradually increases. What is unique to the dog in this stage?
- follicular
- estrogen
- Vaginal swelling and bloody vaginal discharge
In the dog, _____ begins shortly after the estrogen peak. Ovulation occurs ____ - ____ days after the LH surge, and fertilization will occur ____ - ____ hours after that.
- Estrus
- 2 to 3
- 48-72
True or False: Metestrus in the dog is characterized by declining estrogen and rising progesterone.
False, no designated metestrus in the dog because they are still showing estrous behavior during decreasing estrogen and rising progesterione
Describe diestrus in the dog.
It is the period of luteal function lasting 60 days. The length is the same whether the dog is pregnant or open.
What does it mean for the cat to be an induced/reflex ovulator?
Mating is required for a neural trigger to induce ovulation
What is the breeding season for cats?
For outdoor cats, it is January through September. It is longer for indoor cats due to increased light exposure.
In the absence of mating, the queen enters estrus every ___ days. Estrus lasts ____ days.
- 17
- 9
What two things occur during estrus of the cat?
- Sexual receptivity
2. Follicles capable of ovulating are present
What does stimulating of the vagina and cervix during mating lead to in the cat?
Reflex release of GnRH, LH surge, ovulation, and CL formation
What does the non-fertile mating of a reflex ovulator lead to?
Pseudopregnancy
_____ is a period of luteal function that is about half the length of a normal pregnancy. What is the evolutionary advantage to this system?
- Pseuopregnancy
- The induced ovulator comes back into heat sooner than CL function for the entire length of a normal pregnancy
What is gestational anestrus?
No signs of estrus or reproductive cycles during pregnancy
During gestational anestrus, what does progesterone do?
Progesterone has negative feedback on GnRH, decreasing LH and FSH, and decreasing follicular development and the absence of ovulation
True or False: A small percentage of cows and ewes will show estrus during pregnancy
True
What is the cause and evolutionary advantage of seasonal anestrus?
- Cause: Reduction in the frequency of GnRH pulses from the tonic center
- Advantage: Young are born when the weather is nicer
What occurs in the onset of seasonal cyclicity?
Frequency of GnRH pulses from the tonic center increase, LH and FSH increase, follicular development and ovulation
Why is the first ovulation after anestrus called a “silent ovulation”?
It is not accompanied by estrus behavior
What effect does photoperiod have on cyclicity?
As day length increases, excitation of retinal neurons increases leading to activation of inhibitory neurons, melatonin from the pineal gland decreases
Melatonin is secreted at ____.
Night
What happens to short day breeders during long days?
During long days, nights are short with low melatonin secretion. Low melatonin results in decreased frequency of GnRH pulses from the tonic center in short-day breeders.
What happens to long day breeders during long days?
During long days, nights are short with low melatonin secretion. Low melatonin results in increased frequency of GnRH pulses from the tonic center in long-day breeders.
Low melatonin causes ____ GnRH pulses in long-day breeders and ____ GnRH pulses in short day breeders.
- Increased
- Decreased