Exam 2 Flashcards
Alpha fetal protein is found in the blood of both male and female fetuses and binds tightly to estradiol, preventing it from crossing the blood-brain-barrier in female fetuses and inactivating the GnRH surge center in the hypothalamus
T
External factors such as stress can modulate the function of presynaptic neurons in the hypothalamus which can reduce the secretion of GnRH from neurosecretory cells in the tonic release center
T
In the female, the onset of puberty is a result of a progressive decrease in hypothalamic sensitivity (tonic GnRH release center) to the negative feedback effects of estradiol
T
In the prepubertal female, the GnRH surge center of the hypothalamus is unable to stimulate a preovulatory surge release of LH from the anterior pituitary due to the lack of preovulatory size follicles on the ovaries
T
There is evidence that the initiation of high frequency low amplitute GnRH pulses can be advanced by exposure to increased glucose and/or fatty acids concentrations in the blood
T
The anterior pituitary of a prepubertal female is unable to secrete significant amounts of FSH and LH even if stimulated by exogenous GnRH
F
Circulating Leptin is directly related to body fatness and may function to inform the GnRH secreting neurons of the nutritional status of the female
T
Fall (September- October) born lambs receiving adequate nutrition reach puberty 5-6 months, while spring born lambs reach puberty at 10-12 months
F
Prepubertal gilts housed in larger groups (>10 gilts) exhibit delayed puberty while prepubertal gilts housed in small groups (2-3 gilts) reach puberty at the expected time
F
Presence of a male will reduce age at puberty in prepubertal gilts or heifers
T
In the sheep, low melatonin produced by the pineal gland during the spring and summer results in low kisspeptin secretion resulting in reduced GnRH secretion by the tonic release center of the hypothalamus, resulting in anestrus
F
In the beef cow, 3 or more suckling bouts by her offspring per day are required to keep blood LH low and to maintain lactational anestrus
T
The follicular phase in the women occupies only 20% of the length of the menstrual cycle, while in the cow it only occupies 50%of estrous cycle length
F
Lactating women on a high plane of nutrition return to cyclicity sooner postpartum than lactating woman on a low plane of nutrition
T
In the postpartum rabbit, prolactin is no longer released in response to suckling after 30 days of lactation, and the mother leaves her offspring at that time to fend for themselves
T
Exhibits clusters of estrous cycles during the spring and summer only
seasonally polyestrus (long day breeder) mare
uniform distribution of estrous cycles throughout the year
polyestrus
pig
exhibits one estrous cycle per year
monoestrus
wolf
exhibits clusters of estrous cycles during the fall and winter only
seasonally polyestrus (short day breeder) sheep
An implant containing melatonin during anestrus will initiate early cyclicity in this specie
sheep
An implant containing a melatonin antagonist during anestrus will initiate early cyclicity in this specie
mare
Regu-mate (altrenogest) is a progesterone that was developed as a estrous synchronizing agent in these 2 species
mare
pig
increases collegians activity by theca internal cells (degrades tunica albuginea forming stigma)
progesterone
increased follicular blood flow and fluid uptake
prostaglandin E2 (PGE2) and histamine
increases contraction of ovarian smooth muscle and releases lysosomal enzymes from the granulose cells to further weaken the follicular wall for oocyte expulsion
prostaglandin F2a
Plasminogen
dissolves the blood clot in the CH and remodels the follicle into a CL
Specific cellular events that are initiated when LH bind to its membrane receptors on luteal cells and ends with the secretion of progesterone
1) Cholesterol is delivered to the luteal cells from the blood
- internalized by cell
2) LH binds to receptors on plasma membrane of luteal cells
3) LH receptor complex activates a G protein, which in turn activates “AC” which converts ATP to cAMP
4) cAMP activates kinase enzymes –>promote cellular cholesterol uptake and empty to mitochondria
5) mitochondria enzyemes convert cholesterol to pregenelone
6) Pregenelone are then converted to progesterone
At the end of lactational anestrus in the cow or seasonal anestrus in the sheep, why is the first ovulation not accompanied by estrous behavior
Silent Ovulation occurs because in order for max expression of behavioral estrus, progesterone must be present for a certain period of time prior to exposure to estradiol. In other words, progesterone from the first postpartum CL formed after the first ovulation and after seasonal anestrus “primes” the brain so that its sensitivity to estradiol is optimized.
What is specific reason why women menstruate (suffer endometrial loss) and livestock species do not? Be specific about the hormonal changes involved and their impact on the endometrium
Women suffer endometrial loss while livestock species do not because the CL of women secrete estradiol and progesterone and when those hormones drop the endometrium sluffs. Estradiol thickens the endometrium, increases blood flow, and promotes “valve growth”, while progesterone makes the endometrium secrete uterine milk
removal of the uterus will prolong the lifespan of the CL
pig
sheep
cow
mare
removal of the uterus will not affect the lifespan of the CL
dog
humans
species which deliver PGF2a locally from the ipsilateral (adjacent) uterine horn to the ovary by way of transfer from the uterine vein to the ovarian artery
Sheep
Pig
Cow
specie in which ovarian PGF2a kills the CL
Humans
in these species PGF2a receptors appear on luteal cells after day 6 of the estrous cycle, thus exogenous PGF2a is ineffective in inducing luteolysis prior to that time
Mare
Cow
Sheep
Specie in which PGF2a has no effect on luteal function
Dog
Specie in which PGF2a receptors do not appear on luteal cells until day 14-16 when the CL is already dying thus exogenous PGF2a is ineffective in shortening CL lifespan
Pig
induces thickening and cornification of the vestibule
estradiol
increases the secretion of uterine gland
progesterone
increases uterine gland growth
estradiol
reduces uterine motility and allows implantation
progesterone
promotes genital swelling
estradiol
increases blood flow to the reproductive tract
estradiol
exerts a negative feedback to inhibit GnRH secretion and reductions of GnRH receptors on pituitary gonadotrophs reducing FSH and LH secretion
progesterone
increases the infiltration of white blood cells into the uterus
estradiol
day 1-6
CL unaffected
days 15-20
day 7-17
all CL killed in 3 days
day 11
day 18-21
CL die normally over the net 3 days
days 11-14
stimulates the leydig cells to produce testosterone
LH
natural male hormone that exerts a negative feedback on GnRH secretion from the tonic release center of the hypothalamus *don’t need this test
testosterone
man made hormone administered to promote muscle growth and performance *don’t need this test
anabolic steroid
stimulates androgen binding protein production by stroll cells *don’t need this test
FSH
inhibits FSH secretion by the anterior pituitary gonadotrophs *don’t need this test
inhibin
This hormone binds to receptors on sertoli cells and maintains spermatogenesis at an optimal level *don’t need this test
FSH
This hormone stimulates sex drive and maintenance of the male genital duct system and through conversion to DHT promotes a male phenotype *don’t need this test
testosterone
When administered in high doses over a prolonged period it will kill the leydig cells resulting in sterility *don’t need this test
anabolic steroid
forms the postnuclear cap *don’t need this test
manchette
forms proacrosomal granules *don’t need this test
golgi saccules
gives rise to the attachment site for the sperm tail *don’t need this test
proximal centriole
gives rise to the axoneme *don’t need this test
distal centriole
spiral around the middle piece of the sperm tail *don’t need this test
mitochondria
provide stability to the sperm tail *don’t need this test
nine coarse outer fibers
from the cap of the sperm head and contains hydrolytic enzymes *don’t need this test
acrosome
Requirements of a good semen extender used for artificial insemination *don’t need this test
1) minimize cold shock
2) prevent microbial growth
3) maintain viability
4) low in cost
5) be isotonic
6) be a good buffer
7) provide nutrients
