exam 2 Flashcards
Neuroendocrinology
Interaction between nervous system and endocrine glands
what do neuron produce
impulses
what do neuroendocrine cells produce
neurohormones
what do endocrine cells produce
hormones
what is the blood supply between the hypothalamus and AP
hypothalamo-hypophyseal portal system
function of GnRH
causes release of FSH and LH
what is GnRH used for
treatment of cystic ovaries, prepubertal and anestrous animals to being cycles
Trade name for GnRH
Cystorelin
function of prolactin-releasing factor (PRH or PRF)
releases prolactin from AP
function of prolactin inhibiting factor ( PIF) aka dopamine
inhibits prolactin release from AP
function of corticotropin-releasing hormone (CRH)
stimulates release of ACTH from AP
neuroHormones that affect Posterior pituitary
Oxytocin
site of production of oxytocin (OT)
paraventricular and supraoptic nuclei cells of the hypothalamus, CL of cow, ewe, and human
Where is oxytocin stored
Posterior Pituitary
what are supraoptic paraventricular nuclei
body of nerve cells in hypothalamus in relation to PP
functions of Oxytocin
milk let down, stimulates uterine contractions during sperm and egg transport and parturition, may play a role in CL function (luteolytic in cow, ewe, and goat)
what enhances responsiveness of smooth muscle to OT
estrogen
uses of OT
induces milk let down, the expulsion of retained placenta, aids delivery of young when labor is extended
what is a negative feedback
one hormone inhibits release of another hormone
examples of negative feedback
-Increasing concentrations of progesterone, estrogen, or testosterone inhibits the release of GnRH, FSH, and LH
-Increasing concentrations of inhibin inhibits FSH from AP
what is positive feedback
where one hormone stimulates the release of another
example of Positive feedback
increasing concentrations of estrogen stimulate release of GnRH, LH, FSH, and Prolactin
condition of being first capable of reproducing
puberty
what does puberty mean for the male
ability to copulate and ejaculate mature spermatozoa
what does puberty mean for the female
onset of regular estrous cycles with ovulation of female gametes
condition of producing the maximum number of gametes
sexual maturity
genetic factors that affect age at puberty
body weight and nutrition (BCS and growth)
environmental factors that affect age at puberty
photoperiod, temperature, and social factors
progressive accomplishment of alterations in genital tract; characteristic of estrus, metestrus, diestrus and proestrus produced by changes in ovarian hormones
estrous (period from beginning of estrus to beginning of next estrus)
where does estrous occur
non-primate females
period of sexual receptivity in females also called “heat”
estrus
estrous
adjective- cycle as a whole
estrus
noun- specific phase
days of proestrus
17-21
what happens during proestrus
ovarian follicles are growing rapidly, increase in estrogen from growing follicles, decrease in progesterone from CL, mucosal layers of vagina and uterus multiply
days of estrus
1
what happens during estrus
period of sexual receptivity, surges of FSH and LH from AP, sow, ewe, and mare ovulate
days of metestrus
2-4
what happens during metestrus
cow ovulates, beginning of luteal phase, short trasitional phase after ovulation with decreasing estrogen and increasing progesterone, recently ruptured follicle in reorganizing into CL
what happens during metestrus
cow ovulates, beginning of luteal phase, short transitional phase after ovulation with decreasing estrogen and increasing progesterone, recently ruptured follicle in reorganizing into CL
days of diestrus
5-16
what happens during diestrus
continuation of luteal phase in species with long estrous cycles (absent in animals with short cycles) , CL becomes fully developed and progesterone exerts a dominant influence on oviducts, uterus, vagina, pituitary, and hypothalamus, CL remains functional for about 13 days in ewe and 15-17 days in sow cow and mare, CL regresses at the end of diestrus
anestrous
period between diestrus and proestrus in monoestrous and seasonal polyestrous animals. characterized by quiescence of repro tract
when is anestrous
nonbreeding season of ewe and mare varies in length, ends when proestrus begins
when is anestrous
nonbreeding season of ewe and mare varies in length, and ends when proestrus begins
two phases of the menstrual cycle
luteal and follicular
how long is each phase and what separates them
2 weeks, ovulation
occurs in rabbits and other induced ovulators, LH release is induced by mating, ovulation occurs every 8-12 hrs after mating
continuous estrous
Occurs in bears, wolves, foxes, and some dogs, only one estrous cycle per year, long anestrous separates each cycle
monoestrous
true polyestrous cycles, 2 or more estrous cycles per year unless interrupted by pregnancy, composed of proestrus, estrus, metestrus, and diestrus merging into proestrus
polyestrous
difference between seasonal polyestrous and polyestrous
last diestrus of breeding season would proceed into anestrous ( ewe and mare)
mechanism
- retina of the eye is a sensor for light signals
-impulses travel by way of the optic nerve to the pineal gland
-pineal gland relases melatonin
-melatonin serves as a mediator between photoreceptors, hypothalamus and/or AP
-episodic surges of LH occur as breeding season begins
how long are short estrous cycles
4-6 days
what animals have short cycles
rat, mouse, hamster, and gerbil
what happens if mating does not occur? and if sterile mating occurs.
becomes follicular cycles. if sterile mating occurs, pseudopregnancy begins and lasts about 2 weeks
what is needed to induce functional activity of CL ( progesterone secretion)
mating
how long are long estrous cycels
15-16 days or longer
animals with long cycles
cow, ewe, sow, mare, and guinea pig
does not require mating to produce functional CL, sterile mating does not shorten or lengthen cycle
long estrous cycles
two phases of long estrous cycles
follicular ( proestrus and estrus; follicles growing and estrogenic phase) and luteal (metestrus and diestrus; secretory phase of CL, progestational phase)
estrus that occurs within a few days after parturition, rarely observed in ewes and cows
post-partum estrus
post-partum estrus in sow
occurs every 3-10 days after farrowing, ovulation rarely occurs, non-fertile estrus
post-partum estrus in mare
called foal heat, begins 5-15 days after foaling and lasts 1-10 days, mare usually ovulates but fertility may be lowered if abnormal tract exists
absence of psychological behavior of estrus, occurs in all farm animals, ovulation occurs
silent estrus or quiet ovulation
initial estrus interrupted by a period of non-receptivity followed by another period of estrus, frequently seen in mares and occasionally in cows
split estrus
estrus without ovulation, occurs in all farm animals, best example is postpartum estrus in sows
anovulatory estrus
the continuous psychological desire to mate, ovulation rarely occurs, most common in cows, less common in mares, rare in ewe or sow, cystic ovaries usually accompany nymphomaniac condition
nymphomania
spontaneous ovulation
repeated ovulation at regular intervals except during pregnancy, LH release is cyclic and independent of mating stimulus, LH release is triggered by increasing concentrations of estrogen
what animals have spontaneous ovulation
cow, ewe, sow, mare, rat, hamster and guinea pig
induced ovulation
ovulation occurs after stimulation of vagina and/or cervix, LH release only after mating stimulus, estrus persists for a variable length of time
what animals have induced ovulation
rabbit, cat, mink, and llama
what hormone does the hypothalamus secrete into blood vessels connecting to the AP
GnRH
what does GnRH release from the AP
FSH and LH
where does FSH go once secreted
circulation, transported to ovary and stimulates follicular developement (granulosa cells to produce estrogen)
where does LH go once secreted
circulation and acts synergistically with FSH to stimulate secretion of estrogen by follicle
what are peak concentrations of LH and FSH responsible for
estrogen, which has positive and negative feedback on the hypothalamus and AP to control release of FSH and LH
what else are the peak concentrations responsible for
rupture of follicle and release of ovum (ovulation)
what does LH do after ovulation
transforms the follicle into a CL which secretes progesterone ( stimulated by LH)
what kind of feedback does progesterone have on the hypothalamus and AP
negative feedback; to decrease FSH and LH secretion
when do follicles grow
at all times of the cycle
what happens to the granulosa and theca cells during the cycle
granulosa cells increase in numbers and layers of theca cells grow and encompass periphery of follicle
two types of theca cells
theca externa and theca interna
theca externa
connective tissue surrounding entire follicle
theca interna
inner layer of thecal cells next to the basement membrane
what do the theca intera do
synthesize androgens (T) under influence of LH
what happens to the androgens once they are produced
pass across the basement membrane to granulosa cells where they are converted to estrogen under influence of FSH
what happens to follicles right before estrus
undergo rapid maturation
what happens to estrogen during the follicular phase
increases
when is the concentration of estrogen the highest
beginning of estrus
when does estrous behavior occur
follicular phase
what is estrus a result of
local effect of estrogen on central nervous system
relationship between progesterone and estrogen
progesterone has a synergistic action with estrogen in inducing sexual receptivity
feedback of increasing estrogen on hypothalamo-hypophyseal axis
positive feedback; causes surge of LH and FSH during estrus
what does LH do during estrus
activates enzymes that digest connective tissue in wall of follicle, resulting in ovulation
when does ovulation occur in most domestic animals
after LH peak
what happens during the luteal phase
- granulosa and theca cells differentiate into luteal cells
- CL secretes progesterone under influence of LH (luteotropic effect)
when does CL reach maximum function and size
mid-luteal phase
what causes CL regression
increased concentrations of prostaglandin (produced by endometrium during late luteal phase)
mechanism of CL regression in ewe and cow
- mid to late diestrus: non-ovulatory follicles secrete increasing concentrations of estrogen
- endometrial cells stimulated by estrogen to synthesize oxytocin receptors
- oxytocin from CL (or PP) binds to OT receptors and stimulates the secretion of arachidonic acid and prostaglandin synthetase by endometrium
- arachidonic acid converted by prostaglandin synthetase to prostaglandin
- prostaglandin secreted into uterine veins and lyses the CL
