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20 Cards in this Set
- Front
- Back
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what are the two centers in a mature female's hypothalamus that release GnRH?
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tonic centre
surge centre |
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what is secreted from the tonic centre and how ?
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spontaneous basal GnRH secretion in pulses of 1.5-2 hours.
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what is the function of the tonic centre?
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stimulates the pulsatile release of the gonadotrophins FSH and LH from the anterior pituitary.
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what does the surge centre release?
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low basal GnRH pulses until ESTROGEN reaches a critical threshold
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how does the surge centre respond to estrogen?
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responds with massive release of GnRH surge.
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what hormone is responsible for negative feedback on the surge and tonic centre's?
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progesterones.
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what effect does progesterone have on pulse frequency and amplitude in both centers?
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it lowers the pulse freq.
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what effect does progesterone have on the GnRH surge?
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it inhibits it.
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estrous cycles
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when reaching puberty, females enter a period of reproductive cyclicity characteriaed by series of predictible events, involving the ovaries, uterus, and behavior.
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puberty in females
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the process acquiring reproductive competence, i.e. being able to support pregnancy.
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what is onset of puberty in the female influenced by?
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genetic factors (breeds/age)
threshold body weight (fat depot) external factors e.g. photoperiod or social factors |
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hormonal changes during the estrous cycle go clinically unnoticed, except for a ?
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behavioral change, female is only willing to mate while in heat.
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what are the polyestrous species?
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cow, pig, human
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who has monoestrous?
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dog
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anestrus
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period without estrous cycles (silent period) caused by pregnancy, photoperiod, lactation, stress
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what is the length of a cycle in most animals?
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17-21 days
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what are the 2 phases in the estrous cycle?
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follicular phase (1/3 time)
luteal phase (2/3 time) |
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what are the phases in the follicular phase?
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proestrous and late phase= estrus
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what is the follicular phase dominated by?
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folliculogenesis with estrogen production
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what does estrogen lead to?
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sexual receptivity (estrus)
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