Podcast
Questions and Answers
At what age do foals begin to develop a pattern of melatonin secretion?
At what age do foals begin to develop a pattern of melatonin secretion?
Which gland is primarily responsible for controlling the release of gonadotrophins?
Which gland is primarily responsible for controlling the release of gonadotrophins?
What type of biological signals have a role in the hypothalamic-pituitary-ovarian axis?
What type of biological signals have a role in the hypothalamic-pituitary-ovarian axis?
Which of the following substances is responsible for the release of FSH and LH in vivo?
Which of the following substances is responsible for the release of FSH and LH in vivo?
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What is currently unknown regarding gonadotrophins?
What is currently unknown regarding gonadotrophins?
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Which substance, secreted by the hypothalamus, influences the release of pituitary hormones?
Which substance, secreted by the hypothalamus, influences the release of pituitary hormones?
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Which external factors can influence the hypothalamic-pituitary-ovarian axis?
Which external factors can influence the hypothalamic-pituitary-ovarian axis?
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What is the primary function of inhibin in the reproductive system?
What is the primary function of inhibin in the reproductive system?
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What was determined to be the molecular structure of porcine GnRH in 1971?
What was determined to be the molecular structure of porcine GnRH in 1971?
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Which hormone is primarily responsible for the day-to-day fluctuations in the reproductive cycle?
Which hormone is primarily responsible for the day-to-day fluctuations in the reproductive cycle?
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What specific role do activin and follistatin play in the context provided?
What specific role do activin and follistatin play in the context provided?
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Which hormone produced by the corpus luteum is mentioned as having a modulating effect on the release center?
Which hormone produced by the corpus luteum is mentioned as having a modulating effect on the release center?
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What effect does the preovulatory surge of oestradiol have on the anterior pituitary?
What effect does the preovulatory surge of oestradiol have on the anterior pituitary?
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What is the source of inhibin in the reproductive system?
What is the source of inhibin in the reproductive system?
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What happens to the response of the anterior pituitary to GnRH after the decline in progesterone levels?
What happens to the response of the anterior pituitary to GnRH after the decline in progesterone levels?
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Which hormone is mentioned as having a longer half-life compared to others in the hormonal feedback mechanism?
Which hormone is mentioned as having a longer half-life compared to others in the hormonal feedback mechanism?
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What is the primary factor responsible for luteal regression in species such as the ewe and cow?
What is the primary factor responsible for luteal regression in species such as the ewe and cow?
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Where is PGF2α primarily synthesized in mammals?
Where is PGF2α primarily synthesized in mammals?
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What characterizes the cyclic activity of mares compared to other equine species?
What characterizes the cyclic activity of mares compared to other equine species?
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Which of the following describes the process of functional regression of the corpus luteum?
Which of the following describes the process of functional regression of the corpus luteum?
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What is the typical reproductive behavior of native pony breed mares?
What is the typical reproductive behavior of native pony breed mares?
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What effect can environmental conditions have on mare reproductive cycles?
What effect can environmental conditions have on mare reproductive cycles?
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In regards to luteal regression, what does the term 'structural regression' refer to?
In regards to luteal regression, what does the term 'structural regression' refer to?
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What is the significance of PGF2α having been first isolated from semen?
What is the significance of PGF2α having been first isolated from semen?
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What role does noradrenaline play in ovarian cyclicity?
What role does noradrenaline play in ovarian cyclicity?
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How does serotonin affect LH secretion?
How does serotonin affect LH secretion?
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What occurs when the conversion of dopamine to noradrenaline is inhibited?
What occurs when the conversion of dopamine to noradrenaline is inhibited?
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Which system contributes to the secretion of FSH and LH in domestic species?
Which system contributes to the secretion of FSH and LH in domestic species?
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What hormone's release is primarily regulated by dopamine?
What hormone's release is primarily regulated by dopamine?
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Which hormone is responsible for the 'oestradiol-induced' release of LH?
Which hormone is responsible for the 'oestradiol-induced' release of LH?
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What effect does the inhibition of serotonin have on ovarian cyclicity?
What effect does the inhibition of serotonin have on ovarian cyclicity?
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Where is GnRH secreted in the context of ovarian cyclicity regulation?
Where is GnRH secreted in the context of ovarian cyclicity regulation?
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What is the approximate maximum size of the larger ovary in heifers and young cows?
What is the approximate maximum size of the larger ovary in heifers and young cows?
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Which characteristic describes the smaller ovary?
Which characteristic describes the smaller ovary?
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During what phase will there be little variation in ovarian size due to the bulk of the developing corpus luteum (CL)?
During what phase will there be little variation in ovarian size due to the bulk of the developing corpus luteum (CL)?
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What is a notable feature of the larger ovary during examinations of heifers and young cows?
What is a notable feature of the larger ovary during examinations of heifers and young cows?
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What dimensions characterize the smaller ovary?
What dimensions characterize the smaller ovary?
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When will the corpus luteum start to significantly influence the size of the ovary?
When will the corpus luteum start to significantly influence the size of the ovary?
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What is the primary reason for the little size difference observed during oestrus?
What is the primary reason for the little size difference observed during oestrus?
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What measurement represents the dimensions of the larger ovary from side to side?
What measurement represents the dimensions of the larger ovary from side to side?
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Study Notes
Hormonal Regulation of Reproduction
- Inhibin produced by antral follicles impacts the hypothalamus and anterior pituitary.
- Oestradiol from maturing follicles and progesterone from the corpus luteum provide negative feedback for hormonal regulation.
- Episodic and tonic releases from the hypothalamus are adjusted by oestradiol and progesterone levels.
- Low progesterone levels play a modulating role in the hypothalamic release center, particularly in ruminants.
Peptide Hormones' Role
- Activin stimulates FSH secretion, while follistatin suppresses it; both are isolated from ovarian follicular fluid.
- The exact roles of activin and follistatin in follicular growth control remain unclear in domestic species.
Gonadotropin Release Mechanism
- Inhibin, released by granulosa cells of large antral follicles, regulates the anterior pituitary's response to GnRH, influencing ovulation and corpus luteum formation.
- High oestradiol levels trigger the preovulatory surge of LH necessary for ovulation.
Seasonal Reproduction Control
- The pineal gland assists in regulating reproduction in seasonal breeders, affecting puberty timing and gonadotropin release via melatonin.
- Seasonal breeders, like mares, display cyclic activity primarily in spring to autumn, becoming anoestrous during winter.
Ovarian Size and Luteal Changes
- Functional luteal regression occurs rapidly, leading to a swift decline in progesterone levels.
- Structural regression of the corpus luteum is slower, impacting ovarian size changes over time.
Follicular Dynamics in Ovaries
- Ovarian size difference is notable in heifers and young cows; one ovary typically larger than the other (larger: ~3.5cm; smaller: ~2.5cm).
- Limited size variation occurs during the interoestrus phase due to the developing or regressing corpus luteum.
Neurotransmitter and Hormonal Interactions
- Noradrenaline facilitates FSH and LH release, while dopamine inhibits LH release.
- Serotonin suppresses basal LH secretion, and dopaminergic regulation is crucial for prolactin control.
Anatomic and Physiological Considerations
- GnRH, released from the hypothalamus, drives FSH and LH secretion in the anterior pituitary.
- PGF2α, a luteolysin, exhibits activity across multiple species in luteal regression processes.
Impact of External Factors
- External stimuli such as light and touch affect the hormonal release mechanisms tied to the hypothalamic-pituitary-ovarian axis.
- Increased food intake and artificial lighting can enhance cyclic activity in seasonal breeders during unfavorable conditions.
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Description
This quiz focuses on the role of inhibin and oestradiol in the regulation of the hypothalamus and anterior pituitary. It covers the feedback mechanisms and the effects of progesterone produced by the corpus luteum. Test your understanding of these vital hormones in the reproductive system.
