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Questions and Answers
What is the primary function of the episodic/tonic system?
What is the primary function of the episodic/tonic system?
Which hormone is primarily responsible for inducing ovulation in certain species?
Which hormone is primarily responsible for inducing ovulation in certain species?
In which animals is ovulation not spontaneous and induced during copulation?
In which animals is ovulation not spontaneous and induced during copulation?
Which factor is involved in suppressing FSH secretion?
Which factor is involved in suppressing FSH secretion?
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Which component directly stimulates ovarian functions such as folliculogenesis?
Which component directly stimulates ovarian functions such as folliculogenesis?
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What initiates the neuro-endocrine reflex leading to the activation of GnRH neurons?
What initiates the neuro-endocrine reflex leading to the activation of GnRH neurons?
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What is the result of the activation of GnRH neurons in the surge center?
What is the result of the activation of GnRH neurons in the surge center?
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What role does the anterior pituitary play related to the ovaries?
What role does the anterior pituitary play related to the ovaries?
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What role does dopamine play in the secretion of prolactin?
What role does dopamine play in the secretion of prolactin?
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Which cells primarily form the corpus luteum after ovulation?
Which cells primarily form the corpus luteum after ovulation?
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What substance is believed to inhibit prolactin secretion?
What substance is believed to inhibit prolactin secretion?
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How does the administration of exogenous opioid peptides affect FSH and LH secretion?
How does the administration of exogenous opioid peptides affect FSH and LH secretion?
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What change occurs in the corpus luteum's mass after ovulation in the ewe?
What change occurs in the corpus luteum's mass after ovulation in the ewe?
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What happens to gonadotrophin concentrations when naloxone is infused?
What happens to gonadotrophin concentrations when naloxone is infused?
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Which cell types comprise the largest percentage of the corpus luteum in the ewe?
Which cell types comprise the largest percentage of the corpus luteum in the ewe?
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What type of activity have endogenous peptides like β-endorphin and met-enkephalin been found to exhibit?
What type of activity have endogenous peptides like β-endorphin and met-enkephalin been found to exhibit?
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What is the role of FSH in the normal oestrous cycle?
What is the role of FSH in the normal oestrous cycle?
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What is observed about the corpus luteum after 48 hours post-ovulation?
What is observed about the corpus luteum after 48 hours post-ovulation?
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What is likely responsible for the dominance of one follicle over others?
What is likely responsible for the dominance of one follicle over others?
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What is the typical size range for large follicles during dioestrus?
What is the typical size range for large follicles during dioestrus?
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What is a characteristic of the corpus luteum by the seventh to eighth day of dioestrus?
What is a characteristic of the corpus luteum by the seventh to eighth day of dioestrus?
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What effect does the presence of large follicles during dioestrus have on the ovaries?
What effect does the presence of large follicles during dioestrus have on the ovaries?
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How does the corpus luteum feel upon palpation 48 hours after ovulation?
How does the corpus luteum feel upon palpation 48 hours after ovulation?
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What kind of cells contribute to the development of the corpus luteum?
What kind of cells contribute to the development of the corpus luteum?
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What color is the active corpus luteum just after ovulation in a nulliparous heifer?
What color is the active corpus luteum just after ovulation in a nulliparous heifer?
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What indicates the regression of a corpus luteum?
What indicates the regression of a corpus luteum?
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How does the size of an ovary change during oestrus?
How does the size of an ovary change during oestrus?
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Which stage shows the corpus albicans formed after the corpus luteum regresses?
Which stage shows the corpus albicans formed after the corpus luteum regresses?
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What happens to the structure of the active corpus luteum during the oestrous cycle?
What happens to the structure of the active corpus luteum during the oestrous cycle?
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What is a distinctive feature of the corpus albicans?
What is a distinctive feature of the corpus albicans?
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What color is observed in a regressing corpus luteum 2 days after ovulation?
What color is observed in a regressing corpus luteum 2 days after ovulation?
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How is the consistency of the active corpus luteum characterized after its formation?
How is the consistency of the active corpus luteum characterized after its formation?
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What is the development of the corpus luteum during the oestrous cycle of the cow primarily associated with?
What is the development of the corpus luteum during the oestrous cycle of the cow primarily associated with?
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Which of the following describes the corpus luteum at its maximum development?
Which of the following describes the corpus luteum at its maximum development?
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How does the projection type of the corpus luteum vary?
How does the projection type of the corpus luteum vary?
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What happens to the corpus luteum prior to the onset of pro-oestrus?
What happens to the corpus luteum prior to the onset of pro-oestrus?
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What is the effect of palpating the ovary during heat?
What is the effect of palpating the ovary during heat?
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The type of protrusion that develops from the corpus luteum depends on what?
The type of protrusion that develops from the corpus luteum depends on what?
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What does B-mode ultrasound reveal about the corpus luteum?
What does B-mode ultrasound reveal about the corpus luteum?
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What should occur for the corpus luteum to be palpated effectively?
What should occur for the corpus luteum to be palpated effectively?
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What is a common reproductive pattern observed in domesticated animals compared to their wild counterparts?
What is a common reproductive pattern observed in domesticated animals compared to their wild counterparts?
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What initiates the onset of cyclical reproductive activity in animals during favorable conditions?
What initiates the onset of cyclical reproductive activity in animals during favorable conditions?
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What physiological change occurs in female domestic animals as they reach puberty?
What physiological change occurs in female domestic animals as they reach puberty?
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What is the term for the period when female animals are sexually receptive and able to mate?
What is the term for the period when female animals are sexually receptive and able to mate?
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What does the presence of adequate nutrition in spring correlate with in animal reproduction?
What does the presence of adequate nutrition in spring correlate with in animal reproduction?
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What physiological event is most directly associated with the maturation of Graafian follicles in females?
What physiological event is most directly associated with the maturation of Graafian follicles in females?
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Which structure is significantly increased in weight during the prepubertal growth phase in females?
Which structure is significantly increased in weight during the prepubertal growth phase in females?
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In what context do non-seasonal polycyclic animals primarily experience interruptions in their reproductive cycles?
In what context do non-seasonal polycyclic animals primarily experience interruptions in their reproductive cycles?
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What is the state of the cervix during oestrus?
What is the state of the cervix during oestrus?
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What behavioral change is commonly observed in a mare during oestrus?
What behavioral change is commonly observed in a mare during oestrus?
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What happens to the uterus during dioestrus?
What happens to the uterus during dioestrus?
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How does the mare's vulva appear during oestrus?
How does the mare's vulva appear during oestrus?
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What is an observable sign that a mare is not in oestrus when introduced to a stallion?
What is an observable sign that a mare is not in oestrus when introduced to a stallion?
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What is the duration of elevated LH levels surrounding ovulation in mares?
What is the duration of elevated LH levels surrounding ovulation in mares?
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During which phase is the uterus flaccid and not showing increased tone?
During which phase is the uterus flaccid and not showing increased tone?
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What purpose does the temporary pneumovagina serve during examination?
What purpose does the temporary pneumovagina serve during examination?
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What primarily inhibits prolactin secretion in the hypothalamus?
What primarily inhibits prolactin secretion in the hypothalamus?
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What characterizes the formation of the corpus luteum after ovulation?
What characterizes the formation of the corpus luteum after ovulation?
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What effect does naloxone infusion have on gonadotrophin concentrations?
What effect does naloxone infusion have on gonadotrophin concentrations?
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What role do endogenous peptides such as β-endorphin and met-enkephalin play?
What role do endogenous peptides such as β-endorphin and met-enkephalin play?
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What is the change in mass of the corpus luteum in the ewe post-ovulation over 12 days?
What is the change in mass of the corpus luteum in the ewe post-ovulation over 12 days?
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What is the main purpose of the surge system in the reproductive endocrine system?
What is the main purpose of the surge system in the reproductive endocrine system?
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What effect does the steroid environment have on opioid influences?
What effect does the steroid environment have on opioid influences?
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Which cell types are most abundant in the fully formed corpus luteum?
Which cell types are most abundant in the fully formed corpus luteum?
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Which factor initiates the neuro-endocrine reflex leading to ovulation in certain species?
Which factor initiates the neuro-endocrine reflex leading to ovulation in certain species?
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What is the role of inhibin in the reproductive endocrine system?
What is the role of inhibin in the reproductive endocrine system?
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What happens to FSH and LH secretion with the administration of exogenous opioid peptides?
What happens to FSH and LH secretion with the administration of exogenous opioid peptides?
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Which component is NOT typically associated with the tonic/episodic system of the endocrine control?
Which component is NOT typically associated with the tonic/episodic system of the endocrine control?
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What happens to gonadotrophin secretion when the GnRH neurons are activated?
What happens to gonadotrophin secretion when the GnRH neurons are activated?
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Which of the following species are classified as spontaneous ovulators?
Which of the following species are classified as spontaneous ovulators?
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Which hormone is released by the anterior pituitary to stimulate ovarian follicular maturation?
Which hormone is released by the anterior pituitary to stimulate ovarian follicular maturation?
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What effect does oestrogen and inhibin have on the secretion of FSH?
What effect does oestrogen and inhibin have on the secretion of FSH?
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What role does noradrenaline play in ovarian function?
What role does noradrenaline play in ovarian function?
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Which monoamine is associated with inhibiting the basal secretion of LH?
Which monoamine is associated with inhibiting the basal secretion of LH?
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How does the inhibition of dopamine conversion to noradrenaline affect ovulation?
How does the inhibition of dopamine conversion to noradrenaline affect ovulation?
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What is the effect of dopamine on prolactin release?
What is the effect of dopamine on prolactin release?
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Which systems control the secretion of FSH and LH in domestic species?
Which systems control the secretion of FSH and LH in domestic species?
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What is the primary role of serotonin concerning other neurosecretory systems?
What is the primary role of serotonin concerning other neurosecretory systems?
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Which hormone is released from the anterior pituitary that is influenced by noradrenaline?
Which hormone is released from the anterior pituitary that is influenced by noradrenaline?
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Which substance is known to be responsible for ovulation through its influence on LH release?
Which substance is known to be responsible for ovulation through its influence on LH release?
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Study Notes
Endocrine Control of Reproductive Activity
- Episodic/Tonic System: Continuous basal secretion of gonadotrophins (FSH/LH) regulates ovarian functions, including folliculogenesis and ovulation.
- Surge System: Controls rapid and significant LH secretion, crucial for ovulation.
- GnRH Neurons: Activated by hypothalamic centers, leading to a surge of LH.
- Spontaneous Ovulators: Most domestic species ovulate spontaneously, with exceptions being the cat, rabbit, and camel where coitus induces ovulation through sensory receptor stimulation.
Follicular Development and Hormonal Interaction
- Inhibin and Oestradiol: Suppress FSH secretion, with their roles more prominent during the follicular waves of the estrous cycle.
- Prolactin Regulation: Secretion appears spontaneous, primarily inhibited by prolactin inhibitory factor (PIF, believed to be dopamine).
- Follicular Growth: Dominated by FSH with only one follicle reaching ovulation, influenced possibly by unknown intra-ovarian mechanisms.
Role of the Corpus Luteum (CL)
- Formation: CL develops from the Graafian follicle post-ovulation, derived primarily from granulosa and thecal cells.
- Growth Characteristics: CL mass increases rapidly (20-fold over 12 days), with diverse cell types including luteal cells and fibroblasts.
- Blood Supply: The CL has the highest blood supply per tissue unit among organs.
Follicular Waves and Ovarian Size Changes
- Regularity of Follicular Waves: Influenced by genetics and environment, large follicles form during dioestrus but do not significantly alter ovarian shape.
- Measurement and Palpation: Ovaries can vary in size from 2.0 to 2.5 cm, with detection of follicles depending on their size and relationship to the CL.
Physical Characteristics of the CL
- Enlargement: The CL reaches maximum size by the seventh to eighth day of dioestrus, transforming from loose to compact luteinised structures.
- Morphology: The CL presents a color change from dull cream to orange-yellow, depending on its developmental stage.
Projection of the Corpus Luteum
- Surface Projection: As the CL enlarges, it may create a distinct bulge on the ovary's surface, with variation in the degree and type of protrusion observed in different animals.
Changes in CL During Cycle
- Post-Ovulation Changes: The CL remains stable in size and appearance until proestrus; it then undergoes significant size reduction and color change as it regresses.
Factors Influencing Follicular Growth
- Other Hormonal Influences: Metabolic hormones like insulin and IGF-1 may also contribute to follicular growth alongside FSH.
- Inhibitory Mechanisms: Exogenous opioid peptides can inhibit FSH and LH secretion while stimulating prolactin, influenced by the steroid environment in the animal.
Endogenous and Exogenous Control of Ovarian Cyclicity
- Animals typically breed annually, with parturition coinciding with favorable spring conditions for offspring growth.
- Domestic species exhibit extended breeding seasons due to enhanced feeding and housing conditions.
- Non-seasonal polycyclic animals, like cows and sows, can breed throughout the year, while seasonal polycyclic animals revert to natural breeding times.
- Animals must attract mates and be in estrus to breed; all domestic species experience recurring estrous cycles linked to ovarian activity.
- Puberty triggers significant growth in reproductive organs; in gilts, the uterine horn increases by 58%, and the uterus and ovaries grow by 72% and 32%, respectively, between 169 and 186 days of age.
- Noradrenaline plays a role in releasing FSH and LH; other neurochemical interactions influence ovulation regulation.
- Two systems control FSH and LH secretion: the episodic/tonic system (basal secretion) and the surge system (massive gonadotrophin release for ovulation).
- Spontaneous ovulators include most domestic species, while cat, rabbit, and camel are induced ovulators requiring sensory stimulation for ovulation.
- The anterior pituitary stimulates various ovarian functions, including folliculogenesis and corpus luteum formation.
- Inhibin and estradiol suppress FSH secretion, with prolactin secretion driven largely by inhibition from hypothalamically-derived factors.
- The corpus luteum is formed rapidly from the Graafian follicle post-ovulation, showing significant changes in mass and cellular turnover.
- Opioid peptides such as β-endorphin may modulate hormonal secretion dynamics, stimulating prolactin while inhibiting FSH and LH.
- During an estrus cycle, changes in cervical and uterine tone can be palpated; the cervix softens and widens during estrus while becoming firm and narrow during anestrus.
- Signs of estrus in mares include restlessness, frequent micturition, and tail raising when exposed to a stallion, with unique patterns of LH secretion observed during this phase.
- Thorough stud management is crucial for accurately identifying estrus and breeding readiness in mares.
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Description
Test your knowledge on the episodic and tonic systems, along with the functions of key hormones such as FSH, LH, insulin, and GH. This quiz covers the continuous basal secretion of gonadotrophins and their stimulating roles. Dive into the fascinating world of hormonal regulation!
