Hormonal Regulation Quiz

Questions and Answers

What is the primary function of the episodic/tonic system?

To induce ovulation through sensory stimulation.

To control short-lived massive secretion of gonadotrophins.

To regulate the menstrual cycle in all domestic species.

To stimulate the continuous basal secretion of gonadotrophins. (correct)

Which hormone is primarily responsible for inducing ovulation in certain species?

FSH

Insulin

LH (correct)

In which animals is ovulation not spontaneous and induced during copulation?

Horse, rabbit, and camel

Goat, sheep, and rabbit

Rabbit, cat, and camel (correct)

Dog, cat, and cow

Which factor is involved in suppressing FSH secretion?

Oestrogens and inhibin Signup and view all the answers

Which component directly stimulates ovarian functions such as folliculogenesis?

LH Signup and view all the answers

What initiates the neuro-endocrine reflex leading to the activation of GnRH neurons?

Stimulation of sensory receptors at coitus Signup and view all the answers

What is the result of the activation of GnRH neurons in the surge center?

Surge of LH release Signup and view all the answers

What role does the anterior pituitary play related to the ovaries?

It has a direct effect on folliculogenesis and corpus luteum formation. Signup and view all the answers

What role does dopamine play in the secretion of prolactin?

It acts as both a stimulant and an inhibitor of prolactin secretion. Signup and view all the answers

Which cells primarily form the corpus luteum after ovulation?

Granulosa and thecal cells. Signup and view all the answers

What substance is believed to inhibit prolactin secretion?

Prolactin inhibitory factor. Signup and view all the answers

How does the administration of exogenous opioid peptides affect FSH and LH secretion?

It inhibits FSH and LH secretion while stimulating prolactin secretion. Signup and view all the answers

What change occurs in the corpus luteum's mass after ovulation in the ewe?

It increases by 20-fold over 12 days. Signup and view all the answers

What happens to gonadotrophin concentrations when naloxone is infused?

They increase in mean concentrations. Signup and view all the answers

Which cell types comprise the largest percentage of the corpus luteum in the ewe?

Large luteal cells. Signup and view all the answers

What type of activity have endogenous peptides like β-endorphin and met-enkephalin been found to exhibit?

Opioid activity. Signup and view all the answers

What is the role of FSH in the normal oestrous cycle?

It stimulates follicular growth. Signup and view all the answers

What is observed about the corpus luteum after 48 hours post-ovulation?

It has a diameter of about 1.4 cm. Signup and view all the answers

What is likely responsible for the dominance of one follicle over others?

Unknown intra-ovarian mechanisms. Signup and view all the answers

What is the typical size range for large follicles during dioestrus?

0.7–1.5 cm in diameter. Signup and view all the answers

What is a characteristic of the corpus luteum by the seventh to eighth day of dioestrus?

It is yellow to orange-yellow in color. Signup and view all the answers

What effect does the presence of large follicles during dioestrus have on the ovaries?

They cause overall variation in gross ovarian size. Signup and view all the answers

How does the corpus luteum feel upon palpation 48 hours after ovulation?

It is soft and yields on palpation. Signup and view all the answers

What kind of cells contribute to the development of the corpus luteum?

Granulosa cells. Signup and view all the answers

What color is the active corpus luteum just after ovulation in a nulliparous heifer?

Orange-yellow Signup and view all the answers

What indicates the regression of a corpus luteum?

Dense and blood-stained appearance Signup and view all the answers

How does the size of an ovary change during oestrus?

Depends on the presence of an active corpus luteum Signup and view all the answers

Which stage shows the corpus albicans formed after the corpus luteum regresses?

Stage C Signup and view all the answers

What happens to the structure of the active corpus luteum during the oestrous cycle?

It decreases in size and develops a dense consistency Signup and view all the answers

What is a distinctive feature of the corpus albicans?

It appears as scar tissue Signup and view all the answers

What color is observed in a regressing corpus luteum 2 days after ovulation?

Bright yellow Signup and view all the answers

How is the consistency of the active corpus luteum characterized after its formation?

Loose with a central cavity Signup and view all the answers

What is the development of the corpus luteum during the oestrous cycle of the cow primarily associated with?

Formation of a distinct projection from the ovary Signup and view all the answers

Which of the following describes the corpus luteum at its maximum development?

It forms a distinct bulge about 1 cm in diameter Signup and view all the answers

How does the projection type of the corpus luteum vary?

It can be nipple-like or diffuse Signup and view all the answers

What happens to the corpus luteum prior to the onset of pro-oestrus?

It maintains its maximum size and appearance Signup and view all the answers

What is the effect of palpating the ovary during heat?

It may detect the collapse of an ovary Signup and view all the answers

The type of protrusion that develops from the corpus luteum depends on what?

The extent of the surface of the ovary occupied by the follicle before ovulation Signup and view all the answers

What does B-mode ultrasound reveal about the corpus luteum?

It may show a speckled area corresponding to the corpus luteum and follicle Signup and view all the answers

What should occur for the corpus luteum to be palpated effectively?

Examination during heat and the following 24 hours is required Signup and view all the answers

What is a common reproductive pattern observed in domesticated animals compared to their wild counterparts?

They breed year-round due to environmental control. Signup and view all the answers

What initiates the onset of cyclical reproductive activity in animals during favorable conditions?

Environmental light and warmth. Signup and view all the answers

What physiological change occurs in female domestic animals as they reach puberty?

Increase in the size of the genital organs. Signup and view all the answers

What is the term for the period when female animals are sexually receptive and able to mate?

Oestrous cycle. Signup and view all the answers

What does the presence of adequate nutrition in spring correlate with in animal reproduction?

Increase in successful mating. Signup and view all the answers

What physiological event is most directly associated with the maturation of Graafian follicles in females?

Shedding of ova. Signup and view all the answers

Which structure is significantly increased in weight during the prepubertal growth phase in females?

Ovaries. Signup and view all the answers

In what context do non-seasonal polycyclic animals primarily experience interruptions in their reproductive cycles?

During pregnancy and lactation. Signup and view all the answers

What is the state of the cervix during oestrus?

Soft and broad Signup and view all the answers

What behavioral change is commonly observed in a mare during oestrus?

Frequent lifting of the tail Signup and view all the answers

What happens to the uterus during dioestrus?

It increases in tone and thickness Signup and view all the answers

How does the mare's vulva appear during oestrus?

Slightly oedematous Signup and view all the answers

What is an observable sign that a mare is not in oestrus when introduced to a stallion?

Aggressive behavior Signup and view all the answers

What is the duration of elevated LH levels surrounding ovulation in mares?

5-6 days Signup and view all the answers

During which phase is the uterus flaccid and not showing increased tone?

Anoestrus Signup and view all the answers

What purpose does the temporary pneumovagina serve during examination?

To assist in internal examinations Signup and view all the answers

What primarily inhibits prolactin secretion in the hypothalamus?

Dopamine Signup and view all the answers

What characterizes the formation of the corpus luteum after ovulation?

It forms primarily from granulosa and thecal cells. Signup and view all the answers

What effect does naloxone infusion have on gonadotrophin concentrations?

Increases gonadotrophin levels. Signup and view all the answers

What role do endogenous peptides such as β-endorphin and met-enkephalin play?

Inhibiting prolactin secretion. Signup and view all the answers

What is the change in mass of the corpus luteum in the ewe post-ovulation over 12 days?

Increases 20-fold. Signup and view all the answers

What is the main purpose of the surge system in the reproductive endocrine system?

To stimulate ovulation through LH release Signup and view all the answers

What effect does the steroid environment have on opioid influences?

It enhances the suppression of gonadotrophin secretion. Signup and view all the answers

Which cell types are most abundant in the fully formed corpus luteum?

Large luteal cells comprise 25-35%. Signup and view all the answers

Which factor initiates the neuro-endocrine reflex leading to ovulation in certain species?

Sensory receptor activation in the vagina and cervix Signup and view all the answers

What is the role of inhibin in the reproductive endocrine system?

To suppress FSH secretion Signup and view all the answers

What happens to FSH and LH secretion with the administration of exogenous opioid peptides?

It inhibits the secretion of both. Signup and view all the answers

Which component is NOT typically associated with the tonic/episodic system of the endocrine control?

Oxytocin Signup and view all the answers

What happens to gonadotrophin secretion when the GnRH neurons are activated?

Surge in LH secretion only Signup and view all the answers

Which of the following species are classified as spontaneous ovulators?

All domestic species except cat, rabbit, and camel Signup and view all the answers

Which hormone is released by the anterior pituitary to stimulate ovarian follicular maturation?

FSH Signup and view all the answers

What effect does oestrogen and inhibin have on the secretion of FSH?

They suppress FSH secretion Signup and view all the answers

What role does noradrenaline play in ovarian function?

Stimulates the release of FSH and LH Signup and view all the answers

Which monoamine is associated with inhibiting the basal secretion of LH?

Serotonin Signup and view all the answers

How does the inhibition of dopamine conversion to noradrenaline affect ovulation?

It blocks the release of LH necessary for ovulation Signup and view all the answers

What is the effect of dopamine on prolactin release?

It inhibits prolactin release Signup and view all the answers

Which systems control the secretion of FSH and LH in domestic species?

Two functionally separate but superimposable systems Signup and view all the answers

What is the primary role of serotonin concerning other neurosecretory systems?

Regulating their activities Signup and view all the answers

Which hormone is released from the anterior pituitary that is influenced by noradrenaline?

FSH Signup and view all the answers

Which substance is known to be responsible for ovulation through its influence on LH release?

Estradiol Signup and view all the answers

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!