Endocrinology and Reproductive Biology Quiz

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Questions and Answers

What hormone is primarily responsible for stimulating the production of FSH and LH in the anterior pituitary?

GnRH (correct)

Testosterone

Estrogen

Progesterone

What is the effect of negative feedback in the hormonal regulation of the HPG axis?

Increases GnRH, FSH, and LH levels

Decreases testosterone and estrogen levels

Reduces GnRH, FSH, and LH levels (correct)

Regulates menstrual cycles in females

During what phase do high estrogen levels cause an LH surge in females?

Ovulation (correct)

Follicular phase

Luteal phase

Menstrual phase

How is chromosomal sex determined in mammals?

By the SRY gene and hormonal signaling Signup and view all the answers

Which condition is characterized by XY individuals developing female characteristics due to a lack of androgen receptor response?

Androgen Insensitivity Syndrome Signup and view all the answers

What is the term for the process where spermatogonia undergo mitotic division and eventually develop into mature sperm?

Spermatogenesis Signup and view all the answers

Where does oogenesis primarily occur in females?

Ovarian follicles Signup and view all the answers

What regulates spermatogenesis in males?

FSH and testosterone Signup and view all the answers

What forms during ovulation from primary oocytes?

A secondary oocyte and a polar body Signup and view all the answers

What is the role of the SRY gene in male development?

It induces differentiation of Sertoli and Leydig cells Signup and view all the answers

Which hormone is responsible for the regression of Müllerian ducts in males?

Anti-Müllerian hormone (AMH) Signup and view all the answers

In the absence of the SRY gene, which structure develops from the gonadal ridge?

Ovaries Signup and view all the answers

What initiates the onset of puberty according to the hypothalamic maturation hypothesis?

Increase in GnRH secretion Signup and view all the answers

During sexual differentiation, what drives male genital development?

Testosterone and DHT Signup and view all the answers

What is responsible for the development of internal male reproductive structures?

Testosterone secretion Signup and view all the answers

Which hypothesis suggests that puberty results from decreased sensitivity to gonadal steroid inhibition?

Gonadostat Hypothesis Signup and view all the answers

Which reproductive mode is commonly exhibited by chondrichthyan fishes?

Oviparity Signup and view all the answers

What is the role of prolactin in chondrichthyans?

Influences osmoregulation in water Signup and view all the answers

What is the primary function of the circadian clock in organisms?

Controls both sleep-wake cycles and body temperature Signup and view all the answers

Which hormone is crucial for triggering ovulation in amphibians?

LH Signup and view all the answers

Which of the following accurately describes the interactions of core clock genes?

CLOCK and BMAL1 form a transcriptional activator complex Signup and view all the answers

What type of fertilization is most common among amphibians?

External fertilization Signup and view all the answers

Which of the following is a characteristic of reptile reproductive strategies?

Internal fertilization Signup and view all the answers

How do monarch butterflies utilize their circadian clock during migration?

They use both an internal clock and sun compass Signup and view all the answers

What effect has climate change had on bird migration timing?

Migration timing has shifted earlier in the season Signup and view all the answers

How does temperature affect sex determination in some reptiles?

Higher temperatures often produce males Signup and view all the answers

What type of feedback loop do core clock genes utilize?

Transcription-translation feedback loops Signup and view all the answers

What is the main purpose of estrogen in birds' ovarian function?

Stimulates yolk deposition Signup and view all the answers

What role does light play in the circadian rhythms of monarch butterflies?

It resets their circadian clock daily Signup and view all the answers

Which hormone regulates FSH and LH in bony fishes?

GnRH Signup and view all the answers

Which hormones play a role in synchronizing peripheral clocks?

Cortisol and melatonin Signup and view all the answers

What physiological effect can disruptions in environmental cues have on birds?

Mistimed breeding Signup and view all the answers

What role does leptin play in energy balance?

It works alongside insulin to balance energy intake. Signup and view all the answers

Which hormone is responsible for stimulating parietal cells to secrete HCl in the stomach?

Gastrin Signup and view all the answers

Which of the following is a key function of insulin?

Facilitate cellular glucose uptake. Signup and view all the answers

What is the function of somatostatin in the digestive system?

Inhibits acid secretion and gastrin release. Signup and view all the answers

What triggers the release of glucagon?

Low blood glucose levels. Signup and view all the answers

Which component is released by ECL cells to stimulate acid production?

Histamine Signup and view all the answers

What is the primary role of amylase produced by the pancreas?

Digestion of carbohydrates. Signup and view all the answers

What is the main action of glucagon?

Breakdown of fats for energy. Signup and view all the answers

What is the role of leptin in puberty?

Signals adequate energy reserves for reproduction. Signup and view all the answers

Which cells are responsible for converting androgens into estrogens?

Granulosa cells Signup and view all the answers

What triggers luteolysis in the absence of pregnancy?

Prostaglandin F2α (PGF2α) Signup and view all the answers

What is the main function of the LH surge during the ovarian cycle?

Triggers ovulation by promoting follicle rupture. Signup and view all the answers

What role does cAMP play in LH signaling?

Activates protein kinase A (PKA). Signup and view all the answers

During which phase of the uterine cycle does shedding of the uterine lining occur?

Menstrual Phase Signup and view all the answers

What is the role of FSH in male reproductive physiology?

Supports spermatogenesis and androgen-binding protein secretion. Signup and view all the answers

What prevents luteolysis if pregnancy occurs?

Human chorionic gonadotropin (hCG). Signup and view all the answers

Study Notes

Mammalian Reproduction

The Hypothalamic-Pituitary-Gonadal (HPG) Axis controls pituitary function
Hypothalamus releases GnRH, which controls pituitary function
Anterior Pituitary secretes FSH and LH in response to GnRH
Gonads (testes in males, ovaries in females) produce hormones
- Males: Testes produce testosterone (androgens)
- Females: Ovaries produce estrogen and progesterone
Hormonal Feedback regulates GnRH, FSH, and LH levels in a negative feedback loop
- Testosterone (males) or estrogen/progesterone (females) cause negative feedback
- High estrogen in females during ovulation causes positive feedback, leading to an LH surge and ovulation
Differences in males and females:
- Males: Continuous sperm and testosterone production
- Females: Cyclic ovarian activity (estrous or menstrual cycles)

Sex vs. Gender

Biological Sex is defined by physical traits:
- Chromosomal sex (XX or XY)
- Gonadal sex (testes or ovaries)
- Phenotypic sex (external genitalia, secondary sex characteristics)
Gender is psychological and social identity, not necessarily aligned with biological sex
Sex is influenced by societal norms and individual experience
Intersex Variations occur when chromosomal, gonadal, or phenotypic sex do not align.
- Examples: Androgen Insensitivity Syndrome (AIS) and Congenital Adrenal Hyperplasia (CAH)

Gametogenesis: Spermatogenesis and Oogenesis

Spermatogenesis: occurs in seminiferous tubules of testes
- Process: Spermatogonia (diploid stem cells) divide mitotically, into spermatocytes and then meiosis, producing spermatids that mature to spermatozoa
Oogenesis: occurs in ovarian follicles
- Process: Oogonia divide mitotically during fetal development, primary oocytes are arrested in prophase I until puberty, meiosis I completes during ovulation to form a secondary oocyte and a polar body, Secondary oocyte completes meiosis II upon fertilization

Ovarian and Testes Development

Testes Development:
- SRY gene located on Y chromosome encodes TDF (Testis-Determining Factor)
- TDF induces differentiation of Sertoli cells and Leydig cells, leading to the development of testes
Hormonal Signals: Sertoli cells secrete AMH (anti-Müllerian hormone), causing regression of Müllerian ducts, and Leydig cells produce testosterone promoting Wolffian duct development into internal male reproductive structures
Ovary development occurs in absence of SRY gene:
- Müllerian ducts persist and develop into the uterus, fallopian tubes, and upper vagina
- Lack of testosterone causes regression of Wolffian ducts.

Stages of Differentiation

Chromosomal Sex is determined at fertilization (XX or XY)
Gonadal Sex is determined by presence of SRY gene (testes) or absence (ovaries)
Phenotypic Sex is determined by hormones
- Testosterone and DHT drive male genital development.
- Absence of testosterone results in female genital development.

Puberty

Hypotheses:
- Hypothalamic Maturation Hypothesis: Puberty begins when the hypothalamus increases GnRH secretion, triggered by changes in sensitivity to steroid negative feedback.
- Gonadostat Hypothesis: Puberty occurs when hypothalamic and pituitary sensitivity to gonadal steroid inhibition decreases, leading to increased LH and FSH secretion.
Energy Availability: Puberty may be influenced by metabolic signals like leptin, signaling adequate energy reserves for reproduction.

Two-Cell Model (Ovarian Steroidogenesis)

Theca Cells: Stimulated by LH to produce androgens (e.g. androstenedione)
Granulosa Cells: Stimulated by FSH to convert androgens into estrogens (e.g. estradiol) via aromatase
Male Equivalent: Leydig cells produce testosterone, Sertoli cells support spermatogenesis and androgen-binding protein secretion

Sexual Differentiation

DHT (dihydrotestosterone): promotes external male genitalia development
AMH (Anti-Müllerian Hormone): causes Müllerian duct regression in males.

Luteolysis

Definition: Breakdown of the corpus luteum when pregnancy does not occur
Mechanism: Triggered by prostaglandin F2α (PGF2α), reducing luteal blood flow and suppressing progesterone production
Purpose: Ensuring the next estrous or menstrual cycle

Uterine Cycle

Menstrual Phase: Shedding of the uterine lining if no implantation occurs, triggered by falling progesterone and estrogen
Proliferative Phase: Estrogen from developing follicles stimulates the regrowth of the endometrium
Secretory Phase: Progesterone from the corpus luteum prepares the endometrium for implantation. If no implantation occurs, luteolysis leads to endometrial shedding.

Hormonal Regulation (Parturition/Childbirth)

FSH and LH stimulate follicular development and ovulation
Estrogen promotes endometrial regrowth
Progesterone maintains the endometrium during the secretory phase

Lactation

Preparation During Pregnancy: Estrogen promotes ductal growth, progesterone stimulates lobular-alveolar development, Prolactin prepares mammary glands for milk synthesis
Milk Production: Post-parturition, progesterone, and estrogen levels drop, removing inhibitory effects to allow prolactin to stimulate milk production in alveolar cells. Oxytocin promotes milk ejection.
Lactational Amenorrhea: Suckling suppresses GnRH release, reducing FSH and LH secretion, delaying ovulation.

Menopause

Definition: Permanent cessation of menstrual cycles due to ovarian follicle depletion
Hormonal Changes: Decline in estrogen and progesterone as ovarian activity ceases; increase in FSH, LH due to lack of negative feedback.

Reproductive Cycles (Non-mammals)

Estrous Cycle (non-primates):
- Proestrus: Follicle development, rising estrogen
- Estrus: Ovulation, peak sexual receptivity
- Metestrus: Corpus luteum formation, progesterone
- Diestrus: High progesterone maintains uterine lining
Menstrual Cycle (primates):
- Uterine lining is shed during menstrual phase
- Includes follicular and luteal phases under hormonal control
Seasonal Breeders: Animals like sheep and deer have cycles controlled by day length (photoperiod)

General Reproductive Features

Variation between Oviparous, Ovoviviparous, and Viviparous species
Reproductive strategies varies between species
Oviparous species lay eggs (e.g., most fish, reptiles, and birds).
Ovoviviparous species retain eggs internally until hatching e.g., sharks and reptiles
Viviparous species give live birth e.g., some bony fishes and reptiles.

Hormonal Regulation (various species):

FSH stimulated spermatogenesis
LH regulates testosterone production in Leydig cells
Estrogen stimulates vitellogenin (yolk) synthesis in the liver
Progesterone involved in final oocyte maturation and ovulation
GnRH regulates FSH and LH
Prolactin regulates parental behaviours

Hormonal Impacts

Various species regulate reproductive cycles through temperature, photoperiod (day length)

Climate Change and Migration (Birds)

Timing of migration is shifting due to climate change
Changes in environmental conditions have advanced male gonadal activation by several days annually

Opioids and Cannabinoids

Endogenous Cannabinoid System (ECS) is similar to THC and CBD
- Modulates the hypothalamic-pituitary-adrenal (HPA) axis
- Inhibits glutamate release (reducing excitatory input)
Cannabinoid signaling and seasonality are influenced by melatonin to increase adaptation to seasonal changes.
Opioid system modulates pain, stress, and endocrine functions.

Diabetes

Diabetes results from dysregulated blood glucose levels due to Type 1 Diabetes (Insufficient insulin production by β-cells) and Type 2 Diabetes (Insulin resistance in target tissues)
Elevated blood glucose leads to glucosuria (glucose in urine) when renal glucose reabsorption capacity is exceeded
Chronic glucosuria can cause kidney damage and failure

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Description

Test your knowledge on the key hormones and processes involved in the regulation of the human reproductive system. This quiz covers topics like the HPG axis, oogenesis, spermatogenesis, and factors influencing sexual differentiation. Perfect for students of endocrinology or reproductive biology.