Reproductive Physiology Practice Questions

Q: What is the efferent pathway for the milk ejection reflex?

Oxytocin. The **Milk Ejection Reflex** (also known as the "Let-down reflex") is a neuroendocrine reflex initiated by suckling. ### **Explanation of the Correct Answer (B)** When an infant suckles, tactile receptors on the nipple send afferent impulses via the somatic nerves to the **supraoptic and paraventricular nuclei** of the hypothalamus. This triggers the release of **Oxytocin** from the posterior pituitary into the bloodstream. Oxytocin acts as the **efferent hormonal pathway**, traveling to the mammary glands where it causes the contraction of **myoepithelial cells** surrounding the alveoli. This contraction forces milk from the alveoli into the ducts and out through the nipple. ### **Why Other Options are Incorrect** * **A. Prolactin:** While essential for lactation, Prolactin is responsible for the **production and secretion** of milk (milk synthesis) within the alveolar cells, not its ejection. * **C. ACTH:** Adrenocorticotropic hormone stimulates the adrenal cortex to release cortisol. It has no direct role in the acute milk ejection reflex. * **D. Growth Hormone:** GH is involved in the development of mammary tissue (mammogenesis) and general metabolism but does not trigger milk let-down. ### **NEET-PG High-Yield Pearls** * **Afferent Pathway:** Neural (Somatic nerves to Hypothalamus). * **Efferent Pathway:** Humoral/Hormonal (Oxytocin via blood). * **Psychogenic Inhibition:** Stress, fear, or pain can inhibit oxytocin release (via increased sympathetic tone), thereby blocking the milk ejection reflex. * **Conditioned Reflex:** The reflex can be "conditioned"; the mere sight or cry of the baby can trigger oxytocin release and milk let-down. * **Uterine Effect:** Oxytocin released during breastfeeding also causes uterine contractions (involution), helping the uterus return to its pre-pregnancy size.

Q: During which phase of the human sexual response cycle is it physiologically impossible for males to achieve erection or orgasm?

Resolution. **Explanation:** The human sexual response cycle, as described by Masters and Johnson, consists of four phases: Excitement, Plateau, Orgasm, and Resolution. The **Resolution Phase** is the correct answer because it is characterized by the **Refractory Period** in males. This is a physiological interval immediately following orgasm during which it is impossible to achieve another erection or ejaculation, regardless of the level of stimulation. This occurs due to the release of **prolactin**, which inhibits dopamine (the primary driver of sexual arousal), and the dominance of the sympathetic nervous system, which causes vasoconstriction and detumescence. **Analysis of Incorrect Options:** * **Excitement Phase:** This is the initial stage where parasympathetic stimulation leads to vasocongestion and the *initiation* of an erection. * **Plateau Phase:** This is the period of intensified sexual tension preceding orgasm. Erection is maintained and reaches its peak during this stage. * **Orgasm:** This is the climax of the cycle, characterized by rhythmic contractions of the pelvic musculature and ejaculation. It is the event that *triggers* the subsequent refractory period, but is not the period of physiological impossibility itself. **High-Yield Facts for NEET-PG:** * **Refractory Period:** Only occurs in males. Females are physiologically capable of multiple orgasms without a mandatory refractory interval. * **Neurobiology:** Parasympathetic nerves (S2-S4) mediate **E**rection ("**P**oint"), while Sympathetic nerves (T11-L2) mediate **E**jaculation ("**S**hoot"). * **Prolactin's Role:** Elevated prolactin levels post-orgasm are responsible for the "sexual satiety" and the duration of the refractory period. Pathological hyperprolactinemia (e.g., prolactinoma) can lead to erectile dysfunction.

Q: How many ovum/ova are formed from one primary oocyte?

1. **Explanation:** The process of **oogenesis** is characterized by unequal cytoplasmic division, which ensures that the resulting zygote has sufficient nutrient reserves. **Why Option A is Correct:** A single **primary oocyte** (diploid, 2n) undergoes Meiosis I to produce one **secondary oocyte** and the first polar body. The secondary oocyte then undergoes Meiosis II (completed only upon fertilization) to produce **one functional ovum** and a second polar body. The polar bodies are small, non-functional cells that eventually degenerate. Thus, the net yield from one primary oocyte is exactly **one haploid ovum**. **Why Other Options are Incorrect:** * **Options B & C:** These are incorrect because the division is asymmetrical. While four nuclei are technically produced if the first polar body divides, only one becomes a viable gamete. * **Option D:** This is a common distractor based on **spermatogenesis**. In males, one primary spermatocyte undergoes symmetrical division to produce **four functional spermatozoa**. In females, the "waste" of genetic material into polar bodies prevents the formation of four ova. **High-Yield NEET-PG Pearls:** * **Meiotic Arrests:** Oogenesis halts twice. First, in **Prophase I (Diplotene stage)** at birth, and second, in **Metaphase II** during ovulation (completed only if sperm entry occurs). * **Dictyate Stage:** The prolonged resting phase in Prophase I is also known as the Dictyate stage. * **Polar Bodies:** These serve as a mechanism to discard extra chromosomes while retaining almost all the cytoplasm in a single cell.

Q: Given that one secondary oocyte is produced in each menstrual cycle, how many secondary oocytes are produced on average during the reproductive life of a human female?

420. **Explanation:** The number of secondary oocytes produced during a woman’s reproductive life is determined by the duration of her fertility and the frequency of ovulation. **1. Why the Correct Answer (D) is Right:** The calculation is based on the average reproductive span of a human female: * **Reproductive Years:** Menarche (onset) occurs at ~12–13 years, and Menopause (cessation) occurs at ~45–50 years. This gives an average reproductive window of **35 years**. * **Cycles per Year:** With an average menstrual cycle of 28 days, a woman undergoes approximately **12–13 ovulations per year**. * **Calculation:** 35 years × 12 cycles/year = **420 secondary oocytes**. Since only one dominant follicle typically reaches the stage of ovulation (releasing a secondary oocyte) per cycle, the total number is approximately 400–450. **2. Why Incorrect Options are Wrong:** * **Option A (420,000):** This represents the approximate number of **primary oocytes** present in the ovaries at **puberty**. Most undergo atresia before ovulation. * **Option B (42,000) & C (4,200):** These are mathematically incorrect orders of magnitude that do not correlate with the physiological timeline of the human menstrual cycle. **3. High-Yield NEET-PG Pearls:** * **Oogonia Count:** At 5 months of intrauterine life, there are ~7 million oogonia. At birth, this drops to ~2 million. By puberty, only ~400,000 remain. * **Meiotic Arrest:** Primary oocytes are arrested in **Prophase I (Diplotene stage)** until puberty. The secondary oocyte is arrested in **Metaphase II** until fertilization. * **Atresia:** Over 99% of the follicles present at birth undergo a degenerative process called atresia; only ~0.1% ever ovulate.

Q: Which hormone is not affected by the menstrual cycle?

Prolactin. **Explanation:** The menstrual cycle is governed by the rhythmic fluctuation of hormones within the Hypothalamic-Pituitary-Ovarian (HPO) axis. **Why Prolactin is the Correct Answer:** Prolactin is primarily involved in lactogenesis and is regulated by the inhibitory effect of **Dopamine** from the hypothalamus. Unlike other reproductive hormones, Prolactin levels remain relatively **stable** throughout the normal menstrual cycle in non-pregnant, non-lactating women. It does not play a direct role in the cyclical changes of the endometrium or ovulation. **Why the Other Options are Incorrect:** * **Estrogen:** Levels fluctuate significantly, peaking twice: once during the late follicular phase (triggering the LH surge) and again during the mid-luteal phase. * **Progesterone:** This hormone is cycle-dependent, with levels being very low during the follicular phase and rising sharply after ovulation (secreted by the **Corpus Luteum**) during the luteal phase. * **Gonadotropins (FSH and LH):** These pituitary hormones show dramatic variations. FSH rises at the start of the cycle to recruit follicles, and both FSH and LH exhibit a massive **pre-ovulatory surge** triggered by positive feedback from estrogen. **High-Yield Clinical Pearls for NEET-PG:** * **Prolactin & Amenorrhea:** While Prolactin doesn't change *with* the cycle, pathologically high levels (Hyperprolactinemia) inhibit GnRH pulsatility, leading to secondary amenorrhea and infertility. * **The "LH Surge":** Occurs 24–36 hours before ovulation; it is the most reliable predictor of ovulation. * **Progesterone:** The "Thermogenic Hormone"—the rise in progesterone during the luteal phase causes a 0.5°F increase in Basal Body Temperature (BBT).

Q: Which of the following arteries supplying the uterus is insensitive to hormonal changes?

Basal arteries. The uterine blood supply is organized into distinct layers, and understanding the functional anatomy of the endometrium is crucial for NEET-PG. **Explanation of the Correct Answer:** The endometrium is divided into two layers: the **stratum basalis** (deep) and the **stratum functionalis** (superficial). The **Basal arteries** supply the stratum basalis. These arteries are **insensitive to hormonal changes** (estrogen and progesterone). Because they do not constrict or undergo necrosis during the late luteal phase, the basal layer remains intact during menstruation, serving as the regenerative source for the new endometrium in the subsequent cycle. **Analysis of Incorrect Options:** * **Spiral arteries:** These supply the stratum functionalis. They are **highly sensitive** to hormonal fluctuations. When progesterone levels drop at the end of the cycle, these arteries undergo intense vasoconstriction and rhythmic spasms, leading to ischemia and the shedding of the functional layer (menstruation). * **Radial arteries:** These arise from the arcuate arteries and penetrate the myometrium. They are the parent vessels that branch into both basal and spiral arteries. While they are not the primary site of menstrual shedding, the question specifically targets the endometrial vessels where the distinction in hormonal sensitivity is a defining physiological characteristic. **High-Yield Clinical Pearls for NEET-PG:** * **Regeneration:** The stratum basalis (supplied by basal arteries) is the "permanent" layer; the stratum functionalis (supplied by spiral arteries) is the "deciduous" layer. * **Menstrual Mechanism:** The withdrawal of progesterone causes the release of **Prostaglandin F2α**, which triggers the vasospasm of the spiral arteries. * **Vascular Path:** Uterine artery → Arcuate artery → Radial artery → Basal/Spiral artery.

Q: What is the earliest hormonal sign of puberty?

Sleep-associated increase in LH. ### Explanation The onset of puberty is triggered by the reactivation of the **GnRH pulse generator** (the "gonadostat") in the hypothalamus. **1. Why Option A is Correct:** The earliest detectable hormonal change of puberty is the **nocturnal (sleep-associated) increase in the pulsatile secretion of Luteinizing Hormone (LH)**. Initially, these pulses occur only during REM sleep. As puberty progresses, the amplitude and frequency of these LH pulses increase and eventually occur throughout the day and night. This shift marks the transition from the prepubertal state to active puberty. **2. Why Other Options are Incorrect:** * **Option B:** Early morning rise in temperature is associated with ovulation (progesterone effect) in the luteal phase of the menstrual cycle, not the onset of puberty. * **Option C:** In the **prepubertal** period, FSH levels are higher than LH levels. At the **onset of puberty**, this ratio reverses, and **LH becomes dominant** over FSH. Therefore, a *decreased* FSH to LH ratio is seen in puberty. * **Option D:** Elevated adrenal androgens (DHEA, DHEAS) characterize **Adrenarche**, which typically occurs around age 6–8. While it precedes puberty, it is a separate physiological process and not the hormonal trigger for true gonadal puberty (Gonadarche). ### High-Yield Clinical Pearls for NEET-PG: * **First Physical Sign (Females):** Thelarche (breast bud development), driven by Estrogen. * **First Physical Sign (Males):** Increase in testicular volume (>4 ml), driven by Testosterone. * **Order of Puberty (Females):** Thelarche → Pubarche → Growth Spurt → Menarche. * **Leptin's Role:** Adequate body fat and leptin levels are permissive for the onset of puberty by stimulating GnRH release.

Question 1

What is the efferent pathway for the milk ejection reflex?

Accepted Answer

Oxytocin

Answer

Prolactin

Answer

ACTH

Answer

Growth hormone

Question 2

During sexual differentiation in males, what occurs?

Accepted Answer

Primitive gonads differentiate into testes due to the presence of the SRY gene.

Answer

Leydig cells produce Mullerian Inhibiting Substance.

Answer

Androgen binding protein is responsible for the development of male external genitalia.

Answer

The Wolffian duct regresses.

Question 3

During which phase of the human sexual response cycle is it physiologically impossible for males to achieve erection or orgasm?

Accepted Answer

Resolution

Answer

Excitement Phase

Answer

Plateau Phase

Answer

Orgasm

Question 4

Which of the following is NOT related to the corpus luteum?

Accepted Answer

The peak steroid production is between the 23rd and 25th day.

Answer

Luteinised granulosa cells produce progesterone.

Answer

Estrogen continues to be produced by the luteinised granulosa cells.

Answer

Luteolysis is due to estrogen, PGF2a, and endothelin.

Question 5

How many ovum/ova are formed from one primary oocyte?

Accepted Answer

1

Answer

2

Answer

3

Answer

4

Question 6

Given that one secondary oocyte is produced in each menstrual cycle, how many secondary oocytes are produced on average during the reproductive life of a human female?

Accepted Answer

420

Answer

420,000

Answer

42,000

Answer

4,200

Question 7

Which hormone is not affected by the menstrual cycle?

Accepted Answer

Prolactin

Answer

Estrogen

Answer

Progesterone

Answer

Gonadotropins

Question 8

Which of the following arteries supplying the uterus is insensitive to hormonal changes?

Accepted Answer

Basal arteries

Answer

Radial arteries

Answer

Spiral arteries

Answer

None of the above

Question 9

What hormonal changes are characteristic of the luteal phase?

Accepted Answer

Increased progesterone levels

Answer

Decreased progesterone levels

Answer

Decreased estrogen level

Answer

None of the above

Question 10

What is the earliest hormonal sign of puberty?

Accepted Answer

Sleep-associated increase in LH

Answer

Early morning rise in temperature

Answer

Increased FSH to LH ratio

Answer

Elevated adrenal androgens

Reproductive Physiology — MCQs

Reproductive Physiology — MCQs

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