Reproductive Physiology Practice Questions

Q: All of the following are true regarding the LH surge except:

Ovulation occurs 24 hours after the LH surge.. **Explanation** The LH surge is the critical hormonal trigger for ovulation and the transition from the follicular to the luteal phase. **Why Option C is the correct (False) statement:** Ovulation does not occur exactly 24 hours after the LH surge begins. In clinical physiology, ovulation typically occurs **32 to 36 hours** after the onset of the LH surge and approximately **10 to 12 hours** after the LH peak. A 24-hour timeline is more characteristic of the interval following the **estradiol peak**, not the LH surge itself. **Analysis of other options:** * **Option A:** LH receptors are present on both theca cells (always) and mature granulosa cells (induced by FSH). The surge rapidly triggers luteinization and progesterone production in both cell types. * **Option B:** The LH surge terminates the action of Oocyte Maturation Inhibitor (OMI), allowing the primary oocyte to resume **Meiosis I** (completing it just before ovulation) and progress to Meiosis II, where it arrests in metaphase. * **Option D:** The mean duration of the LH surge is approximately **48 hours**. It typically features a rising limb (14 hours), a plateau (14 hours), and a falling limb (20 hours). **High-Yield NEET-PG Pearls:** * **Trigger:** The LH surge is triggered by a "positive feedback" loop when plasma estradiol levels exceed **200 pg/mL** for at least **36–48 hours**. * **Enzymatic Action:** LH stimulates prostaglandins, plasminogen activator, and collagenase, which weaken the follicular wall (stigma) to allow rupture. * **Urine Testing:** Home ovulation kits detect the LH surge in urine; ovulation usually follows 12–24 hours after a positive urine test (as urine lags behind blood levels).

Q: A 17-year-old primigravida asks what to expect during her pregnancy. What normally occurs during pregnancy?

Blood volume increases. During pregnancy, the maternal body undergoes significant physiological adaptations to meet the metabolic demands of the fetus and protect the mother against blood loss during delivery. **Correct Option: A. Blood volume increases** Total blood volume increases significantly (by 40–50%) starting in the first trimester. This is driven by an increase in both plasma volume and red cell mass. The increase in plasma volume is mediated by the activation of the Renin-Angiotensin-Aldosterone System (RAAS), leading to sodium and water retention. **Explanation of Incorrect Options:** * **B. Hematocrit increases:** While red cell mass increases, the increase in **plasma volume is disproportionately greater**. This results in hemodilution, leading to a physiological decrease in hematocrit and hemoglobin concentration (Physiological Anemia of Pregnancy). * **C. Tidal volume decreases:** Progesterone acts as a direct respiratory stimulant. Consequently, **Tidal Volume (TV) increases** by approximately 40%, leading to increased minute ventilation and a state of physiological respiratory alkalosis. * **D. Functional residual capacity increases:** As the uterus enlarges, it pushes the diaphragm upward by about 4 cm. This reduces the resting volume of the lungs, leading to a **decrease in Functional Residual Capacity (FRC)** and Expiratory Reserve Volume (ERV). **High-Yield NEET-PG Pearls:** * **Cardiac Output:** Increases by 30–50%, peaking at 20–24 weeks. Stroke volume increases early, while Heart Rate increases later in pregnancy. * **Coagulation:** Pregnancy is a **hypercoagulable state** (increased Factors VII, VIII, IX, X, and Fibrinogen; decreased Protein S). * **BP:** Systemic Vascular Resistance (SVR) decreases due to progesterone, leading to a **nadir in blood pressure** during the second trimester.

Q: Estrogen secretion is maximum at which phase of the menstrual cycle?

Before ovulation. ### Explanation **Correct Answer: D. Before ovulation** **Medical Concept:** Estrogen levels fluctuate significantly throughout the menstrual cycle, driven by follicular development. During the **follicular phase**, the selection of a dominant follicle leads to a massive increase in estradiol production by the granulosa cells (via the aromatization of androgens). Estrogen levels reach their absolute **peak approximately 24–36 hours before ovulation**. This "pre-ovulatory surge" is critical because it triggers the switch from negative to positive feedback on the pituitary, resulting in the **LH surge**, which ultimately induces ovulation. A second, smaller peak of estrogen occurs during the mid-luteal phase, secreted by the corpus luteum. **Why other options are incorrect:** * **A. Just before menopause:** This period (perimenopause) is characterized by declining ovarian reserve and erratic, generally lower levels of estrogen as cycles become anovulatory. * **B. At puberty:** While estrogen levels rise during puberty (gonadarche), they do not reach the cyclical peaks seen in a mature, ovulating female. * **C. At menstruation:** During the menstrual phase, both estrogen and progesterone levels are at their **lowest point** due to the regression of the corpus luteum from the previous cycle. **High-Yield NEET-PG Pearls:** * **Two Peaks of Estrogen:** Remember that estrogen has a **bimodal** secretion pattern: the 1st (highest) peak is pre-ovulatory; the 2nd (lower) peak is mid-luteal. * **Progesterone Peak:** Unlike estrogen, progesterone has only **one peak**, occurring during the mid-luteal phase (Day 21 of a 28-day cycle). * **Positive Feedback:** Estrogen must maintain a concentration of >200 pg/mL for approximately 48 hours to trigger the LH surge.

Q: Fetal respiratory movements occur earliest at which gestational age?

11 weeks. **Explanation:** **Correct Option: D (11 weeks)** Fetal breathing movements (FBM) are essential for normal lung development and the strengthening of respiratory muscles (diaphragm and intercostals). While primitive chest wall movements can be detected via high-resolution ultrasound as early as **10–11 weeks of gestation**, 11 weeks is the standard clinical milestone cited in major physiology and OBGYN textbooks (e.g., Ganong, Williams). These movements are irregular and episodic initially, occurring primarily during rapid eye movement (REM) sleep. **Analysis of Incorrect Options:** * **Option A (12 weeks):** While very close, 11 weeks is the earliest documented onset. By 12 weeks, the movements are more established but not the "earliest." * **Option B (16 weeks):** By this stage, FBM are more frequent, but they have already been occurring for over a month. * **Option C (20 weeks):** This is the midpoint of pregnancy. At this stage, FBM are well-developed and are used as a component of the fetal biophysical profile later in pregnancy, but it is far past the point of origin. **High-Yield Clinical Pearls for NEET-PG:** * **Function:** FBM are crucial for the circulation of amniotic fluid into the lungs, providing the mechanical stretch required for alveolar growth. * **Regulation:** FBM are inhibited by **hypoxia** and **hypoglycemia** (unlike adults, where hypoxia stimulates breathing). * **Diurnal Variation:** FBM frequency increases after maternal meals and during the night. * **Biophysical Profile (BPP):** In the third trimester, the presence of at least one episode of FBM lasting $\geq$ 30 seconds within a 30-minute window is considered a normal score (2 points).

Q: Pubarche is primarily due to which hormone?

Testosterone. **Explanation:** **Pubarche** refers to the first appearance of pubic hair during puberty. This physiological milestone is primarily driven by **androgens**. 1. **Why Testosterone is Correct:** Pubarche is a manifestation of **Adrenarche** (the activation of the adrenal cortex) and the subsequent maturation of the gonads. In both males and females, the development of pubic and axillary hair is stimulated by androgens. While adrenal androgens like DHEA and Androstenedione initiate the process, **Testosterone** (and its potent metabolite Dihydrotestosterone) is the definitive hormone responsible for the terminal hair growth in the pubic region. In males, it comes from the testes; in females, it is derived from adrenal precursors and peripheral conversion. 2. **Why Other Options are Incorrect:** * **Growth Hormone (GH):** Primarily responsible for the pubertal height spurt and somatic growth, not secondary sexual characteristics. * **Prolactin:** Primarily involved in lactation and reproductive inhibition; pathologically high levels actually inhibit puberty by suppressing GnRH. * **Estrogen:** Responsible for **Thelarche** (breast development) and the maturation of the female genital tract (vaginal mucosa and uterine growth), but it does not cause pubic hair growth. **High-Yield Clinical Pearls for NEET-PG:** * **Sequence in Girls:** Thelarche (usually first) → Pubarche → Peak Height Velocity → Menarche (usually last). * **Sequence in Boys:** Testicular enlargement (>4ml volume) → Pubarche → Growth Spurt. * **Adrenarche vs. Gonadarche:** Adrenarche (adrenal androgen increase) typically precedes Gonadarche (Hpg-axis activation) by about 2 years. * **Precocious Puberty:** If pubarche occurs before age 8 in girls or age 9 in boys, it warrants investigation for premature adrenarche or androgen-secreting tumors.

Q: Which ion is responsible for preventing polyspermy at the time of fertilization in mammals?

Ca++. **Explanation:** The prevention of polyspermy in mammals primarily occurs through the **Cortical Reaction** (the "slow block"). When a sperm cell fuses with the oocyte's plasma membrane, it triggers a rapid increase in the concentration of **intracellular Calcium (Ca++)** within the oocyte. 1. **Why Ca++ is correct:** The rise in cytosolic Ca++ (released from the endoplasmic reticulum) is the pivotal signal for fertilization. This calcium wave triggers **exocytosis of cortical granules** into the perivitelline space. These granules contain enzymes (like ovastacin) that proteolytically modify the zona pellucida (ZP3 receptors) and harden it, making it impenetrable to other sperm. This process is known as the **Zona Reaction**. 2. **Why other options are incorrect:** * **Na+:** In some non-mammalian species (like sea urchins), a Na+ influx causes a "fast block" by depolarizing the membrane. However, this has not been definitively proven to occur or be significant in human/mammalian fertilization. * **K+ and Mg++:** These ions do not play a primary signaling role in the cortical reaction or the structural modification of the zona pellucida. **High-Yield Facts for NEET-PG:** * **Fast Block:** Electrical depolarization (Na+ dependent); occurs in amphibians/sea urchins, not significant in mammals. * **Slow Block:** Cortical/Zona reaction (Ca++ dependent); the definitive mechanism in mammals. * **Oocyte Activation:** The same Ca++ spike is also responsible for the completion of **Meiosis II** in the secondary oocyte, leading to the formation of the second polar body and the definitive ovum. * **Zinc Sparks:** Recent research highlights that "sparks" of Zinc ions are also released alongside Ca++ during fertilization to assist in cell cycle resumption.

Q: During pregnancy, at what point is the maximum urinary human chorionic gonadotropin (hCG) level typically reached?

70 days of gestation. **Explanation:** Human Chorionic Gonadotropin (hCG) is a glycoprotein hormone secreted by the syncytiotrophoblast of the placenta. Its primary physiological role is to maintain the corpus luteum, ensuring the continued secretion of progesterone until the placenta takes over steroidogenesis (the luteal-placental shift). **Why 70 days is correct:** hCG levels become detectable in maternal serum/urine approximately 8–11 days after conception. The levels rise exponentially, doubling every 48–72 hours. The peak concentration of hCG is typically reached between **8 to 11 weeks of gestation** (60 to 80 days). Therefore, **70 days** (10 weeks) represents the median point of this peak physiological window. After this peak, levels decline to a lower, stable plateau for the remainder of the pregnancy. **Analysis of Incorrect Options:** * **30 days:** At this stage (approx. 4 weeks), hCG is rising rapidly but is still in the early phase of secretion. * **50 days:** While levels are high at 7 weeks, they have not yet reached the maximum peak seen at 10 weeks. * **90 days:** By 12–13 weeks, hCG levels have already begun their characteristic decline from the peak. **High-Yield Clinical Pearls for NEET-PG:** * **Structure:** hCG is a heterodimer. The **α-subunit** is identical to LH, FSH, and TSH; the **β-subunit** is unique and confers biological specificity (this is why pregnancy tests target the β-subunit). * **Doubling Time:** In a healthy intrauterine pregnancy, β-hCG levels should increase by at least 66% every 48 hours. * **Clinical Significance of High hCG:** Abnormally high levels are associated with **Molar pregnancy**, Multiple gestations, and Down Syndrome (Trisomy 21). * **Clinical Significance of Low hCG:** Abnormally low or slow-rising levels suggest Ectopic pregnancy or impending Spontaneous Abortion.

Q: Which of the following decreases during pregnancy?

Systemic venous resistance. ### Explanation In pregnancy, the maternal cardiovascular system undergoes significant adaptation to meet the metabolic demands of the fetus. **1. Why Systemic Vascular Resistance (SVR) Decreases:** The hallmark of cardiovascular change in pregnancy is a **marked decrease in Systemic Vascular Resistance (SVR)**. This occurs due to: * **Progesterone:** Acts as a potent smooth muscle relaxant, causing vasodilation. * **Nitric Oxide & Prostaglandins:** Increased production leads to further vasodilation. * **Low-resistance Circuit:** The placenta acts as a high-flow, low-resistance shunt. This drop in SVR leads to a compensatory increase in cardiac output and a physiological drop in blood pressure during the second trimester. **2. Analysis of Incorrect Options:** * **Cardiac Output (CO):** Increases by 30–50%. This is achieved through increases in both stroke volume (early pregnancy) and heart rate (late pregnancy). * **Heart Rate (HR):** Increases by approximately 10–20 beats per minute to maintain the elevated cardiac output. * **Plasma Volume:** Increases significantly (up to 50%). Since the increase in plasma volume exceeds the increase in red cell mass, it leads to **"Physiological Anemia of Pregnancy."** **3. NEET-PG High-Yield Pearls:** * **Blood Pressure:** Diastolic BP decreases more than Systolic BP; the lowest point is reached at 24–28 weeks. * **Stroke Volume:** Increases early in pregnancy (peaking at 20–24 weeks). * **Uterine Blood Flow:** Increases from ~50 mL/min to ~500–750 mL/min at term. * **Coagulation:** Pregnancy is a **hypercoagulable state** (increase in Factors VII, VIII, IX, X, and Fibrinogen; decrease in Protein S).

Q: Males and females show differences in the age of onset of puberty. What explains the difference in the age of onset of puberty amongst males?

Increased Inhibin levels. **Explanation:** The onset of puberty is governed by the reactivation of the **Hypothalamic-Pituitary-Gonadal (HPG) axis**. While both sexes follow a similar pattern of increasing GnRH pulsatility, the specific hormonal dynamics differ. **Why "Increased Inhibin levels" is correct:** In males, the onset of puberty is closely linked to the maturation of **Sertoli cells**. As these cells mature under the influence of FSH, they begin to secrete **Inhibin B**. Studies have shown that in boys, there is a significant rise in serum Inhibin B levels during early puberty, which serves as a marker of Sertoli cell proliferation and tubular growth. This increase in Inhibin B is one of the earliest endocrine changes observed in males, often preceding the significant rise in testosterone. **Analysis of Incorrect Options:** * **A & B (Activin and Follistatin):** While Activin stimulates and Follistatin inhibits FSH secretion, their systemic levels do not serve as the primary physiological trigger or the distinguishing factor for the timing of male puberty in the same way Inhibin B does. * **D (Easily releasable FSH pool):** This is more characteristic of the **female** HPG axis. In females, the pituitary has a more "readily releasable" pool of FSH and LH, leading to an earlier clinical onset of puberty (thelarche) compared to males. **High-Yield NEET-PG Pearls:** * **First sign of puberty in males:** Increase in testicular volume (≥ 4 ml), measured by a Prader Orchidometer. * **First sign of puberty in females:** Thelarche (breast bud development). * **Inhibin B** is the primary form in males (marker of spermatogenesis), while **Inhibin A** is more relevant in the female menstrual cycle (secreted by the dominant follicle/corpus luteum). * **Leptin:** A critical "permissive" factor; a minimum body fat percentage is required to initiate the HPG axis.

Question 1

Erection is associated with all the following except?

Accepted Answer

Pudendal nerves

Answer

Sacral plexus

Answer

Hypogastric plexus

Answer

Nervi erigentes

Question 2

All of the following are true regarding the LH surge except:

Accepted Answer

Ovulation occurs 24 hours after the LH surge.

Answer

The LH surge acts rapidly on both granulosa and theca cells of the preovulatory follicle.

Answer

The LH surge initiates re-entry of the oocyte into meiosis.

Answer

The mean duration of the LH surge is 48 hours.

Question 3

A 17-year-old primigravida asks what to expect during her pregnancy. What normally occurs during pregnancy?

Accepted Answer

Blood volume increases

Answer

Hematocrit increases

Answer

Tidal volume decreases

Answer

Functional residual capacity increases

Question 4

Estrogen secretion is maximum at which phase of the menstrual cycle?

Accepted Answer

Before ovulation

Answer

Just before menopause

Answer

At puberty

Answer

At menstruation

Question 5

Fetal respiratory movements occur earliest at which gestational age?

Accepted Answer

11 weeks

Answer

12 weeks

Answer

16 weeks

Answer

20 weeks

Question 6

Pubarche is primarily due to which hormone?

Accepted Answer

Testosterone

Answer

Growth Hormone (GH)

Answer

Prolactin

Answer

Estrogen

Question 7

Which ion is responsible for preventing polyspermy at the time of fertilization in mammals?

Accepted Answer

Ca++

Answer

Na+

Answer

K+

Answer

Mg++

Question 8

During pregnancy, at what point is the maximum urinary human chorionic gonadotropin (hCG) level typically reached?

Accepted Answer

70 days of gestation

Answer

30 days of gestation

Answer

50 days of gestation

Answer

90 days of gestation

Question 9

Which of the following decreases during pregnancy?

Accepted Answer

Systemic venous resistance

Answer

Cardiac output (CO)

Answer

Heart rate (HR)

Answer

Plasma volume

Question 10

Males and females show differences in the age of onset of puberty. What explains the difference in the age of onset of puberty amongst males?

Accepted Answer

Increased Inhibin levels

Answer

Increased Activin-A levels

Answer

Decreased Follistatin levels

Answer

Easily releasable FSH pool

Reproductive Physiology — MCQs

Reproductive Physiology — MCQs

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