NEET-PG 2013 - Physiology Practice Questions

Q: Which of the following is the primary site of gastrin production?

Gastric G cells. ***Gastric G cells*** - **G cells**, primarily located in the **antrum of the stomach**, are the main site for **gastrin production** - Gastrin is a hormone that stimulates the secretion of **gastric acid** by the parietal cells in the oxyntic glands of the stomach - G cells are specialized endocrine cells that release gastrin in response to gastric distension, amino acids, and vagal stimulation *Pancreas* - The pancreas produces hormones such as **insulin** and **glucagon**, and digestive enzymes like **amylase** and **lipase** - While the pancreas does contain some hormone-producing cells, it is not the primary site for gastrin synthesis *Pituitary gland* - The **pituitary gland** is the master endocrine gland, regulating various **hormonal axes** like thyroid, adrenal, and reproductive functions - It does not produce gastrin; its hormones include **growth hormone**, **prolactin**, **TSH**, **ACTH**, **FSH**, and **LH** *Gastric chief cells* - Chief cells (also called zymogenic cells) are located in the **gastric glands of the fundus and body** of the stomach - They produce **pepsinogen**, the inactive precursor of the proteolytic enzyme pepsin, not gastrin

Q: What is the primary hormone responsible for the secretion of milk?

Prolactin. ***Prolactin*** - **Prolactin** is the primary hormone synthesized and secreted by the pituitary gland that is responsible for **milk production** (lactogenesis) in the mammary glands after childbirth. - Its levels rise significantly during pregnancy and remain elevated with regular suckling, which stimulates its release and maintains milk supply. *Oxytocin* - **Oxytocin** is primarily responsible for the **milk ejection reflex** (let-down reflex), causing the contraction of myoepithelial cells around the alveoli to release milk. - It does not stimulate the production of milk itself but rather its expulsion from the breast. *Glucocorticoids* - **Glucocorticoids** (like cortisol) play a role in mammary gland development and maturation, and can have permissive effects on prolactin's action. - However, they are not the primary hormone directly responsible for stimulating milk secretion. *Relaxin* - **Relaxin** is a hormone primarily involved in relaxing ligaments in the pelvis and softening the cervix during childbirth. - It has no direct primary role in the production or secretion of breast milk.

Q: Which of the following hormones is not stored in cells?

Cortisol. ***Cortisol*** - Cortisol is a **steroid hormone** that is synthesized from **cholesterol** on demand and is **not stored** in secretory vesicles or elsewhere within cells. - Being **lipophilic**, it diffuses freely across cell membranes immediately after synthesis. - Its release is regulated by the **hypothalamic-pituitary-adrenal (HPA) axis**, with synthesis and immediate secretion occurring upon stimulation. *Insulin* - Insulin is a **peptide hormone** synthesized as **proinsulin** and then cleaved into active insulin. - It is **stored in secretory granules** within pancreatic beta cells, allowing for rapid release in response to elevated blood glucose. *Thyroxine* - Thyroxine (T4) is a **thyroid hormone** that is synthesized from tyrosine and iodine. - It is **stored extracellularly** within the thyroid gland's follicles as part of a large protein called **thyroglobulin**. - Unlike cortisol (which is never stored), thyroxine has a **substantial storage pool** that can last weeks, though the storage is extracellular rather than intracellular. *Renin* - Renin is an **enzyme** produced by the **juxtaglomerular cells** of the kidney. - It is **stored in secretory granules** within these cells and released in response to decreased renal perfusion pressure or sympathetic stimulation.

Q: LH surge is associated with?

Increased estrogen & decreased progesterone. ***Increased estrogen & decreased progesterone*** - The **LH surge** is triggered by a significant rise in **estrogen** levels from the dominant follicle, indicating ovarian readiness. - At the time of the LH surge, **progesterone** levels remain low; they only begin to rise significantly after ovulation, when the corpus luteum forms. *Increased estrogen & increased progesterone* - While **estrogen** levels are high, **progesterone** only significantly increases *after* ovulation, as the corpus luteum develops. - High estrogen *and* high progesterone together are typically seen in the **luteal phase**, not at the peak of the LH surge. *Decreased estrogen & increased progesterone* - A decrease in **estrogen** would suppress LH, not trigger a surge. - Increased **progesterone** would also inhibit LH release via negative feedback in the follicular phase if it were to occur pre-ovulation. *Decreased estrogen & decreased progesterone* - Both **decreased estrogen** and **decreased progesterone** would lead to low FSH/LH levels and would not promote an LH surge or ovulation. - This hormonal profile is more characteristic of the very early follicular phase or menopause.

Q: Which hormone increases with age?

Parathormone. ***Parathormone*** - **Parathormone (PTH)** levels in the blood tend to increase with age, often due to a decline in renal function and reduced vitamin D synthesis, leading to compensatory hyperparathyroidism. - This age-related increase in PTH can contribute to **bone demineralization** and an increased risk of osteoporosis. *GH* - **Growth hormone (GH)** levels generally **decrease with age**, leading to a condition known as somatopause. - Reduced GH contributes to changes in body composition, such as increased adiposity and decreased lean muscle mass, as well as reduced bone density. *Prolactin* - **Prolactin** levels typically remain relatively stable or may slightly decrease with age in men, while in women they can fluctuate due to hormonal changes like menopause but do not show a consistent increase with age. - High prolactin levels are often associated with specific pathological conditions like **prolactinomas** rather than normal aging. *Insulin* - While **insulin resistance** often increases with age, leading to higher fasting insulin levels in some individuals, the overall picture of insulin secretion can be complex and is often influenced by factors such as diet, exercise, and genetics rather than solely age. - A *decline in pancreatic beta-cell function* with age can also lead to impaired insulin secretion in some elderly individuals, complicating the simple relationship between age and insulin levels.

Q: The primary oocyte remains arrested in which stage until ovulation?

Diplotene stage. ***Diplotene stage*** - The primary oocyte enters **meiosis I** during fetal development but arrests in the **prophase I substage of diplotene**. - This arrest is maintained until **puberty** and **ovulation**, when hormonal surges trigger the completion of meiosis I. *Pachytene stage* - The **pachytene stage** of prophase I is when **crossing over** (recombination) occurs between homologous chromosomes. - While an important step in meiosis, it precedes the **diplotene arrest** point. *Metaphase* - **Metaphase** is a stage where chromosomes align at the metaphase plate, either in meiosis I or meiosis II. - The primary oocyte's arrest occurs much earlier, during **prophase I**, not metaphase. *Telophase* - **Telophase** is the final stage of mitosis or meiosis where chromosomes decondense and nuclear envelopes reform. - The oocyte's initial arrest point is in **prophase I**, long before telophase.

Q: After injecting testosterone in a hypoandrogenic male, which of the following occurs ?

Decreased FSH secretion. ***Decreased FSH secretion*** - Exogenous testosterone administration leads to **negative feedback** on the hypothalamic-pituitary-gonadal axis, suppressing **GnRH** release, which in turn decreases both **LH** and **FSH** secretion. - FSH suppression is particularly clinically significant because it results in **inhibition of spermatogenesis**, which is a key consideration when using testosterone replacement therapy. - The decrease in FSH, combined with reduced **intratesticular testosterone** (due to LH suppression), impairs Sertoli cell function and sperm production. *Decreased LH secretion* - **This also occurs** with exogenous testosterone administration due to negative feedback on the hypothalamus and pituitary. - Testosterone primarily suppresses **LH** through direct negative feedback at the hypothalamic-pituitary level. - However, in the context of this question focusing on the consequences in a hypoandrogenic male receiving testosterone, the **FSH suppression** and its impact on spermatogenesis is the more clinically emphasized outcome. - **Note:** Both LH and FSH decrease; this question likely emphasizes FSH due to its role in fertility concerns with testosterone therapy. *Increased spermatogenesis* - This is **incorrect**. Exogenous testosterone actually **suppresses spermatogenesis** through multiple mechanisms: - Decreased **FSH** (essential for Sertoli cell function) - Decreased **intratesticular testosterone** concentration (despite high systemic levels) - The high local testosterone concentration within the seminiferous tubules (30-100x serum levels) cannot be achieved by systemic testosterone alone. *None of the options* - This is incorrect because exogenous testosterone administration clearly causes **suppression of gonadotropins** (both LH and FSH) through well-established negative feedback mechanisms.

Q: In the breast, lactiferous ducts are formed under the influence of which hormone?

Estrogen. ***Estrogen*** - **Estrogen** plays a primary role in the development and branching of the **lactiferous ducts** in the breast. - It stimulates the proliferation of ductal epithelial cells, contributing to the growth of the duct system. *Progesterone* - **Progesterone** is primarily responsible for the development of the **lobuloalveolar system** and secretory differentiation within the breast. - While essential for lactation, its main function is not duct formation but rather the maturation of secretory units. *LH* - **Luteinizing hormone (LH)** is crucial for ovulation and the formation of the **corpus luteum** in the ovaries. - It has no direct role in the structural development of the lactiferous ducts in the breast. *FSH* - **Follicle-stimulating hormone (FSH)** is essential for the growth and maturation of **ovarian follicles**. - It does not directly influence the formation or development of lactiferous ducts in the breast.

Q: Which immunoglobulin is primarily secreted by the intestine?

IgA. **IgA** - **Secretory IgA** is the dominant immunoglobulin in mucosal secretions, including those of the intestine. - It plays a crucial role in providing **local immunity** by preventing microbial adherence and neutralizing toxins on mucosal surfaces. *IgG* - **IgG** is the most abundant immunoglobulin in serum and plays a major role in systemic immunity, including opsonization and complement activation. - While some IgG is found in secretions, it is not the primary immunoglobulin secreted by the intestine. *IgM* - **IgM** is a pentameric immunoglobulin, primarily found in blood and lymph, where it is very effective in activating the complement system and agglutinating antigens. - Although it can be found at mucosal surfaces in small amounts, it is not the principal secreted antibody in the intestine. *IgD* - **IgD** is primarily found on the surface of naive B lymphocytes, where it functions as a B cell receptor. - Its role in secreted form is minimal, and it is not significantly secreted into the intestine or other bodily fluids.

Question 1

Which of the following is the primary site of gastrin production?

Accepted Answer

Gastric G cells

Answer

Gastric chief cells

Answer

Pancreas

Answer

Pituitary gland

Question 2

What is the primary hormone responsible for the secretion of milk?

Accepted Answer

Prolactin

Answer

Oxytocin

Answer

Glucocorticoids

Answer

Relaxin

Question 3

Which of the following hormones is not stored in cells?

Accepted Answer

Cortisol

Answer

Thyroxin

Answer

Renin

Answer

Insulin

Question 4

LH surge is associated with?

Accepted Answer

Increased estrogen & decreased progesterone

Answer

Increased estrogen & increased progesterone

Answer

Decreased estrogen & increased progesterone

Answer

Decreased estrogen & decreased progesterone

Question 5

Which hormone increases with age?

Accepted Answer

Parathormone

Answer

GH

Answer

Prolactin

Answer

Insulin

Question 6

The primary oocyte remains arrested in which stage until ovulation?

Accepted Answer

Diplotene stage

Answer

Pachytene stage

Answer

Metaphase

Answer

Telophase

Question 7

Which of the following statements about thyroid hormone receptors is correct?

Accepted Answer

They are intracellular receptors that mediate gene transcription after binding with T3 or T4, but their primary action is through T3.

Answer

They directly bind to thyrotropin-releasing hormone (TRH)

Answer

They directly bind to thyroid-stimulating hormone (TSH)

Answer

They cause nuclear transcription after binding with T4

Question 8

After injecting testosterone in a hypoandrogenic male, which of the following occurs ?

Accepted Answer

Decreased FSH secretion

Answer

Decreased LH secretion

Answer

Increased spermatogenesis

Answer

None of the options

Question 9

In the breast, lactiferous ducts are formed under the influence of which hormone?

Accepted Answer

Estrogen

Answer

Progesterone

Answer

LH

Answer

FSH

Question 10

Which immunoglobulin is primarily secreted by the intestine?

Accepted Answer

IgA

Answer

IgG

Answer

IgM

Answer

IgD

NEET-PG 2013 — Physiology