FMGE 2019 - Physiology PYQs Practice Questions

Q: What is the principal stimulus for vasopressin secretion?

Hyperosmolality. ***Hyperosmolality*** - An increase in **plasma osmolality**, even by a small percentage (1-2%), is the **most potent and PRINCIPAL stimulus** for ADH (vasopressin) release. - This is detected by **osmoreceptors** in the hypothalamus (particularly in the organum vasculosum of the lamina terminalis), which are extremely sensitive and respond rapidly. - This response is the primary mechanism for day-to-day regulation of water balance. *Hypovolemia* - A significant decrease in **blood volume** (typically >10%) also stimulates vasopressin release, but it is **much less sensitive** than hyperosmolality and serves as a secondary/backup mechanism. - This response is mediated by **baroreceptors** in the carotid sinuses and aortic arch. - Only activated during substantial volume loss (hemorrhage, severe dehydration). *Hypoosmolality* - **Decreased plasma osmolality** actively **inhibits** vasopressin secretion as the body aims to excrete excess water. - This helps to prevent overhydration and maintain proper fluid balance. *Hypervolemia* - **Increased blood volume** (hypervolemia) **inhibits** vasopressin secretion, as the body needs to excrete excess fluid. - This contributes to diuresis and the lowering of blood pressure. [Practice more Physiology PYQs on OnCourse]

Q: NaCl symporter is present in which part of the nephron?

DCT. ***DCT*** - The **NaCl symporter** (also known as the **Na-Cl co-transporter** or NCC) is located in the **luminal membrane** of cells in the **distal convoluted tubule (DCT)**. - This transporter is responsible for reabsorbing approximately 5-10% of filtered sodium and chloride, and it is the target of **thiazide diuretics**. *PCT* - The **proximal convoluted tubule (PCT)** is responsible for bulk reabsorption of Na+ through various mechanisms, including Na+/H+ exchangers and Na+-glucose co-transporters, but not the specific NaCl symporter found in the DCT. - While significant NaCl reabsorption occurs here, it is primarily driven by different transport proteins. *Loop of Henle* - The **thick ascending limb of the loop of Henle** uses the **Na-K-2Cl co-transporter (NKCC2)** for Na+ reabsorption, which is distinct from the NaCl symporter. - This segment is the target for **loop diuretics**. *Collecting duct* - The **collecting duct** reabsorbs Na+ primarily through the **epithelial sodium channel (ENaC)**, which is regulated by aldosterone. - While reabsorption of sodium occurs, the specific NaCl symporter is not present in this segment. [Practice more Physiology PYQs on OnCourse]

Q: Which of the following causes hypoxic hypoxia?

Pneumonia. ***Pneumonia*** - Pneumonia causes **hypoxic hypoxia** by impairing **gas exchange** in the lungs due to inflammation and fluid accumulation in the alveoli, leading to reduced oxygen uptake. - This results in a **low partial pressure of oxygen (PaO2)** in the arterial blood, even with normal oxygen-carrying capacity and tissue perfusion. *HCN poisoning* - **Hydrogen cyanide (HCN) poisoning** causes **histotoxic hypoxia**, where cells are unable to utilize oxygen despite adequate delivery, by inhibiting **cytochrome c oxidase** in the electron transport chain. - It does not directly reduce the amount of oxygen in the blood or its delivery to tissues. *CO poisoning* - **Carbon monoxide (CO) poisoning** causes **anemic hypoxia** by binding to hemoglobin with a much higher affinity than oxygen, forming **carboxyhemoglobin (COHb)**. - This reduces the **oxygen-carrying capacity** of the blood and shifts the oxygen-hemoglobin dissociation curve to the left, but it is not a direct problem with alveolar gas exchange or oxygen partial pressure. *Circulatory shock* - **Circulatory shock** causes **stagnant or ischemic hypoxia**, characterized by reduced blood flow and oxygen delivery to tissues due to systemic circulatory failure. - While it results in tissue oxygen deprivation, the primary issue is impaired perfusion rather than a defect in the initial oxygenation of blood in the lungs or the blood's capacity to carry oxygen. [Practice more Physiology PYQs on OnCourse]

Q: Secretion of prolactin is inhibited by?

Dopamine. ***Dopamine*** - **Dopamine**, produced by the **hypothalamus**, is the primary physiological inhibitor of **prolactin secretion** from the anterior pituitary gland. - It acts on **D2 receptors** on lactotrophs, leading to a decrease in prolactin synthesis and release. *Serotonin* - **Serotonin** generally has a stimulatory effect on **prolactin secretion**, rather than an inhibitory one. - Elevated serotonin levels can lead to **hyperprolactinemia**. *Noradrenaline* - While **noradrenaline** can have complex effects on pituitary hormones, it is not considered the primary direct inhibitor of **prolactin secretion**. - Its influence is often indirect or less potent than that of **dopamine**. *Adrenaline* - **Adrenaline** (epinephrine) is a neurotransmitter and hormone primarily involved in the **"fight or flight" response** and does not directly inhibit **prolactin secretion**. - Its effects on pituitary hormone release are typically less direct compared to **dopamine's** specific action on lactotrophs. [Practice more Physiology PYQs on OnCourse]

Q: Which of the following has prolonged inspiratory spasms that resemble breath holding?

Apneustic breathing. ***Apneustic breathing*** - This pattern is characterized by **prolonged inspiratory pauses**, resembling breath-holding, followed by a short, insufficient expiratory phase. - It is caused by damage to the **pons** in the brainstem, often due to stroke or trauma, which disrupts the normal rhythm of breathing. *Kussmaul breathing* - Characterized by **deep**, **rapid**, and labored breathing, typically seen in metabolic acidosis like **diabetic ketoacidosis**. - It is a compensatory mechanism to increase CO2 elimination and raise blood pH. *Biot's breathing* - Involves irregular breathing with **periods of apnea** interspersed with shallow breaths. - This pattern is associated with damage to the **medulla oblongata** or severe intracranial pressure. *Cheyne-Stokes breathing* - Characterized by a **crescendo-decrescendo pattern** of respiration, where breathing gradually increases in depth and rate, then decreases, followed by a period of **apnea**. - It is often observed in **heart failure**, stroke, or severe neurological conditions, indicating brainstem or cerebral dysfunction. [Practice more Physiology PYQs on OnCourse]

Question 1

What is the principal stimulus for vasopressin secretion?

Accepted Answer

Hyperosmolality

Answer

Hypovolemia

Answer

Hypoosmolality

Answer

Hypervolemia

Question 2

NaCl symporter is present in which part of the nephron?

Accepted Answer

DCT

Answer

PCT

Answer

Loop of Henle

Answer

Collecting duct

Question 3

Which of the following causes hypoxic hypoxia?

Accepted Answer

Pneumonia

Answer

HCN poisoning

Answer

CO poisoning

Answer

Circulatory shock

Question 4

Secretion of prolactin is inhibited by?

Accepted Answer

Dopamine

Answer

Serotonin

Answer

Noradrenaline

Answer

Adrenaline

Question 5

Which of the following has prolonged inspiratory spasms that resemble breath holding?

Accepted Answer

Apneustic breathing

Answer

Kussmaul breathing

Answer

Biot breathing

Answer

Cheyne-Stokes breathing

Question 6

Testosterone is secreted by:

Accepted Answer

Leydig cell

Answer

Granulosa cell

Answer

Theca cells

Answer

Sertoli cell

Question 7

PR interval in ECG shows?

Accepted Answer

Atrial depolarization and conduction delay

Answer

Conduction through AV node

Answer

Delay in ventricular depolarization

Answer

Delay in ventricular repolarization

Question 8

Distal ileum was removed in a 20-year-old girl. Which absorption deficiency will be seen?

Accepted Answer

Bile salts

Answer

Iron

Answer

Copper

Answer

Zinc

Question 9

In this normal menstrual cycle graph, the mark 'X' represents levels of which hormone?

Accepted Answer

Progesterone

Answer

LH

Answer

FSH

Answer

Estrogen

Question 10

Normal anion gap is___ mmol/L?

Accepted Answer

8-16

Answer

30-34

Answer

20-24

Answer

0-4

FMGE 2019 — Physiology